json_view: source positions in materialize() with JSON_DIAGNOSTIC_POSITIONS

With JSON_DIAGNOSTIC_POSITIONS, materialize() now gives every value the
start_pos()/end_pos() that basic_json::parse() would give it, so exceptions
about materialized values name the same bytes (#5864).

- json_sax_dom_parser takes the lexer type as a defaulted template
  parameter; materialize() passes position_source, which reports the
  positions it derives from the index. diagnostic_positions treats npos as
  "no position" and keeps ranges all-or-nothing.
- Strings with escapes keep the offset of their opening quote plus one in
  `next` (only with the macro); materialize() scans from there to the closing
  quote. The end of an array or object is found by scanning from the end of
  its last element over whitespace, comments and a trailing comma.
- In editable documents, values written by edits, arrays and objects whose
  elements changed, and containers whose last element has no position get
  none. Images keep the flag is_new, and load() checks that `next` of a
  string is within the text.

Nothing changes on the parse path without the macro. The view's own
exceptions still carry no byte range, so the tests that compare them with
those of materialized values skip it under the macro, as they skip the path
under JSON_DIAGNOSTICS.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

docs/mkdocs/docs/api/basic_json/at.md

@@ -90,8 +90,7 @@ Strong exception safety: if an exception occurs, the original value stays intact
 1. Constant.
 2. Logarithmic in the size of the container.
 3. Logarithmic in the size of the container.
-4. Linear in the number of reference tokens of `ptr`; for each of them, logarithmic in the size of the object, or
-   constant for an array.
+4. Logarithmic in the size of the container.
 
 ## Notes
 

docs/mkdocs/docs/api/basic_json/diff.md

@@ -19,10 +19,9 @@ The equality holds up to [`operator==`](operator_eq.md), so it has the following
 - A value that is not equal to itself cannot round-trip. This applies to `NaN` (also nested in an array or object) and
   to [discarded](is_discarded.md) values: `diff` emits a `replace` operation for them. A `NaN` in the patch is
   serialized as `#!json null`, so a patch that was dumped and parsed again would set `#!json null`.
-- Numbers that compare equal produce no operation, even if their types differ or if one is zero and the other is
-  negative zero: `diff(1, 1.0)` (integer and floating-point), `diff(1u, 1)` (unsigned and signed integer) and
-  `diff(0.0, -0.0)` (positive and negative zero) all return `#!json []`. The patched value is then the `source` and
-  keeps its number type and sign.
+- Numbers that compare equal produce no operation, even if their types or signs differ: `diff(1, 1.0)`,
+  `diff(1u, 1)` (unsigned and signed integer) and `diff(0.0, -0.0)` all return `#!json []`. The patched value is then
+  the `source` and keeps its number type.
 
 ## Parameters
 

docs/mkdocs/docs/api/basic_json/operator[].md

@@ -92,20 +92,12 @@ Strong exception safety: if an exception occurs, the original value stays intact
     For the **const** version, an object key or array index in `ptr` that does not exist is not reported by an
     exception, but is undefined behavior (see the notes below). Use [`at`](at.md) for checked access.
 
-    If the **non-const** version throws, the value is left unchanged: values it created for earlier reference tokens
-    of `ptr` are removed again. This also holds for exceptions such as `#!cpp std::bad_alloc` or
-    `#!cpp std::length_error` thrown while padding an array up to a very large index. With custom
-    [template parameters](../../features/types/template_parameters.md), this requires that `erase()` of the object and
-    array types and the move operations of the custom base class do not throw.
-
 ## Complexity
 
 1. Constant if `idx` is in the range of the array. Otherwise, linear in `idx - size()`.
 2. Logarithmic in the size of the container.
 3. Logarithmic in the size of the container.
-4. Linear in the number of reference tokens of `ptr`; for each of them, logarithmic in the size of the object, or
-   constant for an array. When the non-const version pads an array with `#!json null` values, it is additionally
-   linear in `idx - size()` for that array.
+4. Logarithmic in the size of the container.
 
 ## Notes
 
@@ -153,14 +145,6 @@ Strong exception safety: if an exception occurs, the original value stays intact
         specified by the JSON Pointer RFC; it is this library's own, intentional disambiguation rule. See also
         [JSON Pointer](../../features/json_pointer.md).
 
-    !!! warning "Large array indices"
-
-        As the array is filled up with `#!json null` values to the given index, the memory used grows with the index
-        and not with the size of the pointer: on a 64-bit platform, the index `10000000` allocates about 160 MB.
-        The library does not limit the index, so check the array indices of a JSON pointer from untrusted input
-        before using it with the non-const version. See
-        [Parsing untrusted input](../../features/parsing/untrusted_input.md#json-pointers-and-flattened-keys).
-
 !!! warning "Deprecation"
 
     Overload (4) also accepts a [`json_pointer`](../json_pointer/index.md) whose template argument is a `basic_json`
@@ -312,6 +296,4 @@ Strong exception safety: if an exception occurs, the original value stays intact
 4. Added in version 2.0.0. A missing array index in the const version is guarded by a runtime assertion since
    version 3.13.0. Throws [`parse_error.109`](../../home/exceptions.md#jsonexceptionparse_error109) instead of
 [`out_of_range.404`](../../home/exceptions.md#jsonexceptionout_of_range404) for a one-character array index that is not
-a digit (e.g., `/x`) in version 3.13.0, as it already did for longer ones. Fixed in version 3.13.0 to leave the value
-unchanged if the non-const version throws (strong exception safety, as documented); before, values created for earlier
-reference tokens of `ptr` were kept.
+a digit (e.g., `/x`) in version 3.13.0, as it already did for longer ones.

docs/mkdocs/docs/api/basic_json_view/materialize.md

@@ -32,9 +32,20 @@ uses, so the result matches it exactly — including, for an object, that a repe
 last value. The replay is iterative, so it is not limited by the call stack the way a naive recursive conversion
 would be; the JSON nesting depth is limited only by available memory, as for `BasicJsonType::parse()` itself.
 
-Unlike parsing with [`JSON_DIAGNOSTIC_POSITIONS`](../macros/json_diagnostic_positions.md) enabled, the values
-produced by `materialize()` do not carry source positions. The index has the start offset of every value, but not the
-end of arrays, objects, and escaped strings, which the positions also need.
+With [`JSON_DIAGNOSTIC_POSITIONS`](../macros/json_diagnostic_positions.md) enabled, the values get the source
+positions [`BasicJsonType::parse()`](../basic_json/parse.md) would give them, also for the subtree of a view (the
+positions are those in the document's whole source text), and exceptions about them name the same bytes. For values of
+an [editable document](../json_editable_document.md), positions are all-or-nothing, and [`start_pos()`](../basic_json/start_pos.md)
+and [`end_pos()`](../basic_json/end_pos.md) return `std::string::npos` for
+
+- a value written by an edit (a copy of an array or object of the document is also new; copies of its scalars keep
+  their positions),
+- an array or object whose elements were changed (its elements keep theirs), and
+- an array or object whose last element has no positions (its end is found from that element).
+
+A `basic_json` value, in contrast, keeps its positions when it is changed. Documents [loaded](../basic_json_document/load.md)
+from an image have the positions of the saved document, except that its strings with escapes have none if it was saved
+without `JSON_DIAGNOSTIC_POSITIONS`.
 
 Calling `materialize()` on the same view repeatedly builds a new, independent `BasicJsonType` value each time; it
 never caches the result.
@@ -62,8 +73,7 @@ never caches the result.
 
 - [`root`](../basic_json_document/root.md) - the view of a document's root value
 - [`BasicJsonType::parse`](../basic_json/parse.md) - build a `BasicJsonType` value directly from a JSON text
-- [`JSON_DIAGNOSTIC_POSITIONS`](../macros/json_diagnostic_positions.md) - source positions on parsed values (not
-  produced by `materialize()`)
+- [`JSON_DIAGNOSTIC_POSITIONS`](../macros/json_diagnostic_positions.md) - source positions on parsed values
 - [Zero-copy JSON views](../../features/json_view.md#getting-values-out-without-copying) - when to build a basic_json value from a view
 
 ## Version history

docs/mkdocs/docs/api/macros/json_diagnostic_positions.md

@@ -113,6 +113,7 @@ When the macro is not defined, the library will define it to its default value.
 
 - [:simple-cmake: JSON_Diagnostic_Positions](../../integration/cmake.md#json_diagnostic_positions) - CMake option to control the macro
 - [`JSON_DIAGNOSTICS`](json_diagnostics.md) - macro to control extended diagnostics
+- [`materialize()`](../basic_json_view/materialize.md) - values of a JSON view, with the same positions
 - [Parsing and Exceptions](../../features/parsing/parse_exceptions.md) - handling parse errors and locating them in the input
 
 ## Version history

docs/mkdocs/docs/features/json_patch.md

@@ -78,9 +78,8 @@ flowchart LR
     - `NaN` and [discarded](../api/basic_json/is_discarded.md) values are not equal to themselves, so the invariant
       cannot hold for them. `diff` emits a `replace` operation for such a value, and a `NaN` in a patch is serialized
       as `#!json null`.
-    - Numbers that compare equal produce no operation even if their types differ or if one is zero and the other is
-      negative zero: `diff(1, 1.0)`, `diff(1u, 1)`, and `diff(0.0, -0.0)` return `#!json []`, so the patched value
-      keeps the number type and sign of *source*.
+    - Numbers that compare equal produce no operation even if their types differ: `diff(1, 1.0)`, `diff(1u, 1)`, and
+      `diff(0.0, -0.0)` return `#!json []`, so the patched value keeps the number type of *source*.
     - A [binary value](binary_values.md) in a patch is serialized as an object
       (`#!json {"bytes":[...],"subtype":null}`), so a patch that was dumped and parsed again no longer holds a binary
       value.

docs/mkdocs/docs/features/json_view.md

@@ -149,10 +149,12 @@ document: `#!cpp auto v = json_document::parse(text).root();` does not compile.
   end must still fit.
 - **A stream is always read to its end.** There is no partial/streaming read of an `#!cpp std::istream`: the stream
   is read to its end into a buffer the document owns, and parsing starts after that.
-- **No source positions on `materialize()`.** Even with
+- **Fewer source positions after edits.** With
   [`JSON_DIAGNOSTIC_POSITIONS`](../api/macros/json_diagnostic_positions.md) enabled,
-  [`materialize()`](../api/basic_json_view/materialize.md) does not set them. The index has the start offset of every
-  value, but not the end of arrays, objects, and escaped strings, which the positions also need.
+  [`materialize()`](../api/basic_json_view/materialize.md) sets the same positions as `#!cpp basic_json::parse()`.
+  In an [editable document](../api/json_editable_document.md), a value written by an edit has none, and neither has
+  an array or object whose elements changed or whose last element has none; a `basic_json` value keeps its positions
+  when it is changed. See [`materialize()`](../api/basic_json_view/materialize.md#notes).
 - **Objects iterate in document order.** [`begin()`](../api/basic_json_view/begin.md)/
   [`end()`](../api/basic_json_view/end.md) and [`items()`](../api/basic_json_view/items.md) visit an object's
   members in the order they appear in the source text. `basic_json`'s default `object_t` is a `std::map`, which

docs/mkdocs/docs/features/parsing/untrusted_input.md

@@ -130,17 +130,6 @@ parameters of [`parse()`](../../api/basic_json/parse.md) or [`accept()`](../../a
 enable either for input whose conformance you cannot otherwise control, since interoperability with strictly
 conforming JSON consumers is exactly what the default rejects.
 
-## JSON Pointers and flattened keys
-
-A [JSON Pointer](../json_pointer.md) can come from untrusted input as well, for instance as a path in a request or as a
-key of a flattened object. The non-const [`operator[]`](../../api/basic_json/operator%5B%5D.md) with a JSON Pointer and
-[`unflatten`](../../api/basic_json/unflatten.md) create missing values, and when an array index lies beyond the end of
-an array, they fill the array with `#!json null` values up to that index. The memory used therefore grows with the
-index, not with the size of the pointer: on a 64-bit platform, the index `10000000` allocates about 160 MB, the index
-`100000000` about 1.6 GB. The library does not limit the index. For pointers from untrusted input, check the array
-indices (or the pointer as a whole) before using them, or use [`at`](../../api/basic_json/at.md) or
-[`contains`](../../api/basic_json/contains.md), which never add values.
-
 ## Checklist
 
 - Wrap parsing in a `#!cpp try`/`#!cpp catch` block, or use `allow_exceptions=false`/`accept()` if your environment
@@ -156,8 +145,6 @@ indices (or the pointer as a whole) before using them, or use [`at`](../../api/b
   `JSON_STRICT_NUL_HANDLING`.
 - Decide whether duplicate object keys should be an error for your application, and add a callback if so.
 - Do not enable `ignore_comments` or `ignore_trailing_commas` for input that must be strictly conforming JSON.
-- Check the array indices of untrusted JSON Pointers and flattened keys before passing them to the non-const
-  `operator[]` or `unflatten()`, which fill arrays with `#!json null` values up to the index.
 
 For the broader design rationale and how it is tested (fuzzing, sanitizers, static analysis), see the
 [assurance case](../../community/assurance_case.md) and [quality assurance](../../community/quality_assurance.md). To

docs/mkdocs/docs/home/architecture.md

@@ -203,7 +203,7 @@ packet-beta
 | 2-3   | `extra` | `uint16_t` | numbers: the number of integer digits (low byte) and fraction digits (high byte), 255 for more; objects: the number of their key hash index (1-based), or 0; otherwise 0 |
 | 4-7   | `off`   | `uint32_t` | where the value starts: the first byte after a string's opening quote (or its position in the buffer of decoded strings), the first byte of a number or literal, the bracket of an array or object |
 | 8-11  | `len`   | `uint32_t` | strings: the length after decoding; floats and literals: the length of the token; arrays and objects: the number of elements |
-| 12-15 | `next`  | `uint32_t` | arrays and objects: the number of nodes of the subtree, including the node itself                                              |
+| 12-15 | `next`  | `uint32_t` | arrays and objects: the number of nodes of the subtree, including the node itself; strings with escapes: the position of the opening quote in the source plus one, or 0 (only with [`JSON_DIAGNOSTIC_POSITIONS`](../api/macros/json_diagnostic_positions.md)) |
 
 <p class="nj-table-caption" markdown>Fields of a node, by their byte offset within the 16-byte node. Integers use bytes 8-15 differently, see below.</p>
 
@@ -218,6 +218,11 @@ packet-beta
   step from element to element this way and skip whole subtrees in constant time.
 - **Offsets** are 32 bits wide, so a document is limited to 4294967279 bytes, 4 GiB minus 16 bytes (a margin below
   2^32 for positions one scanner step past the end of the text; `out_of_range.416`).
+- **Source positions** ([`JSON_DIAGNOSTIC_POSITIONS`](../api/macros/json_diagnostic_positions.md)) are derived by
+  [`materialize()`](../api/basic_json_view/materialize.md) and cost nothing while parsing: a scalar's range follows
+  from `off` and its length, a string with escapes is scanned from its opening quote (`next`) to the closing one,
+  and the end of an array or object is found by scanning from the end of its last element over whitespace, comments,
+  and a trailing comma. `materialize()` hands these positions to the SAX builder of `parse()` in place of its lexer.
 - **Large objects** (128 members or more) get a hash index for their keys after parsing
   ([`detail/view/object_index.hpp`](https://github.com/nlohmann/json/blob/develop/include/nlohmann/detail/view/object_index.hpp)):
   an open-addressing table whose slots hold the distance from the object's node to a key's node, so that a lookup does
@@ -277,7 +282,7 @@ Images ([`save`](../api/basic_json_document/save.md) and [`load`](../api/basic_j
 the nodes as they are: a 64-byte header (the magic bytes `NJVI`, a format version, the sizes, and reserved bytes that
 must be zero), the nodes, the text, and the decoded strings. An edited document is first written in document order, as
 the parser would have written it (without links), and the numbers of the hash indexes are cleared, since `load`
-rebuilds the indexes. So a change of the node layout is a change of the image format: it must raise `image_version`,
+rebuilds the indexes. The flag *new* is kept, as these values have no position in the text. So a change of the node layout is a change of the image format: it must raise `image_version`,
 and `load` then rejects images of other versions (`parse_error.116`) instead of misreading them.
 
