Merge branch 'develop' into fix/json_pointer_create_object_5357

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

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

@@ -272,15 +272,6 @@ basic_json(basic_json&& other) noexcept;
         When used without parentheses around an empty initializer list, `basic_json()` is called instead of this
         function, yielding the JSON `#!json null` value.
 
-- Overload 4:
-
-    !!! info "Implicit conversion"
-
-        The conversion is implicit unless [`JSON_USE_IMPLICIT_CONVERSIONS`](../macros/json_use_implicit_conversions.md)
-        is defined to `0` and `BasicJsonType::string_t` differs from `string_t`. In that case, the constructor is
-        `explicit`, so a JSON value with a different string type is no longer silently converted, for example when it is
-        passed to a function taking `#!cpp const json&`. Write `#!cpp json(other)` or `#!cpp other.get<json>()` instead.
-
 - Overload 7:
 
     !!! info "Preconditions"
@@ -429,8 +420,7 @@ basic_json(basic_json&& other) noexcept;
 1. Since version 1.0.0.
 2. Since version 1.0.0.
 3. Since version 2.1.0.
-4. Since version 3.2.0. Explicit for different string types if `JSON_USE_IMPLICIT_CONVERSIONS` is `0` since
-   version 3.13.0.
+4. Since version 3.2.0.
 5. Since version 1.0.0.
 6. Since version 1.0.0.
 7. Since version 1.0.0.

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

@@ -128,10 +128,13 @@ Strong exception safety: if an exception occurs, the original value stays intact
 
         When the JSON pointer traverses intermediate levels that don't exist at all yet (not just a missing
         leaf), each missing level is created as an array or an object depending on whether the corresponding
-        pointer token parses as a non-negative integer: a numeric token creates an array, a non-numeric token
-        creates an object. For example, on an initially `#!json null` value, `/foo/0/0/0` creates nested arrays,
-        while `/foo/one/one/one` creates nested objects. This is not specified by the JSON Pointer RFC; it is
-        this library's own, intentional disambiguation rule. See also [JSON Pointer](../../features/json_pointer.md).
+        pointer token is a valid array index: the token `0`, a sequence of digits that does not begin with `0`,
+        or the token `-` creates an array, and every other token creates an object. For example, on an
+        initially `#!json null` value, `/foo/0/0/0` creates nested arrays, while `/foo/one/one/one` creates
+        nested objects. Tokens such as `01` or the empty token cannot be array indices (cf. RFC 6901, Sect. 4)
+        and therefore create objects, just as they would if the level already existed as an object. This is not
+        specified by the JSON Pointer RFC; it is this library's own, intentional disambiguation rule. See also
+        [JSON Pointer](../../features/json_pointer.md).
 
