Merge remote-tracking branch 'origin/develop' into claude/fix-issue-3989-db7e45

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

# Conflicts:
#	tests/src/unit-alt-string.cpp

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

@@ -238,5 +238,7 @@ Strong exception safety: if an exception occurs, the original value stays intact
 
 1. Added in version 1.0.0.
 2. Added in version 1.0.0.
-3. Added in version 3.11.0.
+3. Added in version 3.11.0. Fixed in version 3.13.0 to consistently accept `std::string_view`-convertible keys, as
+   already supported by [`operator[]`](operator[].md), [`value`](value.md), [`find`](find.md), and other lookup
+   functions.
 4. Added in version 2.0.0.

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

@@ -293,6 +293,15 @@ 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"
@@ -466,7 +475,8 @@ 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.
+4. Since version 3.2.0. Explicit for different string types if `JSON_USE_IMPLICIT_CONVERSIONS` is `0` since
+   version 3.13.0.
 5. Since version 1.0.0.
 6. Since version 1.0.0.
 7. Since version 1.0.0. Fixed in version 3.13.0 to also check the iterator range for binary values; before, a range

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

@@ -131,7 +131,9 @@ Logarithmic in the size of the JSON object.
 ## Version history
 
 1. Added in version 3.11.0.
-2. Added in version 3.6.0. Extended template `KeyType` to support comparable types in version 3.11.0.
+2. Added in version 3.6.0. Extended template `KeyType` to support comparable types in version 3.11.0. Fixed in
+   version 3.13.0 to consistently accept `std::string_view`-convertible keys, as already supported by
+   [`operator[]`](operator[].md), [`at`](at.md), [`value`](value.md), and other lookup functions.
 3. Added in version 3.7.0.
 4. Deleted overloads for integral key types added in version 3.13.0 to reject such calls at compile time instead of
    causing undefined behavior at runtime.

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

@@ -84,6 +84,8 @@ Logarithmic in the size of the JSON object.
 ## Version history
 
 1. Added in version 3.11.0.
-2. Added in version 1.0.0. Changed parameter `key` type to `KeyType&&` in version 3.11.0.
+2. Added in version 1.0.0. Changed parameter `key` type to `KeyType&&` in version 3.11.0. Fixed in version 3.13.0 to
+   consistently accept `std::string_view`-convertible keys, as already supported by [`operator[]`](operator[].md),
+   [`at`](at.md), [`value`](value.md), and other lookup functions.
 3. Deleted overload for integral key types added in version 3.13.0 to reject such calls at compile time instead of
    causing undefined behavior at runtime.

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

@@ -70,3 +70,5 @@ Logarithmic in the size of the container, O(log(`size()`)).
 ## Version history
 
 - Since version 2.0.8.
+- Fixed in version 3.13.0: for [`ordered_json`](../ordered_json.md), the value could previously only be passed as an
+  rvalue; it can now also be passed as an lvalue or a `#!cpp const` lvalue, matching the behavior of `json`.

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

@@ -213,5 +213,7 @@ Strong exception safety: if an exception occurs, the original value stays intact
 1. Added in version 1.0.0. Added support for binary types in version 3.8.0.
 2. Added in version 1.0.0. Added support for binary types in version 3.8.0.
 3. Added in version 1.0.0.
-4. Added in version 3.11.0.
+4. Added in version 3.11.0. Fixed in version 3.13.0 to consistently accept `std::string_view`-convertible keys, as
+   already supported by [`operator[]`](operator[].md), [`at`](at.md), [`value`](value.md), and other lookup
+   functions.
 5. Added in version 1.0.0.

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

@@ -88,6 +88,8 @@ Logarithmic in the size of the JSON object.
 ## Version history
 
 1. Added in version 3.11.0.
-2. Added in version 1.0.0. Changed to support comparable types in version 3.11.0.
+2. Added in version 1.0.0. Changed to support comparable types in version 3.11.0. Fixed in version 3.13.0 to
+   consistently accept `std::string_view`-convertible keys, as already supported by [`operator[]`](operator[].md),
+   [`at`](at.md), [`value`](value.md), and other lookup functions.
 3. Deleted overloads for integral key types added in version 3.13.0 to reject such calls at compile time instead of
    causing undefined behavior at runtime.