 ## Input adapters

include/nlohmann/detail/input/json_sax.hpp

@@ -230,7 +230,10 @@ struct diagnostic_positions
         {
             // Lexer has read the first character of the container, so
             // subtract 1 from the position to get the correct start position.
-            v.start_position = lexer->get_chars_read_total() - 1;
+            // (npos: a value without a source position, see materialize() of
+            // json_view)
+            const std::size_t read = lexer->get_chars_read_total();
+            v.start_position = read == std::string::npos ? read : read - 1;
         }
     }
 
@@ -245,6 +248,12 @@ struct diagnostic_positions
         {
             // Lexer's position is past the closing brace or bracket, so set that as the end position.
             v.end_position = lexer->get_chars_read_total();
+            if (v.end_position == std::string::npos)
+            {
+                // a range has both ends or none (exception::diagnostics()
+                // prints only complete ones)
+                v.start_position = v.end_position;
+            }
         }
     }
 
@@ -261,6 +270,12 @@ struct diagnostic_positions
             // The start position will be set below based on the length of the string representation
             // of the value.
             v.end_position = lexer->get_chars_read_total();
+            if (v.end_position == std::string::npos)
+            {
+                // a value without a source position
+                v.start_position = v.end_position;
+                return;
+            }
 
             switch (v.type())
             {
@@ -473,8 +488,12 @@ read up to it.
 @tparam Collect  whether to collect the values of containers of unknown size on
                  a stack (only for a caller that does not use the value after a
                  parse error)
+@tparam LexerType  the type of the lexer that reports the source positions
+                   (JSON_DIAGNOSTIC_POSITIONS); only diagnostic_positions uses
+                   it, so any type with its three functions works (as
+                   materialize() of json_view uses it)
 */
-template<typename BasicJsonType, typename InputAdapterType, bool Collect = false>
+template<typename BasicJsonType, typename InputAdapterType, bool Collect = false, typename LexerType = lexer<BasicJsonType, InputAdapterType>>
 class json_sax_dom_parser : public json_sax_dom_error_state
 {
   public:
@@ -483,7 +502,7 @@ class json_sax_dom_parser : public json_sax_dom_error_state
     using number_float_t = typename BasicJsonType::number_float_t;
     using string_t = typename BasicJsonType::string_t;
     using binary_t = typename BasicJsonType::binary_t;
-    using lexer_t = lexer<BasicJsonType, InputAdapterType>;
+    using lexer_t = LexerType;
 
     /*!
     @param[in,out] r  reference to a JSON value that is manipulated while

include/nlohmann/detail/input/parser.hpp

@@ -56,8 +56,8 @@ using parser_callback_t =
 template<typename SAX>
 struct sax_ignores_number_text : std::false_type {};
 
-template<typename BasicJsonType, typename InputAdapterType, bool Collect>
-struct sax_ignores_number_text<json_sax_dom_parser<BasicJsonType, InputAdapterType, Collect>> : std::true_type {};
+template<typename BasicJsonType, typename InputAdapterType, bool Collect, typename LexerType>
+struct sax_ignores_number_text<json_sax_dom_parser<BasicJsonType, InputAdapterType, Collect, LexerType>> : std::true_type {};
 
 template<typename BasicJsonType, typename InputAdapterType>
 struct sax_ignores_number_text<json_sax_dom_callback_parser<BasicJsonType, InputAdapterType>> : std::true_type {};

include/nlohmann/detail/json_pointer.hpp

@@ -8,7 +8,7 @@
 
 #pragma once
 
-#include <algorithm> // copy
+#include <algorithm> // all_of, copy
 #include <array> // array
 #include <cctype> // isdigit
 #include <cerrno> // errno, ERANGE
@@ -16,11 +16,9 @@
 #include <cstdint> // uint64_t
 #include <cstdlib> // strtoull
 #include <cstring> // memchr, memcmp, memcpy
-#include <functional> // less
 #ifndef JSON_NO_IO
     #include <iosfwd> // ostream
 #endif  // JSON_NO_IO
-#include <iterator> // next
 #include <limits> // max
 #include <string> // string
 #include <utility> // move
@@ -30,7 +28,6 @@
 #include <nlohmann/detail/macro_scope.hpp>
 #include <nlohmann/detail/meta/cpp_future.hpp>
 #include <nlohmann/detail/meta/type_traits.hpp>
-#include <nlohmann/detail/meta/void_t.hpp>
 #include <nlohmann/detail/string_concat.hpp>
 #include <nlohmann/detail/string_escape.hpp>
 #include <nlohmann/detail/string_utils.hpp>
@@ -137,26 +134,6 @@ JSON_HEDLEY_ALWAYS_INLINE array_index_status parse_array_index(const StringType&
     return array_index_status::ok;
 }
 
-/// whether two keys of type @a StringType are equivalent under @a Compare
-/// exactly if they are equal: std::less<StringType> and std::less<>
-template<typename Compare, typename StringType>
-struct is_less_comparator : std::false_type {};
-
-template<typename StringType>
-struct is_less_comparator<std::less<StringType>, StringType> : std::true_type {};
-
-template<typename StringType>
-struct is_less_comparator<std::less<void>, StringType> : std::true_type {};
-
-/// whether the objects of type @a ObjectType find a key of type @a StringType
-/// exactly if it equals a stored key
-template<typename ObjectType, typename StringType, typename = void>
-struct finds_equal_keys : std::false_type {};
-
-template<typename ObjectType, typename StringType>
-struct finds_equal_keys<ObjectType, StringType, void_t<typename ObjectType::key_compare, typename ObjectType::key_type>>
-    : conjunction<is_less_comparator<typename ObjectType::key_compare, StringType>, std::is_same<typename ObjectType::key_type, StringType>> {};
-
 }  // namespace detail
 
 /// @brief JSON Pointer defines a string syntax for identifying a specific value within a JSON document
@@ -612,225 +589,6 @@ class json_pointer
         return object_member_impl(object, key, detail::priority_tag<1> {});
     }
 
-    /// @brief append a null value to @a array, like operator[] with the size of @a array
-    template<typename BasicJsonType>
-    static BasicJsonType& array_append(BasicJsonType& array)
-    {
-        auto& elements = *array.m_data.m_value.array;
-        const auto old_capacity = array.container_capacity();
-        elements.emplace_back();
-        return array.set_parent_after_insert(elements.back(), old_capacity);
-    }
-
-    /// @brief add @a key, which is missing, to @a object
-    template<typename BasicJsonType>
-    static auto object_add_impl(BasicJsonType& object, const string_t& key, detail::priority_tag<1> /*unused*/)
-    -> decltype(object.m_data.m_value.object->emplace(key, nullptr), std::declval<BasicJsonType&>())
-    {
-        const auto old_capacity = object.container_capacity();
-        const auto it = object.m_data.m_value.object->emplace(key, nullptr).first;
-        return object.set_parent_after_insert(it->second, old_capacity);
-    }
-
-    template<typename BasicJsonType>
-    static BasicJsonType& object_add_impl(BasicJsonType& object, const string_t& key, detail::priority_tag<0> /*unused*/)
-    {
-        return object.operator[](key);
-    }
-
-    template<typename BasicJsonType>
-    static BasicJsonType& object_add(BasicJsonType& object, const string_t& key)
-    {
-        return object_add_impl(object, key, detail::priority_tag<1> {});
-    }
-
-    /// @brief search @a key in @a members: the result is where the key is or,
-    /// for objects that can insert at a position (std::map), where it belongs
-    template<typename ObjectType>
-    static auto object_search_impl(ObjectType& members, const string_t& key, detail::priority_tag<1> /*unused*/)
-    -> decltype(members.key_comp()(key, members.lower_bound(key)->first), members.lower_bound(key))
-    {
-        return members.lower_bound(key);
-    }
-
-    template<typename ObjectType>
-    static auto object_search_impl(ObjectType& members, const string_t& key, detail::priority_tag<0> /*unused*/)
-    -> decltype(members.find(key))
-    {
-        return members.find(key);
-    }
-
-    template<typename ObjectType>
-    static auto object_search(ObjectType& members, const string_t& key)
-    -> decltype(object_search_impl(members, key, detail::priority_tag<1> {}))
-    {
-        return object_search_impl(members, key, detail::priority_tag<1> {});
-    }
-
-    /// @brief whether @a it, the result of @ref object_search for @a key, points to @a key
-    ///
-    /// With std::less, the key at the lower bound is equivalent to @a key
-    /// exactly if it is equal to it, and comparing for equality is cheaper.
-    template<typename ObjectType, typename Iterator,
-             detail::enable_if_t<detail::finds_equal_keys<ObjectType, string_t>::value, int> = 0>
-    static auto object_search_found_impl(ObjectType& members, const Iterator& it, const string_t& key, detail::priority_tag<2> /*unused*/)
-    -> decltype(members.lower_bound(key), it->first == key)
-    {
-        return it != members.end() && it->first == key;
-    }
-
-    template<typename ObjectType, typename Iterator>
-    static auto object_search_found_impl(ObjectType& members, const Iterator& it, const string_t& key, detail::priority_tag<1> /*unused*/)
-    -> decltype(members.key_comp()(key, it->first), members.lower_bound(key), bool())
-    {
-        return it != members.end() && !members.key_comp()(key, it->first);
-    }
-
-    template<typename ObjectType, typename Iterator>
-    static bool object_search_found_impl(ObjectType& members, const Iterator& it, const string_t& /*key*/, detail::priority_tag<0> /*unused*/)
-    {
-        return it != members.end();
-    }
-
-    template<typename ObjectType, typename Iterator>
-    static bool object_search_found(ObjectType& members, const Iterator& it, const string_t& key)
-    {
-        return object_search_found_impl(members, it, key, detail::priority_tag<2> {});
-    }
-
-    /// @brief insert @a key, which is missing, into @a object at @a it, the
-    /// result of @ref object_search for @a key
-    template<typename BasicJsonType, typename Iterator>
-    static auto object_insert_impl(BasicJsonType& object, const Iterator& it, const string_t& key, detail::priority_tag<1> /*unused*/)
-    -> decltype(object.m_data.m_value.object->emplace_hint(it, key, nullptr), std::declval<BasicJsonType&>())
-    {
-        const auto old_capacity = object.container_capacity();
-        const auto pos = object.m_data.m_value.object->emplace_hint(it, key, nullptr);
-        return object.set_parent_after_insert(pos->second, old_capacity);
-    }
-
-    template<typename BasicJsonType, typename Iterator>
-    static BasicJsonType& object_insert_impl(BasicJsonType& object, const Iterator& /*it*/, const string_t& key, detail::priority_tag<0> /*unused*/)
-    {
-        return object_add(object, key);
-    }
-
-    template<typename BasicJsonType, typename Iterator>
-    static BasicJsonType& object_insert(BasicJsonType& object, const Iterator& it, const string_t& key)
-    {
-        return object_insert_impl(object, it, key, detail::priority_tag<1> {});
-    }
-
-    /*!
-    @brief undoes the change @ref get_unchecked_create made to an existing value
-
-    @ref get_unchecked walks existing values without changing them. At the
-    first reference token that does not select an existing value, @ref
-    get_unchecked_create makes exactly one change to an existing value: it
-    converts a null value, inserts a key into an object, or grows an array.
-    Everything it creates afterwards lies below that change. If a later step
-    throws, the destructor of this guard reverts that one change, which
-    removes everything created after it, so the value is left as it was
-    (strong exception safety). The guard needs no try/catch and therefore also
-    compiles with JSON_NOEXCEPTION.
-
-    Reverting the change must not throw, as it happens in a destructor. It
-    erases the inserted member by its iterator (no key is converted or
-    compared, nothing is allocated), erases the added elements at the end of
-    the array, or swaps the null value back. This holds for std::map,
-    std::vector, ordered_map, and every object_t, array_t, and
-    json_base_class_t whose erase() and move operations do not throw.
-    Between recording and reverting, nothing is inserted into or erased from
-    the object or array, so the iterator stays valid.
-    */
-    template<typename BasicJsonType>
-    class get_unchecked_rollback
-    {
-      public:
-        using object_iterator = typename BasicJsonType::object_t::iterator;
-
-        /// record that @a member was inserted into the object @a value
-        get_unchecked_rollback(BasicJsonType* value, const object_iterator& member)
-            : m_value(value)
-            , m_member(member)
-            , m_change(change::key_inserted)
-        {}
-
-        /// record the change that the next reference token makes to the null value or array @a value
-        explicit get_unchecked_rollback(BasicJsonType* value)
-            : m_value(value)
-        {
-            if (value->is_null())
-            {
-                // keep the null value (with its base class and positions) and
-                // continue with a fresh null value in its place, which is what
-                // assigning an array or object to it would have left there
-                m_saved_null.swap(*value);
-                m_change = change::null_converted;
-            }
-            else
-            {
-                JSON_ASSERT(value->is_array());
-                m_old_size = value->m_data.m_value.array->size();
-                m_change = change::array_grown;
-            }
-        }
-
-        get_unchecked_rollback(const get_unchecked_rollback&) = delete;
-        get_unchecked_rollback(get_unchecked_rollback&&) = delete;
-        get_unchecked_rollback& operator=(const get_unchecked_rollback&) = delete;
-        get_unchecked_rollback& operator=(get_unchecked_rollback&&) = delete;
-
-        ~get_unchecked_rollback()
-        {
-            undo();
-        }
-
-        /// keep the change
-        void commit() noexcept
-        {
-            m_change = change::none;
-        }
-
-      private:
-        void undo() noexcept
-        {
-            switch (m_change)
-            {
-                case change::null_converted:
-                    // the values created since go away with m_saved_null
-                    m_value->swap(m_saved_null);
-                    break;
-                case change::key_inserted:
-                    m_value->m_data.m_value.object->erase(m_member);
-                    break;
-                case change::array_grown:
-                {
-                    auto& elements = *m_value->m_data.m_value.array;
-                    elements.resize(m_old_size);
-                    break;
-                }
-                case change::none:
-                default:
-                    break;
-            }
-        }
-
-        enum class change
-        {
-            none,
-            null_converted,
-            key_inserted,
-            array_grown
-        };
-
-        BasicJsonType* m_value;
-        object_iterator m_member {};
-        typename BasicJsonType::size_type m_old_size = 0;
-        change m_change = change::none;
-        BasicJsonType m_saved_null {};
-    };
-
   JSON_PRIVATE_UNLESS_TESTED:
     json_pointer top() const
     {
@@ -1214,245 +972,47 @@ class json_pointer
 
     Complexity: Linear in the length of the JSON pointer.
 