 ## Examples
 

docs/mkdocs/docs/api/macros/json_use_implicit_conversions.md

@@ -5,9 +5,7 @@
 ```
 
 When defined to `0`, implicit conversions are switched off. By default, implicit conversions are switched on. The
-value directly affects [`operator ValueType`](../basic_json/operator_ValueType.md) and the
-[converting constructor](../basic_json/basic_json.md) from a `basic_json` specialization with a different string
-type (overload 4).
+value directly affects [`operator ValueType`](../basic_json/operator_ValueType.md).
 
 ## Default definition
 
@@ -59,25 +57,6 @@ By default, implicit conversions are enabled.
     auto s = j.get<std::string>();
     ```
 
-??? example "Conversion between `basic_json` specializations"
-
-    A `basic_json` specialization with a different string type is also no longer converted implicitly when
-    `JSON_USE_IMPLICIT_CONVERSIONS` is defined to `0`:
-
-    ```cpp
-    using wjson = nlohmann::basic_json<std::map, std::vector, std::wstring>;
-
-    void load(const nlohmann::json& j);
-
-    wjson wj = /* ... */;
-    load(wj);                            // error: no implicit conversion
-    load(nlohmann::json(wj));            // OK: explicit conversion
-    load(wj.get<nlohmann::json>());      // OK: explicit conversion
-    ```
-
-    Specializations that share the same string type, such as `json` and `ordered_json`, remain implicitly
-    convertible.
-
 ## See also
 
 - [**operator ValueType**](../basic_json/operator_ValueType.md) - get a value (implicit)
@@ -87,4 +66,3 @@ By default, implicit conversions are enabled.
 ## Version history
 
 - Added in version 3.9.0.
-- Also affects the conversion between `basic_json` specializations with different string types since version 3.13.0.

include/nlohmann/detail/conversions/to_json.hpp

@@ -291,9 +291,7 @@ void to_json(BasicJsonType& j, const std::optional<T>& opt) noexcept
 {
     if (opt.has_value())
     {
-        // explicit construction, as the conversion from a basic_json with a different
-        // string type is explicit if JSON_USE_IMPLICIT_CONVERSIONS is 0 (#2649)
-        j = BasicJsonType(*opt);
+        j = *opt;
     }
     else
     {

include/nlohmann/detail/json_pointer.hpp

@@ -416,15 +416,19 @@ class json_pointer
             // convert null values to arrays or objects before continuing
             if (ptr->is_null())
             {
-                // check if the reference token is a number
-                const bool nums =
-                    std::all_of(reference_token.begin(), reference_token.end(),
-                                [](const unsigned char x)
+                // 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)
                 {
                     return std::isdigit(x);
                 });
 
-                // change value to an array for numbers or "-" or to object otherwise
+                // 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;

include/nlohmann/json.hpp

@@ -1605,42 +1605,12 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         assert_invariant();
     }
 
-  private:
-    /// whether a basic_json specialization can be converted implicitly into this one;
-    /// with JSON_USE_IMPLICIT_CONVERSIONS set to 0, this is only the case if both share
-    /// the same string type (see https://github.com/nlohmann/json/issues/2649)
-    template<typename BasicJsonType>
-    using is_implicitly_convertible_basic_json = std::integral_constant < bool,
-          (JSON_USE_IMPLICIT_CONVERSIONS != 0)
-          || std::is_same<typename BasicJsonType::string_t, string_t>::value >;
-
-    /// tag to select the constructor that performs the conversion from another basic_json specialization
-    struct convert_basic_json_tag {};
-
-  public:
     /// @brief create a JSON value from an existing one
     /// @sa https://json.nlohmann.me/api/basic_json/basic_json/
     template < typename BasicJsonType,
                detail::enable_if_t <
-                   detail::is_basic_json<BasicJsonType>::value&& !std::is_same<basic_json, BasicJsonType>::value
-                   && is_implicitly_convertible_basic_json<BasicJsonType>::value, int > = 0 >
+                   detail::is_basic_json<BasicJsonType>::value&& !std::is_same<basic_json, BasicJsonType>::value, int > = 0 >
     basic_json(const BasicJsonType& val)
-        : basic_json(val, convert_basic_json_tag{})
-    {}
-
-    /// @brief create a JSON value from an existing one
-    /// @sa https://json.nlohmann.me/api/basic_json/basic_json/
-    template < typename BasicJsonType,
-               detail::enable_if_t <
-                   detail::is_basic_json<BasicJsonType>::value&& !std::is_same<basic_json, BasicJsonType>::value
-                   && !is_implicitly_convertible_basic_json<BasicJsonType>::value, int > = 0 >