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

@@ -89,6 +89,9 @@ Strong exception safety: if an exception occurs, the original value stays intact
     - Throws [`out_of_range.410`](../../home/exceptions.md#jsonexceptionout_of_range410) if an array index in the passed
       JSON pointer `ptr` exceeds the range of `size_type` (e.g., on 32-bit platforms).
 
+    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.
+
 ## Complexity
 
 1. Constant if `idx` is in the range of the array. Otherwise, linear in `idx - size()`.
@@ -103,9 +106,12 @@ Strong exception safety: if an exception occurs, the original value stays intact
     The following cases apply to the **const** overloads; the non-const overloads instead insert the missing element
     (see the notes below).
 
-    1. If the element at index `idx` does not exist, the behavior is undefined.
+    1. If the element at index `idx` does not exist, the behavior is undefined and is **guarded by a
+       [runtime assertion](../../features/assertions.md)**!
     2. If the element with key `key` does not exist, the behavior is undefined and is **guarded by a
        [runtime assertion](../../features/assertions.md)**!
+    3. If the JSON pointer `ptr` refers to an object key or an array index that does not exist, the behavior is
+       undefined and is **guarded by a [runtime assertion](../../features/assertions.md)**!
 
 1. The non-const version may add values: If `idx` is beyond the range of the array (i.e., `idx >= size()`), then the
    array is silently filled up with `#!json null` values to make `idx` a valid reference to the last stored element. In
@@ -273,9 +279,11 @@ Strong exception safety: if an exception occurs, the original value stays intact
 ## Version history
 
 1. Added in version 1.0.0. Fixed in version 3.13.0 to throw `#!cpp std::length_error` instead of emptying the array and
-   accessing it out of bounds when `idx` equals the maximum value of `size_type`.
+   accessing it out of bounds when `idx` equals the maximum value of `size_type`. A missing index in the const version
+   is guarded by a runtime assertion since version 3.13.0.
 2. Added in version 1.0.0. Added overloads for `T* key` in version 1.1.0. Removed overloads for `T* key` (replaced by 3)
    in version 3.11.0.
 3. Added in version 3.11.0. Fixed in version 3.13.0 to consistently accept `std::string_view`-convertible keys, as
    already supported by [`at`](at.md), [`value`](value.md), [`find`](find.md), and other lookup functions.
-4. Added in version 2.0.0.
+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.

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

@@ -5,17 +5,17 @@
 bool operator==(const_reference lhs, const_reference rhs) noexcept;   // (1)
 
 template<typename ScalarType>
-bool operator==(const_reference lhs, const ScalarType rhs) noexcept;  // (2)
+bool operator==(const_reference lhs, const ScalarType rhs) noexcept(/* see below */); // (2)
 
 template<typename ScalarType>
-bool operator==(ScalarType lhs, const const_reference rhs) noexcept;  // (2)
+bool operator==(ScalarType lhs, const const_reference rhs) noexcept(/* see below */); // (2)
 
 // since C++20
 class basic_json {
     bool operator==(const_reference rhs) const noexcept;              // (1)
 
     template<typename ScalarType>
-    bool operator==(ScalarType rhs) const noexcept;                   // (2)
+    bool operator==(ScalarType rhs) const noexcept(/* see below */); // (2)
 };
 ```
 
@@ -46,7 +46,12 @@ whether the values `lhs`/`*this` and `rhs` are equal
 
 ## Exception safety
 
-No-throw guarantee: this function never throws exceptions.
+1. No-throw guarantee: this function never throws exceptions.
+2. No-throw guarantee if converting the scalar to a JSON value cannot throw, as for numbers, Booleans, and
+   `#!cpp nullptr`; the function is `#!cpp noexcept` exactly in that case. Otherwise, it throws what the conversion
+   throws, for example `std::bad_alloc` when converting a string, or
+   [`out_of_range.410`](../../home/exceptions.md#jsonexceptionout_of_range410) for an enum value not mapped by
+   [`NLOHMANN_JSON_SERIALIZE_ENUM_STRICT`](../macros/nlohmann_json_serialize_enum_strict.md).
 
 ## Complexity
 
@@ -171,3 +176,4 @@ Linear.
 
 1. Added in version 1.0.0. Added C++20 member functions in version 3.11.0.
 2. Added in version 1.0.0. Added C++20 member functions in version 3.11.0.
+   Made conditionally `#!cpp noexcept` in version 3.13.0; before, a throwing conversion called `std::terminate`.

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

@@ -5,10 +5,10 @@
 bool operator>=(const_reference lhs, const_reference rhs) noexcept;   // (1)
 
 template<typename ScalarType>
-bool operator>=(const_reference lhs, const ScalarType rhs) noexcept;  // (2)
+bool operator>=(const_reference lhs, const ScalarType rhs) noexcept(/* see below */); // (2)
 
 template<typename ScalarType>
-bool operator>=(ScalarType lhs, const const_reference rhs) noexcept;  // (2)
+bool operator>=(ScalarType lhs, const const_reference rhs) noexcept(/* see below */); // (2)
 ```
 