-    Exception safety: Strong guarantee. This function walks existing values
-    until the first reference token that does not select one. If that is the
-    last reference token, inserting the key into the object or growing the
-    array is strongly exception safe by itself; any other change is made by
-    @ref get_unchecked_create, which undoes it if a later step throws.
-
-    @throw parse_error.106   if an array index of an existing array begins with '0'
-    @throw parse_error.109   if an array index of an existing array was not a number
-    @throw out_of_range.404  if the JSON pointer can not be resolved, or if an
-                             array index is too large for strtoull
-    @throw out_of_range.410  if an array index exceeds size_type
-    @throw std::length_error if padding an array exceeds its maximal size
-    @throw std::bad_alloc    if an allocation fails
+    @throw parse_error.106   if an array index begins with '0'
+    @throw parse_error.109   if an array index was not a number
+    @throw out_of_range.404  if the JSON pointer can not be resolved
     */
     template<typename BasicJsonType>
     BasicJsonType& get_unchecked(BasicJsonType* ptr) const
     {
-        const auto* token = reference_tokens.data();
-        const auto* const end = token + reference_tokens.size();
-        if (token == end)
+        for (const auto& reference_token : reference_tokens)
         {
-            return *ptr;
-        }
-        if (ptr->is_null())
-        {
-            // the null value is converted to an array or an object
-            return get_unchecked_create(ptr, token, end);
-        }
-
-        // walk existing values; the walk itself inserts nothing, which keeps
-        // the loop fast (insertions are done below or in get_unchecked_create)
-        typename BasicJsonType::object_t::iterator it;
-        do
-        {
-            if (ptr->is_object())
-            {
-                auto& members = *ptr->m_data.m_value.object;
-                it = object_search(members, *token);
-                if (!object_search_found(members, it, *token))
-                {
-                    // the key is inserted below or in get_unchecked_create
-                    break;
-                }
-                ptr = &it->second;
-            }
-            else if (ptr->is_array())
-            {
-                if (is_dash(*token))
-                {
-                    if (token + 1 == end)
-                    {
-                        // explicitly treat "-" as index beyond the end
-                        return array_append(*ptr);
-                    }
-                    // an element will be appended in get_unchecked_create
-                    break;
-                }
-                if (token + 1 == end)
-                {
-                    // convert array index to number; unchecked access
-                    return ptr->operator[](array_index<BasicJsonType>(*token));
-                }
-                const auto idx = array_index<BasicJsonType>(*token);
-                if (idx >= ptr->m_data.m_value.array->size())
-                {
-                    // the array will be padded in get_unchecked_create
-                    break;
-                }
-                ptr = &(*ptr->m_data.m_value.array)[idx];
-            }
-            else if (ptr->is_null())
-            {
-                // the null value will be converted in get_unchecked_create
-                break;
-            }
-            else
-            {
-                // primitive value with a reference token left
-                throw_unresolved(*token, ptr);
-            }
-        }
-        while (++token != end);
-
-        if (token == end)
-        {
-            return *ptr;
-        }
-        if (token + 1 == end && ptr->is_object())
-        {
-            // insert the missing key where the walk found it belongs
-            return object_insert(*ptr, it, *token);
-        }
-        return get_unchecked_create(ptr, token, end);
-    }
-
-    /*!
-    @brief create the values for the reference tokens from @a first on
-
-    Continues @ref get_unchecked at the first reference token that does not
-    select an existing value. That token changes @a ptr, an existing value (see
-    @ref get_unchecked_rollback); all later tokens only change values created
-    here.
-
-    If the emplace() of the object type finds a member that the lookup in @ref
-    get_unchecked did not find (the two disagree, e.g. for fifo_map), nothing
-    is inserted, and the walk continues with that member as in @ref
-    get_unchecked, which is what basic_json::operator[] does.
-
-    @param[in] ptr    the value the reference token @a first is applied to
-    @param[in] first  the first reference token to resolve (an element of
-                      @ref reference_tokens)
-    @param[in] end    the end of @ref reference_tokens
-
-    @throw parse_error.106   if an array index of an existing array begins with
-                             '0' (only after emplace() found a member, see above)
-    @throw parse_error.109   if an array index of an existing array was not a
-                             number (only after emplace() found a member)
-    @throw out_of_range.404  if an array index is too large for strtoull, or (only
-                             after emplace() found a member) if the JSON pointer
-                             can not be resolved
-    @throw out_of_range.410  if an array index exceeds size_type
-    @throw std::length_error if padding an array exceeds its maximal size
-    @throw std::bad_alloc    if an allocation fails
-    */
-    template<typename BasicJsonType>
-    JSON_HEDLEY_NEVER_INLINE static BasicJsonType& get_unchecked_create(BasicJsonType* ptr, const string_t* first, const string_t* end)
-    {
-        const auto* token = first;
-        while (ptr->is_object())
-        {
-            const auto old_capacity = ptr->container_capacity();
-            const auto inserted = ptr->m_data.m_value.object->emplace(*token, nullptr);
-            if (JSON_HEDLEY_LIKELY(inserted.second))
-            {
-                get_unchecked_rollback<BasicJsonType> rollback(ptr, inserted.first);
-                BasicJsonType& result = create_values(&ptr->set_parent_after_insert(inserted.first->second, old_capacity), token + 1, end);
-                rollback.commit();
-                return result;
-            }
-
-            // nothing was inserted: walk existing values from the member
-            // emplace() found on, like get_unchecked
-            ptr = &inserted.first->second;
-            while (++token != end)
-            {
-                if (ptr->is_object())
-                {
-                    auto& members = *ptr->m_data.m_value.object;
-                    const auto it = object_search(members, *token);
-                    if (!object_search_found(members, it, *token))
-                    {
-                        break;
-                    }
-                    ptr = &it->second;
-                }
-                else if (ptr->is_array())
-                {
-                    if (is_dash(*token))
-                    {
-                        break;
-                    }
-                    const auto idx = array_index<BasicJsonType>(*token);
-                    if (idx >= ptr->m_data.m_value.array->size())
-                    {
-                        break;
-                    }
-                    ptr = &(*ptr->m_data.m_value.array)[idx];
-                }
-                else if (ptr->is_null())
-                {
-                    break;
-                }
-                else
-                {
-                    // primitive value with a reference token left
-                    throw_unresolved(*token, ptr);
-                }
-            }
-            if (token == end)
-            {
-                return *ptr;
-            }
-        }
-
-        get_unchecked_rollback<BasicJsonType> rollback(ptr);
-        BasicJsonType& result = create_values(ptr, token, end);
-        rollback.commit();
-        return result;
-    }
-
-    /*!
-    @brief the loop of @ref get_unchecked_create
-
-    @a ptr is a null value or an array. Every value created here is a fresh
-    one, so every object a key is added to is empty.
-
-    @throw out_of_range.404  if an array index is too large for strtoull
-    @throw out_of_range.410  if an array index exceeds size_type
-    @throw std::length_error if padding an array exceeds its maximal size
-    @throw std::bad_alloc    if an allocation fails
-    */
-    template<typename BasicJsonType>
-    static BasicJsonType& create_values(BasicJsonType* ptr, const string_t* first, const string_t* end)
-    {
-        for (const auto* token = first; token != end; ++token)
-        {
-            const auto& reference_token = *token;
-
             // convert null values to arrays or objects before continuing
             if (ptr->is_null())
             {
-                // change value to an array for array indices or "-" or to an
-                // object otherwise; every null value here is a fresh one (see
-                // get_unchecked_rollback), so converting it in place leaves
-                // the same value as assigning an array or object to it
-                if (is_array_index_token(reference_token) || is_dash(reference_token))
+                // check if the reference token is a valid array index, that is
+                // a nonempty sequence of digits without a leading '0'
+                // (cf. RFC 6901, Sect. 4); tokens that could never be a valid
+                // array index (such as "01" or "") are treated as object keys
+                const bool nums = !reference_token.empty()
+                                  && (reference_token.size() == 1 || reference_token[0] != '0')
+                                  && std::all_of(reference_token.begin(), reference_token.end(),
+                                                 [](const unsigned char x)
                 {
-                    ptr->template convert_null_to<typename BasicJsonType::array_t>();
-                }
-                else
-                {
-                    ptr->template convert_null_to<typename BasicJsonType::object_t>();
-                }
+                    return std::isdigit(x);
+                });
+
+                // change value to an array for array indices or "-" or to object otherwise
+                *ptr = (nums || reference_token == "-")
+                       ? detail::value_t::array
+                       : detail::value_t::object;
             }
 
             if (ptr->is_object())
             {
-                // the object is new and empty
-                ptr = &object_add(*ptr, reference_token);
+                // use unchecked object access
+                ptr = &object_member(*ptr, reference_token);
             }
-            else
+            else if (ptr->is_array())
             {
-                // only the first value is not created here, and it is a null
-                // value or an array (see get_unchecked_create)
-                JSON_ASSERT(ptr->is_array());
-                if (is_dash(reference_token))
+                if (reference_token == "-")
                 {
                     // explicitly treat "-" as index beyond the end
-                    ptr = &array_append(*ptr);
+                    ptr = &ptr->operator[](ptr->m_data.m_value.array->size());
                 }
                 else
                 {
@@ -1460,31 +1020,16 @@ class json_pointer
                     ptr = &ptr->operator[](array_index<BasicJsonType>(reference_token));
                 }
             }
+            else
+            {
+                // primitive value with a reference token left
+                throw_unresolved(reference_token, ptr);
+            }
         }
 
         return *ptr;
     }
 
-    /// whether @a s is a valid array index, that is a nonempty sequence of
-    /// digits without a leading '0' (cf. RFC 6901, Sect. 4); tokens that could
-    /// never be a valid array index (such as "01" or "") are object keys
-    static bool is_array_index_token(const string_t& s)
-    {
-        const std::size_t size = s.size();
-        if (size == 0 || (size > 1 && s[0] == '0'))
-        {
-            return false;
-        }
-        for (std::size_t i = 0; i < size; ++i)
-        {
-            if (std::isdigit(static_cast<unsigned char>(s[i])) == 0)
-            {
-                return false;
-            }
-        }
-        return true;
-    }
-
     /*!
     @throw parse_error.106   if an array index begins with '0'
     @throw parse_error.109   if an array index was not a number

include/nlohmann/detail/view/builder.hpp

@@ -1193,7 +1193,13 @@ indent_done:
                 return false;
             }
             p = r.p;
+#if JSON_DIAGNOSTIC_POSITIONS
+            // the decoded string is in the arena: next keeps the source offset
+            // of the opening quote plus one (0: unknown) for materialize()
+            push_node(node_kind::string, node_flags::escaped, 0, r.start, static_cast<std::uint64_t>(r.len) | (static_cast<std::uint64_t>(s - b) << 32));
+#else
             push_node(node_kind::string, node_flags::escaped, 0, r.start, r.len);
+#endif
             return true;
         }
     };

include/nlohmann/detail/view/image.hpp

@@ -80,7 +80,8 @@ constexpr std::uint64_t image_limit = 0xFFFFFFF0u;
 /// Copy the current structure of an edited document into nodes in document
 /// order, as the parser would have written them. Text written by edits is
 /// appended to text_tail (number tokens) and arena_tail (strings); floats that
-/// are not finite become null, as dump() writes them.
+/// are not finite become null, as dump() writes them. Nodes keep the flag
+/// is_new: they have no source position (JSON_DIAGNOSTIC_POSITIONS).
 inline void compact_nodes(const document_data& d, std::size_t arena_size, std::vector<node>& out, std::string& text_tail, std::string& arena_tail)
 {
     struct frame
@@ -103,16 +104,18 @@ inline void compact_nodes(const document_data& d, std::size_t arena_size, std::v
             arena_tail.append(d.str(s), s.len);
             r.flags = node_flags::escaped;
         }
+        r.flags = static_cast<std::uint8_t>(r.flags | (s.flags & node_flags::is_new));
         return r;
     };
     const auto copy_node = [&](const node * v)
     {
         node r = *v;
+        const auto is_new = static_cast<std::uint8_t>(v->flags & node_flags::is_new);
         switch (static_cast<value_t>(v->kind))
         {
             case value_t::object:
             case value_t::array:
-                r.flags = 0;
+                r.flags = is_new;
                 r.extra = 0;
                 r.off = (v->flags & (node_flags::moved | node_flags::is_new)) != 0 ? 0 : v->off;
                 r.len = 0;  // counted below
@@ -129,7 +132,7 @@ inline void compact_nodes(const document_data& d, std::size_t arena_size, std::v
                     r.off = static_cast<std::uint32_t>(d.size + text_tail.size());
                     text_tail.append(d.str(*v), number_length(*v));
                 }
-                r.flags = 0;
+                r.flags = is_new;
                 break;
             case value_t::number_float:
                 if ((v->flags & node_flags::storage) == node_flags::edited)
@@ -139,22 +142,23 @@ inline void compact_nodes(const document_data& d, std::size_t arena_size, std::v
                     {
                         r = node{}; // nan and infinity: null, as dump() writes them
                         r.kind = node_kind::null;
+                        r.flags = is_new;
                         break;
                     }
                     r.off = static_cast<std::uint32_t>(d.size + text_tail.size());
                     text_tail.append(t, v->len);
                     r.extra = 0xFFFFu; // the digit layout is not recorded
                 }
-                r.flags = 0;
+                r.flags = is_new;
                 break;
             case value_t::boolean:
-                r.flags = static_cast<std::uint8_t>(v->flags & node_flags::is_true);
+                r.flags = static_cast<std::uint8_t>(v->flags & (node_flags::is_true | node_flags::is_new));
                 break;
             case value_t::null:
             case value_t::binary:
             case value_t::discarded:
             default:
-                r.flags = 0;
+                r.flags = is_new;
                 break;
         }
         out.push_back(r);
@@ -515,13 +519,15 @@ inline bool check_image(const node* nodes, std::size_t count, const unsigned cha
     std::vector<float_range> floats;
     const auto check_string = [&](const node & n) -> bool
     {
-        if ((n.flags & ~node_flags::escaped) != 0 || n.extra != 0)
+        if ((n.flags & ~(node_flags::escaped | node_flags::is_new)) != 0 || n.extra != 0)
         {
             return false;
         }
         const bool decoded = (n.flags & node_flags::escaped) != 0;
         const std::size_t limit = decoded ? arena_size : text_size;
-        if (n.off > limit || n.len > limit - n.off)
+        // (next: the source offset of a decoded string's opening quote plus
+        // one, or 0; see node)
+        if (n.off > limit || n.len > limit - n.off || n.next > text_size)
         {
             return false;
         }
@@ -593,13 +599,13 @@ inline bool check_image(const node* nodes, std::size_t count, const unsigned cha
         {
             case value_t::null:
                 // (the offset of a literal is read to size the output of dump())
-                if (n.flags != 0 || n.extra != 0 || n.off > text_size)
+                if ((n.flags & ~node_flags::is_new) != 0 || n.extra != 0 || n.off > text_size)
                 {
                     return false;
                 }
                 break;
             case value_t::boolean:
-                if ((n.flags & ~node_flags::is_true) != 0 || n.extra != 0 || n.off > text_size)
+                if ((n.flags & ~(node_flags::is_true | node_flags::is_new)) != 0 || n.extra != 0 || n.off > text_size)
                 {
                     return false;
                 }
@@ -613,7 +619,7 @@ inline bool check_image(const node* nodes, std::size_t count, const unsigned cha
             case value_t::number_integer:
             case value_t::number_unsigned:
             case value_t::number_float:
-                if (n.flags != 0 || !number_in_bounds(n))
+                if ((n.flags & ~node_flags::is_new) != 0 || !number_in_bounds(n))
                 {
                     return false;
                 }
@@ -635,7 +641,7 @@ inline bool check_image(const node* nodes, std::size_t count, const unsigned cha
             case value_t::object:
             {
                 const std::size_t limit = stack.empty() ? count : stack.back().end;
-                if (n.flags != 0 || n.extra != 0 || n.next == 0 || n.next > limit - i || n.off > text_size)
+                if ((n.flags & ~node_flags::is_new) != 0 || n.extra != 0 || n.next == 0 || n.next > limit - i || n.off > text_size)
                 {
                     return false;
                 }