-    explicit basic_json(const BasicJsonType& val)
-        : basic_json(val, convert_basic_json_tag{})
-    {}
-
-  private:
-    template<typename BasicJsonType>
-    basic_json(const BasicJsonType& val, convert_basic_json_tag /*unused*/)
 #if JSON_DIAGNOSTIC_POSITIONS
         : start_position(val.start_pos()),
           end_position(val.end_pos())
@@ -1696,7 +1666,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         assert_invariant();
     }
 
-  public:
     /// @brief create a container (array or object) from an initializer list
     /// @sa https://json.nlohmann.me/api/basic_json/basic_json/
     basic_json(initializer_list_t init,
@@ -2463,7 +2432,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                    int > = 0 >
     BasicJsonType get_impl(detail::priority_tag<2> /*unused*/) const
     {
-        return BasicJsonType(*this);
+        return *this;
     }
 
     /*!
@@ -2602,7 +2571,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                  int> = 0>
     ValueType & get_to(ValueType& v) const
     {
-        v = ValueType(*this);
+        v = *this;
         return v;
     }
 

single_include/nlohmann/json.hpp

@@ -6820,9 +6820,7 @@ void to_json(BasicJsonType& j, const std::optional<T>& opt) noexcept
 {
     if (opt.has_value())
     {
-        // explicit construction, as the conversion from a basic_json with a different
-        // string type is explicit if JSON_USE_IMPLICIT_CONVERSIONS is 0 (#2649)
-        j = BasicJsonType(*opt);
+        j = *opt;
     }
     else
     {
@@ -19062,15 +19060,19 @@ class json_pointer
             // convert null values to arrays or objects before continuing
             if (ptr->is_null())
             {
-                // check if the reference token is a number
-                const bool nums =
-                    std::all_of(reference_token.begin(), reference_token.end(),
-                                [](const unsigned char x)
+                // 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)
                 {
                     return std::isdigit(x);
                 });
 
-                // change value to an array for numbers or "-" or to object otherwise
+                // 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;
@@ -27490,42 +27492,12 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         assert_invariant();
     }
 
-  private:
-    /// whether a basic_json specialization can be converted implicitly into this one;
-    /// with JSON_USE_IMPLICIT_CONVERSIONS set to 0, this is only the case if both share
-    /// the same string type (see https://github.com/nlohmann/json/issues/2649)
-    template<typename BasicJsonType>
-    using is_implicitly_convertible_basic_json = std::integral_constant < bool,
-        (JSON_USE_IMPLICIT_CONVERSIONS != 0)
-        || std::is_same<typename BasicJsonType::string_t, string_t>::value >;
-
-    /// tag to select the constructor that performs the conversion from another basic_json specialization
-    struct convert_basic_json_tag {};
-
-  public:
     /// @brief create a JSON value from an existing one
     /// @sa https://json.nlohmann.me/api/basic_json/basic_json/
     template < typename BasicJsonType,
                detail::enable_if_t <
-                   detail::is_basic_json<BasicJsonType>::value&& !std::is_same<basic_json, BasicJsonType>::value
-                   && is_implicitly_convertible_basic_json<BasicJsonType>::value, int > = 0 >
+                   detail::is_basic_json<BasicJsonType>::value&& !std::is_same<basic_json, BasicJsonType>::value, int > = 0 >
     basic_json(const BasicJsonType& val)
-        : basic_json(val, convert_basic_json_tag{})
-    {}
-
-    /// @brief create a JSON value from an existing one
-    /// @sa https://json.nlohmann.me/api/basic_json/basic_json/
-    template < typename BasicJsonType,
-               detail::enable_if_t <
-                   detail::is_basic_json<BasicJsonType>::value&& !std::is_same<basic_json, BasicJsonType>::value
-                   && !is_implicitly_convertible_basic_json<BasicJsonType>::value, int > = 0 >
-    explicit basic_json(const BasicJsonType& val)
-        : basic_json(val, convert_basic_json_tag{})
-    {}
-
-  private:
-    template<typename BasicJsonType>
-    basic_json(const BasicJsonType& val, convert_basic_json_tag /*unused*/)
 #if JSON_DIAGNOSTIC_POSITIONS
         : start_position(val.start_pos()),
           end_position(val.end_pos())
@@ -27581,7 +27553,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
         assert_invariant();
     }
 
-  public:
     /// @brief create a container (array or object) from an initializer list
     /// @sa https://json.nlohmann.me/api/basic_json/basic_json/
     basic_json(initializer_list_t init,
@@ -28348,7 +28319,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                    int > = 0 >