 1. Compares whether one JSON value `lhs` is greater than or equal to another JSON value `rhs` according to the following
@@ -39,7 +39,12 @@ whether `lhs` is greater than or equal to `rhs`
 
 ## Exception safety
 
-No-throw guarantee: this function never throws exceptions.
+1. No-throw guarantee: this function never throws exceptions.
+2. No-throw guarantee if converting the scalar to a JSON value cannot throw, as for numbers, Booleans, and
+   `#!cpp nullptr`; the function is `#!cpp noexcept` exactly in that case. Otherwise, it throws what the conversion
+   throws, for example `std::bad_alloc` when converting a string, or
+   [`out_of_range.410`](../../home/exceptions.md#jsonexceptionout_of_range410) for an enum value not mapped by
+   [`NLOHMANN_JSON_SERIALIZE_ENUM_STRICT`](../macros/nlohmann_json_serialize_enum_strict.md).
 
 ## Complexity
 
@@ -94,3 +99,4 @@ Linear.
 
 1. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
 2. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
+   Made conditionally `#!cpp noexcept` in version 3.13.0; before, a throwing conversion called `std::terminate`.

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

@@ -5,10 +5,10 @@
 bool operator>(const_reference lhs, const_reference rhs) noexcept;   // (1)
 
 template<typename ScalarType>
-bool operator>(const_reference lhs, const ScalarType rhs) noexcept;  // (2)
+bool operator>(const_reference lhs, const ScalarType rhs) noexcept(/* see below */); // (2)
 
 template<typename ScalarType>
-bool operator>(ScalarType lhs, const const_reference rhs) noexcept;  // (2)
+bool operator>(ScalarType lhs, const const_reference rhs) noexcept(/* see below */); // (2)
 ```
 
 1. Compares whether one JSON value `lhs` is greater than another JSON value `rhs` according to the
@@ -39,7 +39,12 @@ whether `lhs` is greater than `rhs`
 
 ## Exception safety
 
-No-throw guarantee: this function never throws exceptions.
+1. No-throw guarantee: this function never throws exceptions.
+2. No-throw guarantee if converting the scalar to a JSON value cannot throw, as for numbers, Booleans, and
+   `#!cpp nullptr`; the function is `#!cpp noexcept` exactly in that case. Otherwise, it throws what the conversion
+   throws, for example `std::bad_alloc` when converting a string, or
+   [`out_of_range.410`](../../home/exceptions.md#jsonexceptionout_of_range410) for an enum value not mapped by
+   [`NLOHMANN_JSON_SERIALIZE_ENUM_STRICT`](../macros/nlohmann_json_serialize_enum_strict.md).
 
 ## Complexity
 
@@ -84,3 +89,4 @@ Linear.
 
 1. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
 2. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
+   Made conditionally `#!cpp noexcept` in version 3.13.0; before, a throwing conversion called `std::terminate`.

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

@@ -5,10 +5,10 @@
 bool operator<=(const_reference lhs, const_reference rhs) noexcept;   // (1)
 
 template<typename ScalarType>
-bool operator<=(const_reference lhs, const ScalarType rhs) noexcept;  // (2)
+bool operator<=(const_reference lhs, const ScalarType rhs) noexcept(/* see below */); // (2)
 
 template<typename ScalarType>
-bool operator<=(ScalarType lhs, const const_reference rhs) noexcept;  // (2)
+bool operator<=(ScalarType lhs, const const_reference rhs) noexcept(/* see below */); // (2)
 ```
 