include/nlohmann/detail/view/materialize.hpp

@@ -26,6 +26,176 @@ namespace detail
 namespace view
 {
 
+#if JSON_DIAGNOSTIC_POSITIONS
+/*!
+@brief the source positions of the values materialize() replays
+
+Stands in for the lexer of json_sax_dom_parser, which reads the positions of
+the values it stores from these three functions (diagnostic_positions). npos
+is a value without a source position.
+*/
+struct position_source
+{
+    /// the token, of which diagnostic_positions only reads the length
+    struct token
+    {
+        std::size_t length;
+        std::size_t size() const noexcept
+        {
+            return length;
+        }
+    };
+
+    std::size_t start = std::string::npos; ///< the first byte of the next value
+    std::size_t end = std::string::npos;   ///< one past the next value (start_object/start_array: one past the bracket)
+
+    std::size_t get_chars_read_total() const noexcept
+    {
+        return end;
+    }
+    std::size_t get_token_start_position() const noexcept
+    {
+        return start;
+    }
+    token get_string() const noexcept
+    {
+        return token{end - start};
+    }
+
+    /// the range [first, last), or none if either is npos
+    void set(std::size_t first, std::size_t last) noexcept
+    {
+        const bool known = first != std::string::npos && last != std::string::npos;
+        start = known ? first : std::string::npos;
+        end = known ? last : std::string::npos;
+    }
+
+    /// one past the closing quote of the string whose opening quote is at
+    /// src[quote], or npos (the scan is bounded by size, as images can be
+    /// loaded without a check)
+    static std::size_t string_end(const char* src, std::size_t size, std::size_t quote) noexcept
+    {
+        for (std::size_t i = quote + 1; i < size; ++i)
+        {
+            if (src[i] == '\\')
+            {
+                ++i;
+            }
+            else if (src[i] == '"')
+            {
+                return i + 1;
+            }
+        }
+        return std::string::npos;
+    }
+
+    /// one past the closing bracket of the array or object whose last element
+    /// ends at src[pos] (or whose opening bracket is at src[pos - 1]), or npos;
+    /// in between, there can only be whitespace, comments, and a trailing comma
+    /// (the source was validated when it was parsed)
+    static std::size_t container_end(const char* src, std::size_t size, std::size_t pos) noexcept
+    {
+        while (pos < size)
+        {
+            switch (src[pos])
+            {
+                case ' ':
+                case '\t':
+                case '\n':
+                case '\r':
+                case ',':
+                    ++pos;
+                    break;
+                case ']':
+                case '}':
+                    return pos + 1;
+                case '/':
+                    if (pos + 1 < size && src[pos + 1] == '/')
+                    {
+                        pos += 2;
+                        while (pos < size && src[pos] != '\n' && src[pos] != '\r')
+                        {
+                            ++pos;
+                        }
+                        break;
+                    }
+                    if (pos + 1 < size && src[pos + 1] == '*')
+                    {
+                        pos += 2;
+                        while (pos < size && !(src[pos] == '*' && pos + 1 < size && src[pos + 1] == '/'))
+                        {
+                            ++pos;
+                        }
+                        pos += 2;
+                        break;
+                    }
+                    return std::string::npos;
+                default:
+                    return std::string::npos;
+            }
+        }
+        return std::string::npos;
+    }
+
+    /// the range of the scalar n of document d
+    void set_scalar(const document_data& d, const node& n) noexcept
+    {
+        const std::size_t size = d.size;
+        const std::size_t off = n.off;
+        std::size_t first = std::string::npos;
+        std::size_t last = std::string::npos;
+        if ((n.flags & node_flags::is_new) == 0)
+        {
+            switch (static_cast<value_t>(n.kind))
+            {
+                case value_t::string:
+                    if ((n.flags & node_flags::storage) == 0)
+                    {
+                        // off is the first byte after the opening quote
+                        if (off != 0)
+                        {
+                            first = off - 1;
+                            last = off + std::size_t{n.len} + 1;
+                        }
+                    }
+                    else if ((n.flags & node_flags::storage) == node_flags::escaped && n.next != 0)
+                    {
+                        // next is the offset of the opening quote plus one
+                        first = n.next - 1;
+                        last = string_end(d.base[0], size, first);
+                    }
+                    break;
+                case value_t::number_integer:
+                case value_t::number_unsigned:
+                case value_t::number_float:
+                    if ((n.flags & node_flags::storage) == 0)
+                    {
+                        first = off;
+                        last = off + number_length(n);
+                    }
+                    break;
+                case value_t::boolean:
+                    first = off;
+                    last = off + ((n.flags & node_flags::is_true) != 0 ? 4u : 5u);
+                    break;
+                case value_t::null:
+                    first = off;
+                    last = off + 4u;
+                    break;
+                case value_t::object:
+                case value_t::array:
+                case value_t::binary:
+                case value_t::discarded:
+                default:
+                    break;
+            }
+        }
+        // (a crafted image can point past the text)
+        set(first, last != std::string::npos && last <= size ? last : std::string::npos);
+    }
+};
+#endif
+
 /*!
 @brief the basic_json value of the subtree at n
 
@@ -33,14 +203,22 @@ The subtree is replayed into the SAX handler that parse() uses to build its
 values, so the result is the value parse() would produce: duplicate keys keep
 the last value, and with JSON_DIAGNOSTICS the parent pointers are set. It is
 iterative, so the nesting depth is limited by memory only, as for parse().
-Without a lexer the handler records no source positions
-(JSON_DIAGNOSTIC_POSITIONS).
+
+With JSON_DIAGNOSTIC_POSITIONS, the values get their source positions as with
+parse(): position_source stands in for the lexer. Values written by edits have
+none (npos), and neither has an array or object whose elements changed, or
+whose last element has none (the end of its closing bracket is found by
+scanning from the end of the last element).
 */
 template<typename BasicJsonType, bool Editable>
 BasicJsonType materialize(const document_data& d, const node* n)
 {
     using string_t = typename BasicJsonType::string_t;
+#if JSON_DIAGNOSTIC_POSITIONS
+    using sax_t = json_sax_dom_parser<BasicJsonType, iterator_input_adapter<const char*>, true, position_source>;
+#else
     using sax_t = json_sax_dom_parser<BasicJsonType, iterator_input_adapter<const char*>, true>;
+#endif
     using nav = navigation<Editable>;
 
     // the open containers: their next element (or key of the next member),
@@ -52,9 +230,15 @@ BasicJsonType materialize(const document_data& d, const node* n)
         const node* pos;
         const node* end;
         bool object;
+#if JSON_DIAGNOSTIC_POSITIONS
+        std::size_t start;    ///< the opening bracket (npos: unknown)
+        std::size_t last_end; ///< the end of the last element read (npos: unknown)
+#endif
     };
 
+#if !JSON_DIAGNOSTIC_POSITIONS
     // a scalar needs neither the handler nor the stack of open containers
+    // (with positions, it goes through the handler, which sets them)
     switch (static_cast<value_t>(n->kind))
     {
         case value_t::string:
@@ -76,9 +260,15 @@ BasicJsonType materialize(const document_data& d, const node* n)
         default:
             break;
     }
+#endif
 
     BasicJsonType result;
+#if JSON_DIAGNOSTIC_POSITIONS
+    position_source positions;
+    sax_t sax(result, true, &positions);
+#else
     sax_t sax(result, true);
+#endif
     const string_t no_token {};
     // (shallow subtrees on the stack: a call for a small value then allocates only for the value)
     std::array<frame, 16> shallow; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): filled as containers open
@@ -94,6 +284,16 @@ BasicJsonType materialize(const document_data& d, const node* n)
     std::size_t depth = 0;
     for (;;)
     {
+#if JSON_DIAGNOSTIC_POSITIONS
+        if (!is_container(*n))
+        {
+            positions.set_scalar(d, *n);
+            if (depth != 0)
+            {
+                open[depth - 1].last_end = positions.end;
+            }
+        }
+#endif
         // false positive: n comes from nav::value(), which never returns null for a valid index
         // @infer-ignore NULLPTR_DEREFERENCE
         switch (static_cast<value_t>(n->kind))
@@ -102,6 +302,12 @@ BasicJsonType materialize(const document_data& d, const node* n)
             case value_t::array:
             {
                 const bool object = n->kind == node_kind::object;
+#if JSON_DIAGNOSTIC_POSITIONS
+                // (moved containers are also new)
+                const std::size_t start = (n->flags & node_flags::is_new) == 0 && n->off < d.size ? std::size_t{n->off} :
+                                          std::string::npos;
+                positions.set(start, start + 1);
+#endif
                 if (object)
                 {
                     sax.start_object(n->len);
@@ -118,8 +324,14 @@ BasicJsonType materialize(const document_data& d, const node* n)
                     open = deep.data();
                     capacity = deep.size();
                 }
+#if JSON_DIAGNOSTIC_POSITIONS
+                // (until an element is read, the container's own bracket is the last thing read)
+                open[depth++] = frame{nav::first(d, n), nav::end(d, n), object, start, positions.end};
+                break;
+#else
                 open[depth++] = frame {nav::first(d, n), nav::end(d, n), object};
                 break;
+#endif
             }
             case value_t::string:
             {
@@ -159,6 +371,15 @@ BasicJsonType materialize(const document_data& d, const node* n)
             frame& f = open[depth - 1];
             if (f.pos == f.end)
             {
+#if JSON_DIAGNOSTIC_POSITIONS
+                const std::size_t end = f.start == std::string::npos || f.last_end == std::string::npos ? std::string::npos : position_source::container_end(d.base[0], d.size, f.last_end);
+                // (an end of npos clears the start, see diagnostic_positions)
+                positions.set(end == std::string::npos ? end : end - 1, end);
+                if (depth > 1)
+                {
+                    open[depth - 2].last_end = end;
+                }
+#endif
                 if (f.object)
                 {
                     sax.end_object();

include/nlohmann/detail/view/node.hpp

@@ -69,7 +69,7 @@ struct node
     std::uint16_t extra; ///< numbers: integer digits (low byte) and fraction digits (high byte), 255 = "many"; objects: number of the object's key hash index (1-based, 0 = none); otherwise 0
     std::uint32_t off;   ///< source offset (string content, number token, literal, bracket); arena offset if escaped/edited; number of the element sequence if moved
     std::uint32_t len;   ///< string: decoded bytes; float: token bytes; array/object: element count
-    std::uint32_t next;  ///< array/object: number of nodes of the subtree (its extent in the enclosing sequence)
+    std::uint32_t next;  ///< array/object: number of nodes of the subtree (its extent in the enclosing sequence); escaped string: source offset of the opening quote plus one (JSON_DIAGNOSTIC_POSITIONS; 0: unknown)
 };
 static_assert(sizeof(node) == 16, "node must stay 16 bytes");
 

include/nlohmann/json.hpp

@@ -159,7 +159,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     friend class ::nlohmann::detail::binary_writer;
     template<typename BasicJsonType, typename InputType, typename SAX>
     friend class ::nlohmann::detail::binary_reader;
-    template<typename BasicJsonType, typename InputAdapterType, bool Collect>
+    template<typename BasicJsonType, typename InputAdapterType, bool Collect, typename LexerType>
     friend class ::nlohmann::detail::json_sax_dom_parser;
     template<typename BasicJsonType, typename InputAdapterType>
     friend class ::nlohmann::detail::json_sax_dom_binary_parser;

single_include/nlohmann/json.hpp

@@ -15629,7 +15629,10 @@ struct diagnostic_positions
         {
             // Lexer has read the first character of the container, so
             // subtract 1 from the position to get the correct start position.
-            v.start_position = lexer->get_chars_read_total() - 1;
+            // (npos: a value without a source position, see materialize() of
+            // json_view)
+            const std::size_t read = lexer->get_chars_read_total();
+            v.start_position = read == std::string::npos ? read : read - 1;
         }
     }
 
@@ -15644,6 +15647,12 @@ struct diagnostic_positions
         {
             // Lexer's position is past the closing brace or bracket, so set that as the end position.
             v.end_position = lexer->get_chars_read_total();
+            if (v.end_position == std::string::npos)
+            {
+                // a range has both ends or none (exception::diagnostics()
+                // prints only complete ones)
+                v.start_position = v.end_position;
+            }
         }
     }
 
@@ -15660,6 +15669,12 @@ struct diagnostic_positions
             // The start position will be set below based on the length of the string representation
             // of the value.
             v.end_position = lexer->get_chars_read_total();
+            if (v.end_position == std::string::npos)
+            {
+                // a value without a source position
+                v.start_position = v.end_position;
+                return;
+            }
 
             switch (v.type())
             {
@@ -15872,8 +15887,12 @@ read up to it.
 @tparam Collect  whether to collect the values of containers of unknown size on
                  a stack (only for a caller that does not use the value after a
                  parse error)
+@tparam LexerType  the type of the lexer that reports the source positions
+                   (JSON_DIAGNOSTIC_POSITIONS); only diagnostic_positions uses
+                   it, so any type with its three functions works (as
+                   materialize() of json_view uses it)
 */
-template<typename BasicJsonType, typename InputAdapterType, bool Collect = false>
+template<typename BasicJsonType, typename InputAdapterType, bool Collect = false, typename LexerType = lexer<BasicJsonType, InputAdapterType>>
 class json_sax_dom_parser : public json_sax_dom_error_state
 {
   public:
@@ -15882,7 +15901,7 @@ class json_sax_dom_parser : public json_sax_dom_error_state
     using number_float_t = typename BasicJsonType::number_float_t;
     using string_t = typename BasicJsonType::string_t;
     using binary_t = typename BasicJsonType::binary_t;
-    using lexer_t = lexer<BasicJsonType, InputAdapterType>;
+    using lexer_t = LexerType;
 
     /*!
     @param[in,out] r  reference to a JSON value that is manipulated while
@@ -22515,8 +22534,8 @@ using parser_callback_t =
 template<typename SAX>
 struct sax_ignores_number_text : std::false_type {};
 
-template<typename BasicJsonType, typename InputAdapterType, bool Collect>
-struct sax_ignores_number_text<json_sax_dom_parser<BasicJsonType, InputAdapterType, Collect>> : std::true_type {};
+template<typename BasicJsonType, typename InputAdapterType, bool Collect, typename LexerType>
+struct sax_ignores_number_text<json_sax_dom_parser<BasicJsonType, InputAdapterType, Collect, LexerType>> : std::true_type {};
 
 template<typename BasicJsonType, typename InputAdapterType>
 struct sax_ignores_number_text<json_sax_dom_callback_parser<BasicJsonType, InputAdapterType>> : std::true_type {};
@@ -24064,7 +24083,7 @@ NLOHMANN_JSON_NAMESPACE_END
 
 
 
-#include <algorithm> // copy
+#include <algorithm> // all_of, copy
 #include <array> // array
 #include <cctype> // isdigit
 #include <cerrno> // errno, ERANGE
@@ -24072,11 +24091,9 @@ NLOHMANN_JSON_NAMESPACE_END
 #include <cstdint> // uint64_t
 #include <cstdlib> // strtoull
 #include <cstring> // memchr, memcmp, memcpy
-#include <functional> // less
 #ifndef JSON_NO_IO
     #include <iosfwd> // ostream
 #endif  // JSON_NO_IO
-#include <iterator> // next
 #include <limits> // max
 #include <string> // string
 #include <utility> // move
@@ -24090,8 +24107,6 @@ NLOHMANN_JSON_NAMESPACE_END
 
 // #include <nlohmann/detail/meta/type_traits.hpp>
 
-// #include <nlohmann/detail/meta/void_t.hpp>
-
 // #include <nlohmann/detail/string_concat.hpp>
 
 // #include <nlohmann/detail/string_escape.hpp>
@@ -24202,26 +24217,6 @@ JSON_HEDLEY_ALWAYS_INLINE array_index_status parse_array_index(const StringType&
     return array_index_status::ok;
 }
 
-/// whether two keys of type @a StringType are equivalent under @a Compare
-/// exactly if they are equal: std::less<StringType> and std::less<>
-template<typename Compare, typename StringType>
-struct is_less_comparator : std::false_type {};
-
-template<typename StringType>
-struct is_less_comparator<std::less<StringType>, StringType> : std::true_type {};
-
-template<typename StringType>
-struct is_less_comparator<std::less<void>, StringType> : std::true_type {};
-
-/// whether the objects of type @a ObjectType find a key of type @a StringType
-/// exactly if it equals a stored key
-template<typename ObjectType, typename StringType, typename = void>
-struct finds_equal_keys : std::false_type {};
-
-template<typename ObjectType, typename StringType>
-struct finds_equal_keys<ObjectType, StringType, void_t<typename ObjectType::key_compare, typename ObjectType::key_type>>
-    : conjunction<is_less_comparator<typename ObjectType::key_compare, StringType>, std::is_same<typename ObjectType::key_type, StringType>> {};
-
 }  // namespace detail
 
 /// @brief JSON Pointer defines a string syntax for identifying a specific value within a JSON document
@@ -24677,225 +24672,6 @@ class json_pointer
         return object_member_impl(object, key, detail::priority_tag<1> {});
     }
 