     BasicJsonType get_impl(detail::priority_tag<2> /*unused*/) const
     {
-        return BasicJsonType(*this);
+        return *this;
     }
 
     /*!
@@ -28487,7 +28458,7 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                  int> = 0>
     ValueType & get_to(ValueType& v) const
     {
-        v = ValueType(*this);
+        v = *this;
         return v;
     }
 

tests/src/unit-alt-string.cpp

@@ -13,7 +13,6 @@
 
 #include <cstdint>
 #include <string>
-#include <type_traits>
 #include <utility>
 #include <vector>
 
@@ -375,39 +374,4 @@ TEST_CASE("alternative string type")
         const auto j2 = j.flatten();
         CHECK(j2.dump() == R"({"/foo/0":"bar","/foo/1":"baz"})");
     }
-
-    SECTION("conversion between basic_json specializations (#2649)")
-    {
-        // explicit conversions are always possible
-        CHECK(std::is_constructible<nlohmann::json, alt_json>::value);
-        CHECK(std::is_constructible<alt_json, nlohmann::json>::value);
-        CHECK(std::is_constructible<nlohmann::json, nlohmann::ordered_json>::value);
-        CHECK(std::is_constructible<nlohmann::ordered_json, nlohmann::json>::value);
-
-        // specializations with the same string type are implicitly convertible
-        CHECK(std::is_convertible<nlohmann::ordered_json, nlohmann::json>::value);
-        CHECK(std::is_convertible<nlohmann::json, nlohmann::ordered_json>::value);
-
-        // specializations with different string types are only implicitly convertible
-        // if implicit conversions are enabled
-#if JSON_USE_IMPLICIT_CONVERSIONS
-        CHECK(std::is_convertible<alt_json, nlohmann::json>::value);
-        CHECK(std::is_convertible<nlohmann::json, alt_json>::value);
-#else
-        CHECK_FALSE(std::is_convertible<alt_json, nlohmann::json>::value);
-        CHECK_FALSE(std::is_convertible<nlohmann::json, alt_json>::value);
-#endif
-
-        // get<BasicJsonType>() works in either case
-        const nlohmann::json j = {{"foo", 1}, {"bar", true}};
-        CHECK(j.get<nlohmann::ordered_json>() == nlohmann::ordered_json(j));
-        // (only a number is converted here, as objects and strings are affected by #3425)
-        CHECK(nlohmann::json(42).get<alt_json>() == 42);
-        CHECK(alt_json(nlohmann::json(42)) == 42);
-
-        // get_to() also works in either case
-        alt_json a;
-        nlohmann::json(42).get_to(a);
-        CHECK(a == 42);
-    }
 }

tests/src/unit-json_pointer.cpp

@@ -438,6 +438,72 @@ TEST_CASE("JSON pointers")
         }
     }
 
+    SECTION("creating intermediate levels")
+    {
+        SECTION("tokens that are valid array indices create arrays")
+        {
+            json j;
+            j["/0"_json_pointer] = 1;
+            CHECK(j == json({1}));
+
+            json j2;
+            j2["/2"_json_pointer] = 1;
+            CHECK(j2 == json({nullptr, nullptr, 1}));
+
+            json j3;
+            j3["/-"_json_pointer] = 1;
+            CHECK(j3 == json({1}));
+
+            json j4;
+            j4["/foo/0/0"_json_pointer] = 1;
+            CHECK(j4 == json({{"foo", {{1}}}}));
+        }
+
+        SECTION("tokens that are no valid array indices create objects")
+        {
+            json j;
+            j["/one"_json_pointer] = 1;
+            CHECK(j == json({{"one", 1}}));
+
+            // leading '0' can never be a valid array index (RFC 6901, Sect. 4)
+            json j2;
+            j2["/01"_json_pointer] = 1;
+            CHECK(j2 == json({{"01", 1}}));
+
+            // the empty token is a valid object key, but no valid array index
+            json j3;
+            j3["/"_json_pointer] = 1;
+            CHECK(j3 == json({{"", 1}}));
+        }
+
+        SECTION("creating a level yields the same result as reusing it (#5357)")
+        {
+            json j;
+            j["/a/b/01/d"_json_pointer] = "value";
+
+            json j_init = json::object();
+            j_init["/a/b"_json_pointer] = json::object();
+            j_init["/a/b/01/d"_json_pointer] = "value";
+
+            const json expected = json::parse(R"({"a":{"b":{"01":{"d":"value"}}}})");
+            CHECK(j == expected);
+            CHECK(j_init == expected);
+
+            // unflatten uses the same key
+            const json flat = {{"/a/b/01/d", "value"}};
+            CHECK(flat.unflatten() == expected);
+        }
+
+        SECTION("existing arrays still reject invalid indices")
+        {
+            json j = {1, 2, 3};
+            CHECK_THROWS_WITH_AS(j["/01"_json_pointer],
+                                 "[json.exception.parse_error.106] parse error: array index '01' must not begin with '0'", json::parse_error&);
+            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("flatten")
     {
         json j =