 1. Compares whether one JSON value `lhs` is less than or equal to another JSON value `rhs`
@@ -40,7 +40,12 @@ whether `lhs` is less than or equal to `rhs`
 
 ## Exception safety
 
-No-throw guarantee: this function never throws exceptions.
+1. No-throw guarantee: this function never throws exceptions.
+2. No-throw guarantee if converting the scalar to a JSON value cannot throw, as for numbers, Booleans, and
+   `#!cpp nullptr`; the function is `#!cpp noexcept` exactly in that case. Otherwise, it throws what the conversion
+   throws, for example `std::bad_alloc` when converting a string, or
+   [`out_of_range.410`](../../home/exceptions.md#jsonexceptionout_of_range410) for an enum value not mapped by
+   [`NLOHMANN_JSON_SERIALIZE_ENUM_STRICT`](../macros/nlohmann_json_serialize_enum_strict.md).
 
 ## Complexity
 
@@ -95,3 +100,4 @@ Linear.
 
 1. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
 2. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
+   Made conditionally `#!cpp noexcept` in version 3.13.0; before, a throwing conversion called `std::terminate`.

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

@@ -5,10 +5,10 @@
 bool operator<(const_reference lhs, const_reference rhs) noexcept;   // (1)
 
 template<typename ScalarType>
-bool operator<(const_reference lhs, const ScalarType rhs) noexcept;  // (2)
+bool operator<(const_reference lhs, const ScalarType rhs) noexcept(/* see below */); // (2)
 
 template<typename ScalarType>
-bool operator<(ScalarType lhs, const const_reference rhs) noexcept;  // (2)
+bool operator<(ScalarType lhs, const const_reference rhs) noexcept(/* see below */); // (2)
 ```
 
 1. Compares whether one JSON value `lhs` is less than another JSON value `rhs` according to the
@@ -49,7 +49,12 @@ whether `lhs` is less than `rhs`
 
 ## Exception safety
 
-No-throw guarantee: this function never throws exceptions.
+1. No-throw guarantee: this function never throws exceptions.
+2. No-throw guarantee if converting the scalar to a JSON value cannot throw, as for numbers, Booleans, and
+   `#!cpp nullptr`; the function is `#!cpp noexcept` exactly in that case. Otherwise, it throws what the conversion
+   throws, for example `std::bad_alloc` when converting a string, or
+   [`out_of_range.410`](../../home/exceptions.md#jsonexceptionout_of_range410) for an enum value not mapped by
+   [`NLOHMANN_JSON_SERIALIZE_ENUM_STRICT`](../macros/nlohmann_json_serialize_enum_strict.md).
 
 ## Complexity
 
@@ -94,3 +99,4 @@ Linear.
 
 1. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
 2. Added in version 1.0.0. Conditionally removed since C++20 in version 3.11.0.
+   Made conditionally `#!cpp noexcept` in version 3.13.0; before, a throwing conversion called `std::terminate`.

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

@@ -5,10 +5,10 @@
 bool operator!=(const_reference lhs, const_reference rhs) noexcept;   // (1)
 
 template<typename ScalarType>
-bool operator!=(const_reference lhs, const ScalarType rhs) noexcept;  // (2)
+bool operator!=(const_reference lhs, const ScalarType rhs) noexcept(/* see below */); // (2)
 
 template<typename ScalarType>
-bool operator!=(ScalarType lhs, const const_reference rhs) noexcept;  // (2)
+bool operator!=(ScalarType lhs, const const_reference rhs) noexcept(/* see below */); // (2)
 ```
 
 1. Compares two JSON values for inequality. Returns `#!cpp !(lhs == rhs)`.
@@ -36,7 +36,12 @@ whether the values `lhs`/`*this` and `rhs` are not equal
 
 ## Exception safety
 
-No-throw guarantee: this function never throws exceptions.
+1. No-throw guarantee: this function never throws exceptions.
+2. No-throw guarantee if converting the scalar to a JSON value cannot throw, as for numbers, Booleans, and
+   `#!cpp nullptr`; the function is `#!cpp noexcept` exactly in that case. Otherwise, it throws what the conversion
+   throws, for example `std::bad_alloc` when converting a string, or
+   [`out_of_range.410`](../../home/exceptions.md#jsonexceptionout_of_range410) for an enum value not mapped by
+   [`NLOHMANN_JSON_SERIALIZE_ENUM_STRICT`](../macros/nlohmann_json_serialize_enum_strict.md).
 