-    /// @brief append a null value to @a array, like operator[] with the size of @a array
-    template<typename BasicJsonType>
-    static BasicJsonType& array_append(BasicJsonType& array)
-    {
-        auto& elements = *array.m_data.m_value.array;
-        const auto old_capacity = array.container_capacity();
-        elements.emplace_back();
-        return array.set_parent_after_insert(elements.back(), old_capacity);
-    }
-
-    /// @brief add @a key, which is missing, to @a object
-    template<typename BasicJsonType>
-    static auto object_add_impl(BasicJsonType& object, const string_t& key, detail::priority_tag<1> /*unused*/)
-    -> decltype(object.m_data.m_value.object->emplace(key, nullptr), std::declval<BasicJsonType&>())
-    {
-        const auto old_capacity = object.container_capacity();
-        const auto it = object.m_data.m_value.object->emplace(key, nullptr).first;
-        return object.set_parent_after_insert(it->second, old_capacity);
-    }
-
-    template<typename BasicJsonType>
-    static BasicJsonType& object_add_impl(BasicJsonType& object, const string_t& key, detail::priority_tag<0> /*unused*/)
-    {
-        return object.operator[](key);
-    }
-
-    template<typename BasicJsonType>
-    static BasicJsonType& object_add(BasicJsonType& object, const string_t& key)
-    {
-        return object_add_impl(object, key, detail::priority_tag<1> {});
-    }
-
-    /// @brief search @a key in @a members: the result is where the key is or,
-    /// for objects that can insert at a position (std::map), where it belongs
-    template<typename ObjectType>
-    static auto object_search_impl(ObjectType& members, const string_t& key, detail::priority_tag<1> /*unused*/)
-    -> decltype(members.key_comp()(key, members.lower_bound(key)->first), members.lower_bound(key))
-    {
-        return members.lower_bound(key);
-    }
-
-    template<typename ObjectType>
-    static auto object_search_impl(ObjectType& members, const string_t& key, detail::priority_tag<0> /*unused*/)
-    -> decltype(members.find(key))
-    {
-        return members.find(key);
-    }
-
-    template<typename ObjectType>
-    static auto object_search(ObjectType& members, const string_t& key)
-    -> decltype(object_search_impl(members, key, detail::priority_tag<1> {}))
-    {
-        return object_search_impl(members, key, detail::priority_tag<1> {});
-    }
-
-    /// @brief whether @a it, the result of @ref object_search for @a key, points to @a key
-    ///
-    /// With std::less, the key at the lower bound is equivalent to @a key
-    /// exactly if it is equal to it, and comparing for equality is cheaper.
-    template<typename ObjectType, typename Iterator,
-             detail::enable_if_t<detail::finds_equal_keys<ObjectType, string_t>::value, int> = 0>
-    static auto object_search_found_impl(ObjectType& members, const Iterator& it, const string_t& key, detail::priority_tag<2> /*unused*/)
-    -> decltype(members.lower_bound(key), it->first == key)
-    {
-        return it != members.end() && it->first == key;
-    }
-
-    template<typename ObjectType, typename Iterator>
-    static auto object_search_found_impl(ObjectType& members, const Iterator& it, const string_t& key, detail::priority_tag<1> /*unused*/)
-    -> decltype(members.key_comp()(key, it->first), members.lower_bound(key), bool())
-    {
-        return it != members.end() && !members.key_comp()(key, it->first);
-    }
-
-    template<typename ObjectType, typename Iterator>
-    static bool object_search_found_impl(ObjectType& members, const Iterator& it, const string_t& /*key*/, detail::priority_tag<0> /*unused*/)
-    {
-        return it != members.end();
-    }
-
-    template<typename ObjectType, typename Iterator>
-    static bool object_search_found(ObjectType& members, const Iterator& it, const string_t& key)
-    {
-        return object_search_found_impl(members, it, key, detail::priority_tag<2> {});
-    }
-
-    /// @brief insert @a key, which is missing, into @a object at @a it, the
-    /// result of @ref object_search for @a key
-    template<typename BasicJsonType, typename Iterator>
-    static auto object_insert_impl(BasicJsonType& object, const Iterator& it, const string_t& key, detail::priority_tag<1> /*unused*/)
-    -> decltype(object.m_data.m_value.object->emplace_hint(it, key, nullptr), std::declval<BasicJsonType&>())
-    {
-        const auto old_capacity = object.container_capacity();
-        const auto pos = object.m_data.m_value.object->emplace_hint(it, key, nullptr);
-        return object.set_parent_after_insert(pos->second, old_capacity);
-    }
-
-    template<typename BasicJsonType, typename Iterator>
-    static BasicJsonType& object_insert_impl(BasicJsonType& object, const Iterator& /*it*/, const string_t& key, detail::priority_tag<0> /*unused*/)
-    {
-        return object_add(object, key);
-    }
-
-    template<typename BasicJsonType, typename Iterator>
-    static BasicJsonType& object_insert(BasicJsonType& object, const Iterator& it, const string_t& key)
-    {
-        return object_insert_impl(object, it, key, detail::priority_tag<1> {});
-    }
-
-    /*!
-    @brief undoes the change @ref get_unchecked_create made to an existing value
-
-    @ref get_unchecked walks existing values without changing them. At the
-    first reference token that does not select an existing value, @ref
-    get_unchecked_create makes exactly one change to an existing value: it
-    converts a null value, inserts a key into an object, or grows an array.
-    Everything it creates afterwards lies below that change. If a later step
-    throws, the destructor of this guard reverts that one change, which
-    removes everything created after it, so the value is left as it was
-    (strong exception safety). The guard needs no try/catch and therefore also
-    compiles with JSON_NOEXCEPTION.
-
-    Reverting the change must not throw, as it happens in a destructor. It
-    erases the inserted member by its iterator (no key is converted or
-    compared, nothing is allocated), erases the added elements at the end of
-    the array, or swaps the null value back. This holds for std::map,
-    std::vector, ordered_map, and every object_t, array_t, and
-    json_base_class_t whose erase() and move operations do not throw.
-    Between recording and reverting, nothing is inserted into or erased from
-    the object or array, so the iterator stays valid.
-    */
-    template<typename BasicJsonType>
-    class get_unchecked_rollback
-    {
-      public:
-        using object_iterator = typename BasicJsonType::object_t::iterator;
-
-        /// record that @a member was inserted into the object @a value
-        get_unchecked_rollback(BasicJsonType* value, const object_iterator& member)
-            : m_value(value)
-            , m_member(member)
-            , m_change(change::key_inserted)
-        {}
-
-        /// record the change that the next reference token makes to the null value or array @a value
-        explicit get_unchecked_rollback(BasicJsonType* value)
-            : m_value(value)
-        {
-            if (value->is_null())
-            {
-                // keep the null value (with its base class and positions) and
-                // continue with a fresh null value in its place, which is what
-                // assigning an array or object to it would have left there
-                m_saved_null.swap(*value);
-                m_change = change::null_converted;
-            }
-            else
-            {
-                JSON_ASSERT(value->is_array());
-                m_old_size = value->m_data.m_value.array->size();
-                m_change = change::array_grown;
-            }
-        }
-
-        get_unchecked_rollback(const get_unchecked_rollback&) = delete;
-        get_unchecked_rollback(get_unchecked_rollback&&) = delete;
-        get_unchecked_rollback& operator=(const get_unchecked_rollback&) = delete;
-        get_unchecked_rollback& operator=(get_unchecked_rollback&&) = delete;
-
-        ~get_unchecked_rollback()
-        {
-            undo();
-        }
-
-        /// keep the change
-        void commit() noexcept
-        {
-            m_change = change::none;
-        }
-
-      private:
-        void undo() noexcept
-        {
-            switch (m_change)
-            {
-                case change::null_converted:
-                    // the values created since go away with m_saved_null
-                    m_value->swap(m_saved_null);
-                    break;
-                case change::key_inserted:
-                    m_value->m_data.m_value.object->erase(m_member);
-                    break;
-                case change::array_grown:
-                {
-                    auto& elements = *m_value->m_data.m_value.array;
-                    elements.resize(m_old_size);
-                    break;
-                }
-                case change::none:
-                default:
-                    break;
-            }
-        }
-
-        enum class change
-        {
-            none,
-            null_converted,
-            key_inserted,
-            array_grown
-        };
-
-        BasicJsonType* m_value;
-        object_iterator m_member {};
-        typename BasicJsonType::size_type m_old_size = 0;
-        change m_change = change::none;
-        BasicJsonType m_saved_null {};
-    };
-
   JSON_PRIVATE_UNLESS_TESTED:
     json_pointer top() const
     {
@@ -25279,245 +25055,47 @@ class json_pointer
 
     Complexity: Linear in the length of the JSON pointer.
 
-    Exception safety: Strong guarantee. This function walks existing values
-    until the first reference token that does not select one. If that is the
-    last reference token, inserting the key into the object or growing the
-    array is strongly exception safe by itself; any other change is made by
-    @ref get_unchecked_create, which undoes it if a later step throws.
-
-    @throw parse_error.106   if an array index of an existing array begins with '0'
-    @throw parse_error.109   if an array index of an existing array was not a number
-    @throw out_of_range.404  if the JSON pointer can not be resolved, or if an
-                             array index is too large for strtoull
-    @throw out_of_range.410  if an array index exceeds size_type
-    @throw std::length_error if padding an array exceeds its maximal size
-    @throw std::bad_alloc    if an allocation fails
+    @throw parse_error.106   if an array index begins with '0'
+    @throw parse_error.109   if an array index was not a number
+    @throw out_of_range.404  if the JSON pointer can not be resolved
     */
     template<typename BasicJsonType>
     BasicJsonType& get_unchecked(BasicJsonType* ptr) const
     {
-        const auto* token = reference_tokens.data();
-        const auto* const end = token + reference_tokens.size();
-        if (token == end)
+        for (const auto& reference_token : reference_tokens)
         {
-            return *ptr;
-        }
-        if (ptr->is_null())
-        {
-            // the null value is converted to an array or an object
-            return get_unchecked_create(ptr, token, end);
-        }
-
-        // walk existing values; the walk itself inserts nothing, which keeps
-        // the loop fast (insertions are done below or in get_unchecked_create)
-        typename BasicJsonType::object_t::iterator it;
-        do
-        {
-            if (ptr->is_object())
-            {
-                auto& members = *ptr->m_data.m_value.object;
-                it = object_search(members, *token);
-                if (!object_search_found(members, it, *token))
-                {
-                    // the key is inserted below or in get_unchecked_create
-                    break;
-                }
-                ptr = &it->second;
-            }
-            else if (ptr->is_array())
-            {
-                if (is_dash(*token))
-                {
-                    if (token + 1 == end)
-                    {
-                        // explicitly treat "-" as index beyond the end
-                        return array_append(*ptr);
-                    }
-                    // an element will be appended in get_unchecked_create
-                    break;
-                }
-                if (token + 1 == end)
-                {
-                    // convert array index to number; unchecked access
-                    return ptr->operator[](array_index<BasicJsonType>(*token));
-                }
-                const auto idx = array_index<BasicJsonType>(*token);
-                if (idx >= ptr->m_data.m_value.array->size())
-                {
-                    // the array will be padded in get_unchecked_create
-                    break;
-                }
-                ptr = &(*ptr->m_data.m_value.array)[idx];
-            }
-            else if (ptr->is_null())
-            {
-                // the null value will be converted in get_unchecked_create
-                break;
-            }
-            else
-            {
-                // primitive value with a reference token left
-                throw_unresolved(*token, ptr);
-            }
-        }
-        while (++token != end);
-
-        if (token == end)
-        {
-            return *ptr;
-        }
-        if (token + 1 == end && ptr->is_object())
-        {
-            // insert the missing key where the walk found it belongs
-            return object_insert(*ptr, it, *token);
-        }
-        return get_unchecked_create(ptr, token, end);
-    }
-
-    /*!
-    @brief create the values for the reference tokens from @a first on
-
-    Continues @ref get_unchecked at the first reference token that does not
-    select an existing value. That token changes @a ptr, an existing value (see
-    @ref get_unchecked_rollback); all later tokens only change values created
-    here.
-
-    If the emplace() of the object type finds a member that the lookup in @ref
-    get_unchecked did not find (the two disagree, e.g. for fifo_map), nothing
-    is inserted, and the walk continues with that member as in @ref
-    get_unchecked, which is what basic_json::operator[] does.
-
-    @param[in] ptr    the value the reference token @a first is applied to
-    @param[in] first  the first reference token to resolve (an element of
-                      @ref reference_tokens)
-    @param[in] end    the end of @ref reference_tokens
-
-    @throw parse_error.106   if an array index of an existing array begins with
-                             '0' (only after emplace() found a member, see above)
-    @throw parse_error.109   if an array index of an existing array was not a
-                             number (only after emplace() found a member)
-    @throw out_of_range.404  if an array index is too large for strtoull, or (only
-                             after emplace() found a member) if the JSON pointer
-                             can not be resolved
-    @throw out_of_range.410  if an array index exceeds size_type
-    @throw std::length_error if padding an array exceeds its maximal size
-    @throw std::bad_alloc    if an allocation fails
-    */
-    template<typename BasicJsonType>
-    JSON_HEDLEY_NEVER_INLINE static BasicJsonType& get_unchecked_create(BasicJsonType* ptr, const string_t* first, const string_t* end)
-    {
-        const auto* token = first;
-        while (ptr->is_object())
-        {
-            const auto old_capacity = ptr->container_capacity();
-            const auto inserted = ptr->m_data.m_value.object->emplace(*token, nullptr);
-            if (JSON_HEDLEY_LIKELY(inserted.second))
-            {
-                get_unchecked_rollback<BasicJsonType> rollback(ptr, inserted.first);
-                BasicJsonType& result = create_values(&ptr->set_parent_after_insert(inserted.first->second, old_capacity), token + 1, end);
-                rollback.commit();
-                return result;
-            }
-
-            // nothing was inserted: walk existing values from the member
-            // emplace() found on, like get_unchecked
-            ptr = &inserted.first->second;
-            while (++token != end)
-            {
-                if (ptr->is_object())
-                {
-                    auto& members = *ptr->m_data.m_value.object;
-                    const auto it = object_search(members, *token);
-                    if (!object_search_found(members, it, *token))
-                    {
-                        break;
-                    }
-                    ptr = &it->second;
-                }
-                else if (ptr->is_array())
-                {
-                    if (is_dash(*token))
-                    {
-                        break;
-                    }
-                    const auto idx = array_index<BasicJsonType>(*token);
-                    if (idx >= ptr->m_data.m_value.array->size())
-                    {
-                        break;
-                    }
-                    ptr = &(*ptr->m_data.m_value.array)[idx];
-                }
-                else if (ptr->is_null())
-                {
-                    break;
-                }
-                else
-                {
-                    // primitive value with a reference token left
-                    throw_unresolved(*token, ptr);
-                }
-            }
-            if (token == end)
-            {
-                return *ptr;
-            }
-        }
-
-        get_unchecked_rollback<BasicJsonType> rollback(ptr);
-        BasicJsonType& result = create_values(ptr, token, end);
-        rollback.commit();
-        return result;
-    }
-
-    /*!
-    @brief the loop of @ref get_unchecked_create
-
-    @a ptr is a null value or an array. Every value created here is a fresh
-    one, so every object a key is added to is empty.
-
-    @throw out_of_range.404  if an array index is too large for strtoull
-    @throw out_of_range.410  if an array index exceeds size_type
-    @throw std::length_error if padding an array exceeds its maximal size
-    @throw std::bad_alloc    if an allocation fails
-    */
-    template<typename BasicJsonType>
-    static BasicJsonType& create_values(BasicJsonType* ptr, const string_t* first, const string_t* end)
-    {
-        for (const auto* token = first; token != end; ++token)
-        {
-            const auto& reference_token = *token;
-
             // convert null values to arrays or objects before continuing
             if (ptr->is_null())
             {
-                // change value to an array for array indices or "-" or to an
-                // object otherwise; every null value here is a fresh one (see
-                // get_unchecked_rollback), so converting it in place leaves
-                // the same value as assigning an array or object to it
-                if (is_array_index_token(reference_token) || is_dash(reference_token))
+                // check if the reference token is a valid array index, that is
+                // a nonempty sequence of digits without a leading '0'
+                // (cf. RFC 6901, Sect. 4); tokens that could never be a valid
+                // array index (such as "01" or "") are treated as object keys
+                const bool nums = !reference_token.empty()
+                                  && (reference_token.size() == 1 || reference_token[0] != '0')
+                                  && std::all_of(reference_token.begin(), reference_token.end(),
+                                                 [](const unsigned char x)
                 {
-                    ptr->template convert_null_to<typename BasicJsonType::array_t>();
-                }
-                else
-                {
-                    ptr->template convert_null_to<typename BasicJsonType::object_t>();
-                }
+                    return std::isdigit(x);
+                });
+
+                // change value to an array for array indices or "-" or to object otherwise
+                *ptr = (nums || reference_token == "-")
+                       ? detail::value_t::array
+                       : detail::value_t::object;
             }
 
             if (ptr->is_object())
             {
-                // the object is new and empty
-                ptr = &object_add(*ptr, reference_token);
+                // use unchecked object access
+                ptr = &object_member(*ptr, reference_token);
             }
-            else
+            else if (ptr->is_array())
             {
-                // only the first value is not created here, and it is a null
-                // value or an array (see get_unchecked_create)
-                JSON_ASSERT(ptr->is_array());
-                if (is_dash(reference_token))
+                if (reference_token == "-")
                 {
                     // explicitly treat "-" as index beyond the end
-                    ptr = &array_append(*ptr);
+                    ptr = &ptr->operator[](ptr->m_data.m_value.array->size());
                 }
                 else
                 {
@@ -25525,31 +25103,16 @@ class json_pointer
                     ptr = &ptr->operator[](array_index<BasicJsonType>(reference_token));
                 }
             }
+            else
+            {
+                // primitive value with a reference token left
+                throw_unresolved(reference_token, ptr);
+            }
         }
 
         return *ptr;
     }
 
-    /// whether @a s is a valid array index, that is a nonempty sequence of
-    /// digits without a leading '0' (cf. RFC 6901, Sect. 4); tokens that could
-    /// never be a valid array index (such as "01" or "") are object keys
-    static bool is_array_index_token(const string_t& s)
-    {
-        const std::size_t size = s.size();
-        if (size == 0 || (size > 1 && s[0] == '0'))
-        {
-            return false;
-        }
-        for (std::size_t i = 0; i < size; ++i)
-        {
-            if (std::isdigit(static_cast<unsigned char>(s[i])) == 0)
-            {
-                return false;
-            }
-        }
-        return true;
-    }
-
     /*!
     @throw parse_error.106   if an array index begins with '0'
     @throw parse_error.109   if an array index was not a number
@@ -36910,7 +36473,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     friend class ::nlohmann::detail::binary_writer;
     template<typename BasicJsonType, typename InputType, typename SAX>
     friend class ::nlohmann::detail::binary_reader;
-    template<typename BasicJsonType, typename InputAdapterType, bool Collect>
+    template<typename BasicJsonType, typename InputAdapterType, bool Collect, typename LexerType>
     friend class ::nlohmann::detail::json_sax_dom_parser;
     template<typename BasicJsonType, typename InputAdapterType>
     friend class ::nlohmann::detail::json_sax_dom_binary_parser;

single_include/nlohmann/json_view.hpp

@@ -269,7 +269,7 @@ struct node
     std::uint16_t extra; ///< numbers: integer digits (low byte) and fraction digits (high byte), 255 = "many"; objects: number of the object's key hash index (1-based, 0 = none); otherwise 0
     std::uint32_t off;   ///< source offset (string content, number token, literal, bracket); arena offset if escaped/edited; number of the element sequence if moved
     std::uint32_t len;   ///< string: decoded bytes; float: token bytes; array/object: element count
-    std::uint32_t next;  ///< array/object: number of nodes of the subtree (its extent in the enclosing sequence)
+    std::uint32_t next;  ///< array/object: number of nodes of the subtree (its extent in the enclosing sequence); escaped string: source offset of the opening quote plus one (JSON_DIAGNOSTIC_POSITIONS; 0: unknown)
 };
 static_assert(sizeof(node) == 16, "node must stay 16 bytes");
 
@@ -2402,7 +2402,13 @@ indent_done:
                 return false;
             }
             p = r.p;
+#if JSON_DIAGNOSTIC_POSITIONS
+            // the decoded string is in the arena: next keeps the source offset
+            // of the opening quote plus one (0: unknown) for materialize()
+            push_node(node_kind::string, node_flags::escaped, 0, r.start, static_cast<std::uint64_t>(r.len) | (static_cast<std::uint64_t>(s - b) << 32));
+#else
             push_node(node_kind::string, node_flags::escaped, 0, r.start, r.len);
+#endif
             return true;
         }
     };
@@ -4943,7 +4949,8 @@ constexpr std::uint64_t image_limit = 0xFFFFFFF0u;
 /// Copy the current structure of an edited document into nodes in document
 /// order, as the parser would have written them. Text written by edits is
 /// appended to text_tail (number tokens) and arena_tail (strings); floats that
-/// are not finite become null, as dump() writes them.
+/// are not finite become null, as dump() writes them. Nodes keep the flag
+/// is_new: they have no source position (JSON_DIAGNOSTIC_POSITIONS).
 inline void compact_nodes(const document_data& d, std::size_t arena_size, std::vector<node>& out, std::string& text_tail, std::string& arena_tail)
 {
     struct frame
@@ -4966,16 +4973,18 @@ inline void compact_nodes(const document_data& d, std::size_t arena_size, std::v
             arena_tail.append(d.str(s), s.len);
             r.flags = node_flags::escaped;
         }
+        r.flags = static_cast<std::uint8_t>(r.flags | (s.flags & node_flags::is_new));
         return r;
     };
     const auto copy_node = [&](const node * v)
     {
         node r = *v;
+        const auto is_new = static_cast<std::uint8_t>(v->flags & node_flags::is_new);
         switch (static_cast<value_t>(v->kind))
         {
             case value_t::object:
             case value_t::array:
-                r.flags = 0;
+                r.flags = is_new;
                 r.extra = 0;
                 r.off = (v->flags & (node_flags::moved | node_flags::is_new)) != 0 ? 0 : v->off;
                 r.len = 0;  // counted below
@@ -4992,7 +5001,7 @@ inline void compact_nodes(const document_data& d, std::size_t arena_size, std::v
                     r.off = static_cast<std::uint32_t>(d.size + text_tail.size());
                     text_tail.append(d.str(*v), number_length(*v));
                 }
-                r.flags = 0;
+                r.flags = is_new;
                 break;
             case value_t::number_float:
                 if ((v->flags & node_flags::storage) == node_flags::edited)
@@ -5002,22 +5011,23 @@ inline void compact_nodes(const document_data& d, std::size_t arena_size, std::v
                     {
                         r = node{}; // nan and infinity: null, as dump() writes them
                         r.kind = node_kind::null;
+                        r.flags = is_new;
                         break;
                     }
                     r.off = static_cast<std::uint32_t>(d.size + text_tail.size());
                     text_tail.append(t, v->len);
                     r.extra = 0xFFFFu; // the digit layout is not recorded
                 }
-                r.flags = 0;
+                r.flags = is_new;
                 break;
             case value_t::boolean:
-                r.flags = static_cast<std::uint8_t>(v->flags & node_flags::is_true);
+                r.flags = static_cast<std::uint8_t>(v->flags & (node_flags::is_true | node_flags::is_new));
                 break;
             case value_t::null:
             case value_t::binary:
             case value_t::discarded:
             default:
-                r.flags = 0;
+                r.flags = is_new;
                 break;
         }
         out.push_back(r);
@@ -5378,13 +5388,15 @@ inline bool check_image(const node* nodes, std::size_t count, const unsigned cha
     std::vector<float_range> floats;
     const auto check_string = [&](const node & n) -> bool
     {
-        if ((n.flags & ~node_flags::escaped) != 0 || n.extra != 0)
+        if ((n.flags & ~(node_flags::escaped | node_flags::is_new)) != 0 || n.extra != 0)
         {
             return false;
         }
         const bool decoded = (n.flags & node_flags::escaped) != 0;
         const std::size_t limit = decoded ? arena_size : text_size;
-        if (n.off > limit || n.len > limit - n.off)
+        // (next: the source offset of a decoded string's opening quote plus
+        // one, or 0; see node)
+        if (n.off > limit || n.len > limit - n.off || n.next > text_size)
         {
             return false;
         }
@@ -5456,13 +5468,13 @@ inline bool check_image(const node* nodes, std::size_t count, const unsigned cha
         {
             case value_t::null:
                 // (the offset of a literal is read to size the output of dump())
-                if (n.flags != 0 || n.extra != 0 || n.off > text_size)
+                if ((n.flags & ~node_flags::is_new) != 0 || n.extra != 0 || n.off > text_size)
                 {
                     return false;
                 }
                 break;
             case value_t::boolean:
-                if ((n.flags & ~node_flags::is_true) != 0 || n.extra != 0 || n.off > text_size)
+                if ((n.flags & ~(node_flags::is_true | node_flags::is_new)) != 0 || n.extra != 0 || n.off > text_size)
                 {
                     return false;
                 }
@@ -5476,7 +5488,7 @@ inline bool check_image(const node* nodes, std::size_t count, const unsigned cha
             case value_t::number_integer:
             case value_t::number_unsigned:
             case value_t::number_float:
-                if (n.flags != 0 || !number_in_bounds(n))
+                if ((n.flags & ~node_flags::is_new) != 0 || !number_in_bounds(n))
                 {
                     return false;
                 }
@@ -5498,7 +5510,7 @@ inline bool check_image(const node* nodes, std::size_t count, const unsigned cha
             case value_t::object:
             {
                 const std::size_t limit = stack.empty() ? count : stack.back().end;
-                if (n.flags != 0 || n.extra != 0 || n.next == 0 || n.next > limit - i || n.off > text_size)
+                if ((n.flags & ~node_flags::is_new) != 0 || n.extra != 0 || n.next == 0 || n.next > limit - i || n.off > text_size)
                 {
                     return false;
                 }
@@ -6108,6 +6120,176 @@ namespace detail
 namespace view
 {
 
+#if JSON_DIAGNOSTIC_POSITIONS
+/*!
+@brief the source positions of the values materialize() replays
+
+Stands in for the lexer of json_sax_dom_parser, which reads the positions of
+the values it stores from these three functions (diagnostic_positions). npos
+is a value without a source position.
+*/
+struct position_source
+{
+    /// the token, of which diagnostic_positions only reads the length
+    struct token
+    {
+        std::size_t length;
+        std::size_t size() const noexcept
+        {
+            return length;
+        }
+    };
+
+    std::size_t start = std::string::npos; ///< the first byte of the next value
+    std::size_t end = std::string::npos;   ///< one past the next value (start_object/start_array: one past the bracket)
+
+    std::size_t get_chars_read_total() const noexcept
+    {
+        return end;
+    }
+    std::size_t get_token_start_position() const noexcept
+    {
+        return start;
+    }
+    token get_string() const noexcept
+    {
+        return token{end - start};
+    }
+
+    /// the range [first, last), or none if either is npos
+    void set(std::size_t first, std::size_t last) noexcept
+    {
+        const bool known = first != std::string::npos && last != std::string::npos;
+        start = known ? first : std::string::npos;
+        end = known ? last : std::string::npos;
+    }
+
+    /// one past the closing quote of the string whose opening quote is at
+    /// src[quote], or npos (the scan is bounded by size, as images can be
+    /// loaded without a check)
+    static std::size_t string_end(const char* src, std::size_t size, std::size_t quote) noexcept
+    {
+        for (std::size_t i = quote + 1; i < size; ++i)
+        {
+            if (src[i] == '\\')
+            {
+                ++i;
+            }
+            else if (src[i] == '"')
+            {
+                return i + 1;
+            }
+        }
+        return std::string::npos;
+    }
+
+    /// one past the closing bracket of the array or object whose last element
+    /// ends at src[pos] (or whose opening bracket is at src[pos - 1]), or npos;
+    /// in between, there can only be whitespace, comments, and a trailing comma
+    /// (the source was validated when it was parsed)
+    static std::size_t container_end(const char* src, std::size_t size, std::size_t pos) noexcept
+    {
+        while (pos < size)
+        {
+            switch (src[pos])
+            {
+                case ' ':
+                case '\t':
+                case '\n':
+                case '\r':
+                case ',':
+                    ++pos;
+                    break;
+                case ']':
+                case '}':
+                    return pos + 1;
+                case '/':
+                    if (pos + 1 < size && src[pos + 1] == '/')
+                    {
+                        pos += 2;
+                        while (pos < size && src[pos] != '\n' && src[pos] != '\r')
+                        {
+                            ++pos;
+                        }
+                        break;
+                    }
+                    if (pos + 1 < size && src[pos + 1] == '*')
+                    {
+                        pos += 2;
+                        while (pos < size && !(src[pos] == '*' && pos + 1 < size && src[pos + 1] == '/'))
+                        {
+                            ++pos;
+                        }
+                        pos += 2;
+                        break;
+                    }
+                    return std::string::npos;
+                default:
+                    return std::string::npos;
+            }
+        }
+        return std::string::npos;
+    }
+
+    /// the range of the scalar n of document d
+    void set_scalar(const document_data& d, const node& n) noexcept
+    {
+        const std::size_t size = d.size;
+        const std::size_t off = n.off;
+        std::size_t first = std::string::npos;
+        std::size_t last = std::string::npos;
+        if ((n.flags & node_flags::is_new) == 0)
+        {
+            switch (static_cast<value_t>(n.kind))
+            {
+                case value_t::string:
+                    if ((n.flags & node_flags::storage) == 0)
+                    {
+                        // off is the first byte after the opening quote
+                        if (off != 0)
+                        {
+                            first = off - 1;
+                            last = off + std::size_t{n.len} + 1;
+                        }
+                    }
+                    else if ((n.flags & node_flags::storage) == node_flags::escaped && n.next != 0)
+                    {
+                        // next is the offset of the opening quote plus one
+                        first = n.next - 1;
+                        last = string_end(d.base[0], size, first);
+                    }
+                    break;
+                case value_t::number_integer:
+                case value_t::number_unsigned:
+                case value_t::number_float:
+                    if ((n.flags & node_flags::storage) == 0)
+                    {
+                        first = off;
+                        last = off + number_length(n);
+                    }
+                    break;
+                case value_t::boolean:
+                    first = off;
+                    last = off + ((n.flags & node_flags::is_true) != 0 ? 4u : 5u);
+                    break;
+                case value_t::null:
+                    first = off;
+                    last = off + 4u;
+                    break;
+                case value_t::object:
+                case value_t::array:
+                case value_t::binary:
+                case value_t::discarded:
+                default:
+                    break;
+            }
+        }
+        // (a crafted image can point past the text)
+        set(first, last != std::string::npos && last <= size ? last : std::string::npos);
+    }
+};
+#endif
+
 /*!
 @brief the basic_json value of the subtree at n
 
@@ -6115,14 +6297,22 @@ The subtree is replayed into the SAX handler that parse() uses to build its
 values, so the result is the value parse() would produce: duplicate keys keep
 the last value, and with JSON_DIAGNOSTICS the parent pointers are set. It is
 iterative, so the nesting depth is limited by memory only, as for parse().
-Without a lexer the handler records no source positions
-(JSON_DIAGNOSTIC_POSITIONS).
+
+With JSON_DIAGNOSTIC_POSITIONS, the values get their source positions as with
+parse(): position_source stands in for the lexer. Values written by edits have
+none (npos), and neither has an array or object whose elements changed, or
+whose last element has none (the end of its closing bracket is found by
+scanning from the end of the last element).
 */
 template<typename BasicJsonType, bool Editable>
 BasicJsonType materialize(const document_data& d, const node* n)
 {
     using string_t = typename BasicJsonType::string_t;
+#if JSON_DIAGNOSTIC_POSITIONS
+    using sax_t = json_sax_dom_parser<BasicJsonType, iterator_input_adapter<const char*>, true, position_source>;
+#else
     using sax_t = json_sax_dom_parser<BasicJsonType, iterator_input_adapter<const char*>, true>;
+#endif
     using nav = navigation<Editable>;
 
     // the open containers: their next element (or key of the next member),
@@ -6134,9 +6324,15 @@ BasicJsonType materialize(const document_data& d, const node* n)
         const node* pos;
         const node* end;
         bool object;
+#if JSON_DIAGNOSTIC_POSITIONS
+        std::size_t start;    ///< the opening bracket (npos: unknown)
+        std::size_t last_end; ///< the end of the last element read (npos: unknown)
+#endif
     };
 