 ## Complexity
 
@@ -98,3 +103,4 @@ Linear.
    member function in version 3.13.0; since C++20, the compiler rewrites `a != b` using `operator==`.
 2. Added in version 1.0.0. Changed in version 3.13.0 to remove special-casing for `NaN` and `discarded` values;
    `operator!=` now consistently means `!(a == b)`. Since C++20, the compiler rewrites `a != b` using `operator==`.
+   Made conditionally `#!cpp noexcept` in version 3.13.0; before, a throwing conversion called `std::terminate`.

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

@@ -6,7 +6,7 @@ class basic_json {
     std::partial_ordering operator<=>(const_reference rhs) const noexcept;  // (1)
 
     template<typename ScalarType>
-    std::partial_ordering operator<=>(const ScalarType rhs) const noexcept; // (2)
+    std::partial_ordering operator<=>(const ScalarType rhs) const noexcept(/* see below */); // (2)
 };
 ```
 
@@ -39,7 +39,12 @@ the `std::partial_ordering` of the 3-way comparison of `*this` and `rhs`
 
 ## Exception safety
 
-No-throw guarantee: this function never throws exceptions.
+1. No-throw guarantee: this function never throws exceptions.
+2. No-throw guarantee if converting the scalar to a JSON value cannot throw, as for numbers, Booleans, and
+   `#!cpp nullptr`; the function is `#!cpp noexcept` exactly in that case. Otherwise, it throws what the conversion
+   throws, for example `std::bad_alloc` when converting a string, or
+   [`out_of_range.410`](../../home/exceptions.md#jsonexceptionout_of_range410) for an enum value not mapped by
+   [`NLOHMANN_JSON_SERIALIZE_ENUM_STRICT`](../macros/nlohmann_json_serialize_enum_strict.md).
 
 ## Complexity
 
@@ -98,3 +103,4 @@ Linear.
 
 1. Added in version 3.11.0.
 2. Added in version 3.11.0.
+   Made conditionally `#!cpp noexcept` in version 3.13.0; before, a throwing conversion called `std::terminate`.

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

@@ -222,7 +222,9 @@ changes to any JSON value.
 1. Added in version 1.0.0. Changed parameter `default_value` type from `const ValueType&` to `ValueType&&` in version
    3.11.0. Deleted overload for integral key types added in version 3.13.0 to reject such calls at compile time
    instead of causing undefined behavior at runtime.
-2. Added in version 3.11.0. Made `ValueType` the first template parameter in version 3.11.2.
+2. Added in version 3.11.0. Made `ValueType` the first template parameter in version 3.11.2. Fixed in version 3.13.0
+   to consistently accept `std::string_view`-convertible keys, as already supported by
+   [`operator[]`](operator[].md), [`at`](at.md), [`find`](find.md), and other lookup functions.
 3. Added in version 2.0.2. Extended to work with arrays in version 3.13.0, including fixing an issue where resolving
    `ptr` through an array unexpectedly threw `out_of_range` instead of returning the resolved element (or
    `default_value`, as documented).

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

@@ -5,7 +5,9 @@
 ```
 
 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).
+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).
 
 ## Default definition
 
@@ -59,6 +61,25 @@ 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)
@@ -68,3 +89,4 @@ 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.

docs/mkdocs/docs/api/macros/json_use_legacy_discarded_value_comparison.md

@@ -81,3 +81,6 @@ When the macro is not defined, the library will define it to its default value.
 ## Version history
 
 - Added in version 3.11.0.
+- Fixed in version 3.13.0 so `<=` and `>=` also emulate the legacy behavior in C++20 when the JSON value is the
+  right-hand operand of a scalar comparison; before, only the 3-way-comparison-rewritten candidate was found, which
+  yielded `#!cpp false` instead of `#!cpp true`.