+#if !JSON_DIAGNOSTIC_POSITIONS
     // a scalar needs neither the handler nor the stack of open containers
+    // (with positions, it goes through the handler, which sets them)
     switch (static_cast<value_t>(n->kind))
     {
         case value_t::string:
@@ -6158,9 +6354,15 @@ BasicJsonType materialize(const document_data& d, const node* n)
         default:
             break;
     }
+#endif
 
     BasicJsonType result;
+#if JSON_DIAGNOSTIC_POSITIONS
+    position_source positions;
+    sax_t sax(result, true, &positions);
+#else
     sax_t sax(result, true);
+#endif
     const string_t no_token {};
     // (shallow subtrees on the stack: a call for a small value then allocates only for the value)
     std::array<frame, 16> shallow; // NOLINT(cppcoreguidelines-pro-type-member-init,hicpp-member-init): filled as containers open
@@ -6176,6 +6378,16 @@ BasicJsonType materialize(const document_data& d, const node* n)
     std::size_t depth = 0;
     for (;;)
     {
+#if JSON_DIAGNOSTIC_POSITIONS
+        if (!is_container(*n))
+        {
+            positions.set_scalar(d, *n);
+            if (depth != 0)
+            {
+                open[depth - 1].last_end = positions.end;
+            }
+        }
+#endif
         // false positive: n comes from nav::value(), which never returns null for a valid index
         // @infer-ignore NULLPTR_DEREFERENCE
         switch (static_cast<value_t>(n->kind))
@@ -6184,6 +6396,12 @@ BasicJsonType materialize(const document_data& d, const node* n)
             case value_t::array:
             {
                 const bool object = n->kind == node_kind::object;
+#if JSON_DIAGNOSTIC_POSITIONS
+                // (moved containers are also new)
+                const std::size_t start = (n->flags & node_flags::is_new) == 0 && n->off < d.size ? std::size_t{n->off} :
+                                          std::string::npos;
+                positions.set(start, start + 1);
+#endif
                 if (object)
                 {
                     sax.start_object(n->len);
@@ -6200,8 +6418,14 @@ BasicJsonType materialize(const document_data& d, const node* n)
                     open = deep.data();
                     capacity = deep.size();
                 }
+#if JSON_DIAGNOSTIC_POSITIONS
+                // (until an element is read, the container's own bracket is the last thing read)
+                open[depth++] = frame{nav::first(d, n), nav::end(d, n), object, start, positions.end};
+                break;
+#else
                 open[depth++] = frame {nav::first(d, n), nav::end(d, n), object};
                 break;
+#endif
             }
             case value_t::string:
             {
@@ -6241,6 +6465,15 @@ BasicJsonType materialize(const document_data& d, const node* n)
             frame& f = open[depth - 1];
             if (f.pos == f.end)
             {
+#if JSON_DIAGNOSTIC_POSITIONS
+                const std::size_t end = f.start == std::string::npos || f.last_end == std::string::npos ? std::string::npos : position_source::container_end(d.base[0], d.size, f.last_end);
+                // (an end of npos clears the start, see diagnostic_positions)
+                positions.set(end == std::string::npos ? end : end - 1, end);
+                if (depth > 1)
+                {
+                    open[depth - 2].last_end = end;
+                }
+#endif
                 if (f.object)
                 {
                     sax.end_object();

tests/src/unit-alt-string.cpp

@@ -373,23 +373,6 @@ TEST_CASE("alternative string type")
         CHECK_FALSE(j.contains(alt_json::json_pointer("/foo/bar")));
     }
 
-    SECTION("non-const operator[](json_pointer)")
-    {
-        // creating values must compile without string_t::begin()
-        alt_json j = alt_json::parse(R"({"a":{"b":[1]},"c":null})");
-        const alt_json before = j;
-        j[alt_json::json_pointer("/a/b/3/x/-/y")] = 1; // pad, append, create
-        j[alt_json::json_pointer("/a/z")] = 2;         // insert a key
-        j[alt_json::json_pointer("/c/0/q")] = 3;       // convert null
-        j[alt_json::json_pointer("/a/b/-")] = 4;       // append
-        CHECK(j.dump() == R"({"a":{"b":[1,null,null,{"x":[{"y":1}]},4],"z":2},"c":[{"q":3}]})");
-
-        // a failing access leaves the value unchanged
-        j = before;
-        CHECK_THROWS_AS(j[alt_json::json_pointer("/a/n/99999999999999999999999")], alt_json::out_of_range&);
-        CHECK(j == before);
-    }
-
     SECTION("operator/(std::size_t)")
     {
         // json_pointer::operator/=(std::size_t) must compile without string_t

tests/src/unit-bson.cpp

@@ -1311,7 +1311,7 @@ TEST_CASE("BSON declared document size bounds the content")
     // records the events that a SAX parser receives
     struct recorder : nlohmann::json_sax<json>
     {
-        std::string events {};
+        std::string events;
 
         bool null() override
         {

tests/src/unit-json_patch.cpp

@@ -2178,13 +2178,8 @@ TEST_CASE("JSON patch - behavior documented in the API reference")
 
     SECTION("patch() has the strong guarantee")
     {
-        // independent values, so that the comparison below checks the untouched document
-        const auto make_doc = []
-        {
-            return R"({"a": [1, 2], "o": {"k": "v"}})"_json;
-        };
-        const json doc = make_doc();
-        const json before = make_doc();
+        const json doc = R"({"a": [1, 2], "o": {"k": "v"}})"_json;
+        const json before = doc;
 
         const std::vector<json> failing =
         {
@@ -2207,7 +2202,7 @@ TEST_CASE("JSON patch - behavior documented in the API reference")
             CHECK_THROWS_AS(doc.patch(patch), json::exception&);
             CHECK(doc == before);
 
-            json copy = make_doc();
+            json copy = doc;
             CHECK_THROWS_AS(copy.patch(patch), json::exception&);
             CHECK(copy == before);
         }

tests/src/unit-json_pointer.cpp

@@ -29,64 +29,9 @@ using nlohmann::json;
 #include <map>
 #include <random>
 #include <sstream>
-#include <stdexcept>
 #include <string>
 #include <vector>
 
-namespace
-{
-// the non-const operator[] must throw for pointer and leave the value parsed
-// from init unchanged (strong exception safety)
-template<typename Json>
-void check_strong_guarantee(const char* init, const std::string& pointer, const char* message)
-{
-    CAPTURE(init)
-    CAPTURE(pointer)
-    Json j = Json::parse(init);
-    const Json before = Json::parse(init);
-    const typename Json::json_pointer ptr(pointer);
-    CHECK_THROWS_WITH_AS(j[ptr], message, typename Json::exception&);
-    CHECK(j == before);
-}
-
-// as above, for an index that fits into size_type, but not into an array
-template<typename Json>
-void check_strong_guarantee_length_error(const char* init, const std::string& pointer)
-{
-    CAPTURE(init)
-    CAPTURE(pointer)
-    Json j = Json::parse(init);
-    const Json before = Json::parse(init);
-    const typename Json::json_pointer ptr(pointer);
-    CHECK_THROWS_AS(j[ptr], std::length_error&);
-    CHECK(j == before);
-}
-
-template<typename Json>
-void check_strong_guarantee_cases()
-{
-    const char* const unresolved = "[json.exception.out_of_range.404] unresolved reference token '99999999999999999999999'";
-
-    // the first change converts a null value
-    check_strong_guarantee<Json>("null", "/99999999999999999999999", unresolved);
-    check_strong_guarantee<Json>("null", "/a/99999999999999999999999", unresolved);
-    check_strong_guarantee<Json>(R"({"a":null})", "/a/b/-/99999999999999999999999", unresolved);
-    // the first change inserts a key into an object
-    check_strong_guarantee<Json>("{}", "/a/99999999999999999999999", unresolved);
-    check_strong_guarantee<Json>(R"({"a":{"b":1}})", "/a/c/d/99999999999999999999999", unresolved);
-    // the first change pads or appends to an array
-    check_strong_guarantee<Json>(R"({"a":[1]})", "/a/5/99999999999999999999999", unresolved);
-    check_strong_guarantee<Json>(R"({"a":[1]})", "/a/-/x/1/99999999999999999999999", unresolved);
-    // an index that does not fit into size_type
-    check_strong_guarantee<Json>("null", "/x/18446744073709551615",
-                                 "[json.exception.out_of_range.410] array index 18446744073709551615 exceeds size_type");
-    // an index that fits into size_type, but not into an array
-    const auto too_large = std::to_string((std::numeric_limits<typename Json::size_type>::max)() - 1);
-    check_strong_guarantee_length_error<Json>("null", "/" + too_large);
-    check_strong_guarantee_length_error<Json>(R"({"a":[[1]]})", "/a/0/3/" + too_large);
-}
-} // namespace
-
 TEST_CASE("JSON pointers")
 {
     SECTION("errors")
@@ -612,23 +557,6 @@ TEST_CASE("JSON pointers")
             CHECK_THROWS_WITH_AS(j.at("/01"_json_pointer),
                                  "[json.exception.parse_error.106] parse error: array index '01' must not begin with '0'", json::parse_error&);
         }
-
-        SECTION("a failing operator[] leaves the value unchanged")
-        {
-            check_strong_guarantee_cases<json>();
-            check_strong_guarantee_cases<nlohmann::ordered_json>();
-        }
-
-        SECTION("a successful operator[] still creates the same values")
-        {
-            json j = {{"a", {1}}};
-            j["/a/3/x/-/y"_json_pointer] = 1;
-            CHECK(j == json::parse(R"({"a":[1,null,null,{"x":[{"y":1}]}]})"));
-            j["/a/-"_json_pointer] = 2;
-            j["/a/0"_json_pointer] = 3;
-            j["/b"_json_pointer] = 4;
-            CHECK(j == json::parse(R"({"a":[3,null,null,{"x":[{"y":1}]},2],"b":4})"));
-        }
     }
 
     SECTION("flatten")

tests/src/unit-json_view.cpp

@@ -749,6 +749,20 @@ std::string exception_of(F f)
     }
     return "";
 }
+
+// the exception a call on a basic_json value throws, without the byte range of
+// the value (JSON_DIAGNOSTIC_POSITIONS), which the exceptions of views lack
+template<typename F>
+std::string json_exception_of(F f)
+{
+    std::string what = exception_of(f);
+    const std::size_t at = what.find("] (bytes ");
+    if (at != std::string::npos)
+    {
+        what.erase(at + 2, what.find(") ", at) - at);
+    }
+    return what;
+}
 #endif
 
 // compares a view with the ordered_json value materialize() gives for it:
@@ -957,24 +971,24 @@ TEST_CASE("json_view element access and iteration")
 #if !defined(JSON_NOEXCEPTION)
             if (!j.is_object())
             {
-                CHECK(exception_of([&] { static_cast<void>(v["a"]); }) == exception_of([&] { static_cast<void>(j["a"]); }));
+                CHECK(exception_of([&] { static_cast<void>(v["a"]); }) == json_exception_of([&] { static_cast<void>(j["a"]); }));
             }
             if (!j.is_array())
             {
-                CHECK(exception_of([&] { static_cast<void>(v[0]); }) == exception_of([&] { static_cast<void>(j[0]); }));
+                CHECK(exception_of([&] { static_cast<void>(v[0]); }) == json_exception_of([&] { static_cast<void>(j[0]); }));
             }
-            CHECK(exception_of([&] { static_cast<void>(v.at("a")); }) == exception_of([&] { static_cast<void>(j.at("a")); }));
-            CHECK(exception_of([&] { static_cast<void>(v.at("missing")); }) == exception_of([&] { static_cast<void>(j.at("missing")); }));
-            CHECK(exception_of([&] { static_cast<void>(v.at(0)); }) == exception_of([&] { static_cast<void>(j.at(0)); }));
-            CHECK(exception_of([&] { static_cast<void>(v.at(5)); }) == exception_of([&] { static_cast<void>(j.at(5)); }));
+            CHECK(exception_of([&] { static_cast<void>(v.at("a")); }) == json_exception_of([&] { static_cast<void>(j.at("a")); }));
+            CHECK(exception_of([&] { static_cast<void>(v.at("missing")); }) == json_exception_of([&] { static_cast<void>(j.at("missing")); }));
+            CHECK(exception_of([&] { static_cast<void>(v.at(0)); }) == json_exception_of([&] { static_cast<void>(j.at(0)); }));
+            CHECK(exception_of([&] { static_cast<void>(v.at(5)); }) == json_exception_of([&] { static_cast<void>(j.at(5)); }));
             if (!(j.is_object() && j.empty())) // (key() of an end iterator)
             {
-                CHECK(exception_of([&] { static_cast<void>(v.begin().key()); }) == exception_of([&] { static_cast<void>(j.begin().key()); }));
+                CHECK(exception_of([&] { static_cast<void>(v.begin().key()); }) == json_exception_of([&] { static_cast<void>(j.begin().key()); }));
             }
             if (!j.empty() || j.is_null())
             {
-                CHECK(exception_of([&] { static_cast<void>(v.front()); }) == exception_of([&] { static_cast<void>(j.front()); }));
-                CHECK(exception_of([&] { static_cast<void>(v.back()); }) == exception_of([&] { static_cast<void>(j.back()); }));
+                CHECK(exception_of([&] { static_cast<void>(v.front()); }) == json_exception_of([&] { static_cast<void>(j.front()); }));
+                CHECK(exception_of([&] { static_cast<void>(v.back()); }) == json_exception_of([&] { static_cast<void>(j.back()); }));
             }
 #endif
             CHECK(v.contains("a") == j.contains("a"));

tests/src/unit-json_view_builder.cpp

@@ -592,7 +592,7 @@ TEST_CASE("json_view node integer bits")
                 })
         {
             CAPTURE(v)
-            n.kind = nlohmann::detail::view::node_kind::link;
+            n.kind = static_cast<nlohmann::detail::view::node_kind>(0x5A);
             n.flags = 0xA5;
             n.extra = 0x1234;
             n.off = 0x89ABCDEFu;
@@ -601,7 +601,7 @@ TEST_CASE("json_view node integer bits")
             CHECK(n.len == static_cast<std::uint32_t>(v));
             CHECK(n.next == static_cast<std::uint32_t>(v >> 32));
             // the other fields are untouched
-            CHECK(n.kind == nlohmann::detail::view::node_kind::link);
+            CHECK(static_cast<std::uint8_t>(n.kind) == 0x5A);
             CHECK(n.flags == 0xA5);
             CHECK(n.extra == 0x1234);
             CHECK(n.off == 0x89ABCDEFu);

tests/src/unit-json_view_from_json.cpp

@@ -326,7 +326,8 @@ TEST_CASE("json_view from_json")
         CHECK(d.root().get<std::unordered_map<std::string, int>>().at("a") == 3);
     }
 
-#if !defined(JSON_NOEXCEPTION) && !JSON_DIAGNOSTICS
+// (the exceptions of views have neither the path nor the byte range of the value)
+#if !defined(JSON_NOEXCEPTION) && !JSON_DIAGNOSTICS && !JSON_DIAGNOSTIC_POSITIONS
     SECTION("std types: the same errors as from the materialized value")
     {
         const json_document d = json_document::parse(R"([[1, "x"], {"a": 1}, "text", [1], 5, null])");
@@ -392,7 +393,7 @@ TEST_CASE("json_view from_json")
 #if !defined(JSON_NOEXCEPTION)
         const json j = d.root().materialize();
         CHECK(exception_of_call([&] { static_cast<void>(d.root()[2].get<strict_color>()); }) == "[json.exception.out_of_range.410] enum value out of range for strict_color: \"purple\"");
-#if !JSON_DIAGNOSTICS
+#if !JSON_DIAGNOSTICS && !JSON_DIAGNOSTIC_POSITIONS
         CHECK(exception_of_call([&] { static_cast<void>(d.root()[2].get<strict_color>()); }) == exception_of_call([&] { static_cast<void>(j[2].get<strict_color>()); }));
 #endif
 #endif
@@ -440,10 +441,11 @@ TEST_CASE("json_view from_json")
         CHECK(o.root().get<shape>().center.y == 2);
     }
 
-#if !defined(JSON_NOEXCEPTION) && !JSON_DIAGNOSTICS
+#if !defined(JSON_NOEXCEPTION) && !JSON_DIAGNOSTICS && !JSON_DIAGNOSTIC_POSITIONS
     SECTION("errors are those of the same conversion of a json value")
     {
-        // (with JSON_DIAGNOSTICS, those of json name the path of the value)
+        // (with JSON_DIAGNOSTICS, those of json name the path of the value,
+        // and with JSON_DIAGNOSTIC_POSITIONS its bytes)
         const json_document d = json_document::parse(R"([{"x": 1}, {"x": "1", "y": 2}, [1, 2], {"id": "7", "c": "red"}])");
         const json j = d.root().materialize();
         for (std::size_t i = 0; i < 3; ++i)

tests/src/unit-json_view_positions.cpp

@@ -0,0 +1,340 @@
+//     __ _____ _____ _____
+//  __|  |   __|     |   | |  JSON for Modern C++ (supporting code)
+// |  |  |__   |  |  | | | |  version 3.12.0
+// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
+//
+// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
+// SPDX-License-Identifier: MIT
+
+// source positions of materialize() (JSON_DIAGNOSTIC_POSITIONS, #5864)
+
+#include "doctest_compatibility.h"
+
+#ifndef JSON_DIAGNOSTICS
+    #define JSON_DIAGNOSTICS 1
+#endif
+#define JSON_DIAGNOSTIC_POSITIONS 1
+#include <nlohmann/json_view.hpp>
+using nlohmann::json;
+using nlohmann::ordered_json;
+using nlohmann::json_document;
+using nlohmann::json_editable_document;
+
+#include <cstdint>
+#include <cstring>
+#include <fstream>
+#include <sstream>
+#include <string>
+#include <vector>
+
+#include "json_view_test_helpers.hpp"
+#include <test_data.hpp>
+
+namespace
+{
+constexpr std::size_t npos = std::string::npos;
+
+// whether every value of a has the source positions of the value of b at the
+// same place (a and b are equal; shallow test documents only)
+template<typename BasicJsonType>
+bool same_positions(const BasicJsonType& a, const BasicJsonType& b)
+{
+    if (a.start_pos() != b.start_pos() || a.end_pos() != b.end_pos() || a.type() != b.type() || a.size() != b.size())
+    {
+        return false;
+    }
+    if (a.is_object())
+    {
+        for (auto it = a.begin(); it != a.end(); ++it)
+        {
+            if (!same_positions(it.value(), b.at(it.key())))
+            {
+                return false;
+            }
+        }
+    }
+    else if (a.is_array())
+    {
+        for (std::size_t i = 0; i < a.size(); ++i)
+        {
+            if (!same_positions(a[i], b[i]))
+            {
+                return false;
+            }
+        }
+    }
+    return true;
+}
+
+// the materialized root of text has the positions of parse()
+template<typename BasicJsonType>
+bool positions_as_parse(const std::string& text, bool comments = false, bool trailing_commas = false)
+{
+    const auto j = BasicJsonType::parse(text, nullptr, true, comments, trailing_commas);
+    const auto d = nlohmann::basic_json_document<BasicJsonType>::parse(text, true, comments, trailing_commas);
+    const auto e = nlohmann::basic_json_document<BasicJsonType, nlohmann::view_mode::editable>::parse(text, true, comments, trailing_commas);
+    return same_positions(d.root().materialize(), j) && same_positions(e.root().materialize(), j);
+}
+
+std::string range(const json& j)
+{
+    return j.start_pos() == npos && j.end_pos() == npos ? "none" : std::to_string(j.start_pos()) + "-" + std::to_string(j.end_pos());
+}
+} // namespace
+
+TEST_CASE("json_view materialize() source positions")
+{
+    SECTION("as parse()")
+    {
+        const std::vector<std::string> texts =
+        {
+            "null", "true", "false", "0", "-12", "3.25e-2", "18446744073709551615", "-9223372036854775809", R"("a")",
+            R"("\n")", R"("\u00e9")", R"("\ud83d\ude00")", "\"\xf0\x9f\x98\x80\"", R"("a\"b\\")", R"("x\\")",
+            "  [ ]  ", "{}", "[[[]]]", R"({"a":{"b":[1,{"c":[]}]}})",
+            R"({"\u0041": "v\n", "k": "\"", "\t":[ "\/" ]})",
+            "[1, 2.5, true, false, null, \"s\", \"\\u0000\", -0]",
+            "\n\t[\r\n  1 ,\n  {\n    \"a\" : [ ]\n  }\n]\n",
+            "\xef\xbb\xbf[1, {\"a\": \"b\"}]", "\xef\xbb\xbf\"\\n\"",
+        };
+        for (const auto& text : texts)
+        {
+            CAPTURE(text)
+            CHECK(positions_as_parse<json>(text));
+            CHECK(positions_as_parse<ordered_json>(text));
+        }
+    }
+
+    SECTION("comments and trailing commas")
+    {
+        const std::vector<std::string> texts =
+        {
+            "[1 /* ] */]", "[1 // ]\n]", "{\"a\": 1 /* } */ , }", "[1, 2, ]", "[[1,],[2 , /**/ ] , ]",
+            "{\"a\": [] // }\n, \"b\": {} /* } ] */ }", "[ /* empty */ ]", "{ // }\n}", "/* a */ [1] // b",
+            "[\"\\n\" /* \" */ , ]",
+        };
+        for (const auto& text : texts)
+        {
+            CAPTURE(text)
+            CHECK(positions_as_parse<json>(text, true, true));
+        }
+    }
+
+    SECTION("generated documents")
+    {
+        json_view_test::generator gen;
+        for (int i = 0; i < 300; ++i)
+        {
+            std::string text;
+            gen.value(text, 0);
+            CAPTURE(text)
+            CHECK(positions_as_parse<json>(text));
+            CHECK(positions_as_parse<ordered_json>(text));
+        }
+    }
+
+    SECTION("test data")
+    {
+        for (const char* name :
+                {
+                    "/json_testsuite/sample.json", "/nativejson-benchmark/canada.json", "/nativejson-benchmark/citm_catalog.json",
+                    "/nativejson-benchmark/twitter.json", "/json_tests/pass1.json"
+                })
+        {
+            CAPTURE(name)
+            const std::ifstream f(std::string(TEST_DATA_DIRECTORY) + name, std::ios::binary);
+            std::stringstream ss;
+            ss << f.rdbuf();
+            CHECK(positions_as_parse<json>(ss.str()));
+        }
+    }
+
+    SECTION("subtrees")
+    {
+        const std::string text = R"({"a": [1, "\n", {"b": null}], "s": "x\ty", "n": -1.5})";
+        const json j = json::parse(text);
+        const json_document d = json_document::parse(text);
+        CHECK(same_positions(d.root()["a"].materialize(), j["a"]));
+        CHECK(same_positions(d.root()["a"][2].materialize(), j["a"][2]));
+        CHECK(same_positions(d.root()["a"][1].materialize(), j["a"][1]));
+        CHECK(same_positions(d.root()["s"].materialize(), j["s"]));
+        CHECK(same_positions(d.root()["n"].materialize(), j["n"]));
+        CHECK(range(d.root()["a"][1].materialize()) == "10-14");
+        CHECK(range(d.root()["s"].materialize()) == "35-41");
+    }
+
+#if !defined(JSON_NOEXCEPTION)
+    SECTION("exception messages")
+    {
+        const std::string text = "{\n  \"address\": {\"street\": \"Fake\\tStreet\", \"housenumber\": \"1\"},\n  \"list\": [1, [true]]\n}";
+        const json j = json::parse(text);
+        const json_document d = json_document::parse(text);
+        const json m = d.root().materialize();
+        const std::string expected = json_view_test::exception_of_call([&]
+        {
+            static_cast<void>(j.at("address").at("housenumber").get<int>());
+        });
+        CHECK(expected.find("(bytes ") != std::string::npos);
+        CHECK(json_view_test::exception_of_call([&]
+        {
+            static_cast<void>(m.at("address").at("housenumber").get<int>());
+        }) == expected);
+        CHECK(json_view_test::exception_of_call([&]
+        {
+            static_cast<void>(m.at("address").at("street").get<int>());
+        }) == json_view_test::exception_of_call([&]
+        {
+            static_cast<void>(j.at("address").at("street").get<int>());
+        }));
+        CHECK(json_view_test::exception_of_call([&]
+        {
+            static_cast<void>(m.at("list").at(1).get<int>());
+        }) == json_view_test::exception_of_call([&]
+        {
+            static_cast<void>(j.at("list").at(1).get<int>());
+        }));
+    }
+#endif
+
+    SECTION("edited documents")
+    {
+        const std::string text = R"({"a": [1, 2], "b": {"c": "\n", "d": true}, "e": [3, [4]], "f": "x"})";
+        const json j = json::parse(text);
+
+        SECTION("new scalars have none")
+        {
+            json_editable_document d = json_editable_document::parse(text);
+            d.set(d.root()["f"], 5);
+            d.set(d.root()["b"]["d"], "s");
+            const json m = d.root().materialize();
+            CHECK(range(m["f"]) == "none");
+            CHECK(range(m["b"]["d"]) == "none");
+            // the object whose last member is new has none; the others keep theirs
+            CHECK(range(m) == "none");
+            CHECK(range(m["b"]) == "none");
+            CHECK(same_positions(m["a"], j["a"]));
+            CHECK(same_positions(m["e"], j["e"]));
+            CHECK(same_positions(m["b"]["c"], j["b"]["c"]));
+        }
+
+        SECTION("containers whose elements change have none")
+        {
+            json_editable_document d = json_editable_document::parse(text);
+            d.push_back(d.root()["a"], 7);
+            d.erase(d.root()["e"], 0);
+            const json m = d.root().materialize();
+            CHECK(range(m["a"]) == "none");
+            CHECK(range(m["a"][2]) == "none");
+            CHECK(range(m["e"]) == "none");
+            // the elements kept keep theirs
+            CHECK(range(m["a"][0]) == range(j["a"][0]));
+            CHECK(range(m["a"][1]) == range(j["a"][1]));
+            CHECK(same_positions(m["e"][0], j["e"][1]));
+            CHECK(same_positions(m["b"], j["b"]));
+            // the root's elements did not change
+            CHECK(range(m) == range(j));
+        }
+
+        SECTION("new containers have none")
+        {
+            json_editable_document d = json_editable_document::parse(text);
+            d.set(d.root()["b"], json::parse(R"({"x": [1]})"));
+            const json m = d.root().materialize();
+            CHECK(range(m["b"]) == "none");
+            CHECK(range(m["b"]["x"]) == "none");
+            CHECK(range(m["b"]["x"][0]) == "none");
+            CHECK(range(m) == range(j));
+        }
+
+        SECTION("copies of scalars of the document keep theirs")
+        {
+            // (a copy of an array or object is a new one; its scalars are the
+            // parsed ones)
+            json_editable_document d = json_editable_document::parse(text);
+            d.set(d.root()["f"], d.root()["e"]);
+            d.set(d.root()["a"], d.root()["b"]["c"]);
+            const json m = d.root().materialize();
+            CHECK(range(m["a"]) == range(j["b"]["c"]));
+            CHECK(range(m["f"]) == "none");
+            CHECK(range(m["f"][1]) == "none");
+            CHECK(range(m["f"][0]) == range(j["e"][0]));
+            CHECK(range(m["f"][1][0]) == range(j["e"][1][0]));
+        }
+    }
+
+#if !(defined(__BYTE_ORDER__) && defined(__ORDER_BIG_ENDIAN__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
+    SECTION("images")
+    {
+        const std::string text = R"({"a\n": ["\u00e9", 1.5, {"b": [true, null]}], "c": "d"})";
+        const json j = json::parse(text);
+
+        SECTION("round trip")
+        {
+            const json_document d = json_document::load(json_document::parse(text).save());
+            CHECK(same_positions(d.root().materialize(), j));
+        }
+
+        SECTION("edited")
+        {
+            json_editable_document e = json_editable_document::parse(text);
+            e.set(e.root()["c"], 1);
+            e.push_back(e.root()[std::string("a") + '\n'], false);
+            e.set(e.root()[std::string("a") + '\n'][2]["b"][0], "\"");
+            const json_document d = json_document::load(e.save());
+            const json m = d.root().materialize();
+            CHECK(range(m["c"]) == "none");
+            CHECK(range(m) == "none");
+            const json& a = m[std::string("a") + '\n'];
+            const json& ja = j[std::string("a") + '\n'];
+            CHECK(range(a) == "none");
+            CHECK(range(a[3]) == "none");
+            CHECK(range(a[0]) == range(ja[0]));
+            CHECK(range(a[1]) == range(ja[1]));
+            CHECK(range(a[2]["b"][0]) == "none");
+            CHECK(range(a[2]["b"][1]) == range(ja[2]["b"][1]));
+            // the last element of b is still the parsed one
+            CHECK(range(a[2]["b"]) == range(ja[2]["b"]));
+            CHECK(range(a[2]) == range(ja[2]));
+        }
+
+        SECTION("without positions")
+        {
+            // an image saved without JSON_DIAGNOSTIC_POSITIONS: next is 0 for
+            // the strings with escapes
+            std::vector<std::uint8_t> image = json_document::parse(text).save();
+            std::uint64_t count = 0;
+            std::memcpy(&count, image.data() + 8, sizeof(count));
+            for (std::size_t i = 0; i < count; ++i)
+            {
+                nlohmann::detail::view::node n{};
+                std::memcpy(&n, image.data() + 64 + (i * sizeof(n)), sizeof(n));
+                if (n.kind == nlohmann::detail::view::node_kind::string)
+                {
+                    n.next = 0;
+                }
+                std::memcpy(image.data() + 64 + (i * sizeof(n)), &n, sizeof(n));
+            }
+            const json_document d = json_document::load(image);
+            const json m = d.root().materialize();
+            CHECK(range(m[std::string("a") + '\n'][0]) == "none");
+            CHECK(range(m["c"]) == range(j["c"]));
+            CHECK(same_positions(m[std::string("a") + '\n'][2], j[std::string("a") + '\n'][2]));
+        }
+
+#if !defined(JSON_NOEXCEPTION)
+        SECTION("a decoded string's position must be within the text")
+        {
+            std::vector<std::uint8_t> image = json_document::parse(R"(["\n"])").save();
+            nlohmann::detail::view::node n{};
+            std::memcpy(&n, image.data() + 64 + sizeof(n), sizeof(n));
+            REQUIRE(n.next == 2);
+            n.next = 7;
+            std::memcpy(image.data() + 64 + sizeof(n), &n, sizeof(n));
+            CHECK_THROWS_AS(json_document::load(image), json::parse_error&);
+            // without the check, the position is out of bounds and ignored
+            const json_document d = json_document::load(image, json_document::image_check::none);
+            CHECK(range(d.root()[0].materialize()) == "none");
+        }
+#endif
+    }
+#endif
+}

tests/src/unit-regression1.cpp

@@ -1499,23 +1499,6 @@ TEST_CASE("regression tests 1")
         CHECK(order.dump() == R"({"a":2,"m":{"y":1,"b":2},"new_key":3})");
     }
 
-    SECTION("operator[](json_pointer) when emplace() finds a key the lookup does not")
-    {
-        // a copied fifo_map restarts its timestamps, so a new key "k" gets
-        // the timestamp of "x": the lookup does not find "k", but emplace()
-        // finds "x" and inserts nothing; the pointer then continues with the
-        // member of "x", as basic_json::operator[] does
-        const my_json orig = my_json::parse(R"({"x":1})");
-        const std::array<const char*, 3> pointers = {{"/k/0", "/k/a/b", "/k/-"}};
-        for (const char* pointer : pointers)
-        {
-            CAPTURE(pointer)
-            my_json j = orig;
-            CHECK_THROWS_AS(j[my_json::json_pointer(pointer)], my_json::out_of_range&);
-            CHECK(j.dump() == R"({"x":1})");
-        }
-    }
-
     SECTION("issue #977 - Assigning between different json types")
     {
         foo_json lj = ns::foo{3};