Throw when JSON Patch remove's target path resolves through a primitive or null parent

RFC 6902 (section 4.2) requires the target location of a "remove"
operation to exist. operation_remove handled parent.is_object() and
parent.is_array(), but had no final else branch: when the resolved
parent was a primitive value or null, neither branch matched and the
operation silently did nothing instead of failing.

Add the missing else branch, throwing out_of_range.413 with wording
that matches the existing out_of_range.411 thrown by the analogous
"add" case (operation_add) for the same kind of invalid parent.

Fixes #5396.

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

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

@@ -34,6 +34,8 @@ Strong guarantee: if an exception is thrown, there are no changes in the JSON va
   ("add", "remove", "move")
 - Throws [`out_of_range.411`](../../home/exceptions.md#jsonexceptionout_of_range411) if an "add" operation's target
   location has a parent that is neither an object nor an array.
+- Throws [`out_of_range.413`](../../home/exceptions.md#jsonexceptionout_of_range413) if a "remove" operation's target
+  location has a parent that is neither an object nor an array.
 - Throws [`other_error.501`](../../home/exceptions.md#jsonexceptionother_error501) if "test" operation was
   unsuccessful.
 
@@ -75,3 +77,5 @@ is thrown. In any case, the original value is not changed: the patch is applied
 - Added in version 2.0.0.
 - Added [`out_of_range.411`](../../home/exceptions.md#jsonexceptionout_of_range411) and stopped relying on an internal assertion when an "add" operation's
   target location has a non-object/non-array parent in version 3.13.0.
+- Added [`out_of_range.413`](../../home/exceptions.md#jsonexceptionout_of_range413) and stopped silently ignoring a "remove" operation whose target
+  location has a non-object/non-array parent in version 3.13.0.

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

@@ -30,6 +30,8 @@ No guarantees, value may be corrupted by an unsuccessful patch operation.
   ("add", "remove", "move")
 - Throws [`out_of_range.411`](../../home/exceptions.md#jsonexceptionout_of_range411) if an "add" operation's target
   location has a parent that is neither an object nor an array.
+- Throws [`out_of_range.413`](../../home/exceptions.md#jsonexceptionout_of_range413) if a "remove" operation's target
+  location has a parent that is neither an object nor an array.
 - Throws [`other_error.501`](../../home/exceptions.md#jsonexceptionother_error501) if "test" operation was
   unsuccessful.
 
@@ -72,3 +74,5 @@ function throws an exception.
 - Added in version 3.11.0.
 - Added [`out_of_range.411`](../../home/exceptions.md#jsonexceptionout_of_range411) and stopped relying on an internal assertion when an "add" operation's
   target location has a non-object/non-array parent in version 3.13.0.
+- Added [`out_of_range.413`](../../home/exceptions.md#jsonexceptionout_of_range413) and stopped silently ignoring a "remove" operation whose target
+  location has a non-object/non-array parent in version 3.13.0.

docs/mkdocs/docs/home/exceptions.md

@@ -933,6 +933,20 @@ BSON stores the length of documents, arrays, strings, and binary values in a sig
     [`to_bson`](../api/basic_json/to_bson.md) produced documents with negative length prefixes that
     [`from_bson`](../api/basic_json/from_bson.md) rejected.
 
+### json.exception.out_of_range.413
+
+A JSON Patch `remove` operation cannot be applied because the target location's parent is neither an object nor an array. Per [RFC 6902](https://datatracker.ietf.org/doc/html/rfc6902), a `remove` target must reference a member of an existing object or an element of an existing array; a primitive value (string, number, boolean, etc.) or `null` has no members or elements to remove.
+
+!!! failure "Example message"
+
+    ```
+    cannot remove value: the JSON Patch 'remove' target's parent is of type number, but must be an object or array
+    ```
+
+!!! note
+
+    This exception was added in version 3.13.0. Before that, this situation was silently ignored (the `remove` operation had no effect).
+
 ## Further exceptions
 
 This exception is thrown in case of errors that cannot be classified with the

include/nlohmann/json.hpp

@@ -1335,7 +1335,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief serialization
     /// @sa https://json.nlohmann.me/api/basic_json/dump/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     string_t dump(const int indent = -1,
                   const char indent_char = ' ',
                   const bool ensure_ascii = false,
@@ -1358,7 +1357,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief return the type of the JSON value (explicit)
     /// @sa https://json.nlohmann.me/api/basic_json/type/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     constexpr value_t type() const noexcept
     {
         return m_data.m_type;
@@ -1366,7 +1364,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief return whether type is primitive
     /// @sa https://json.nlohmann.me/api/basic_json/is_primitive/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     constexpr bool is_primitive() const noexcept
     {
         return is_null() || is_string() || is_boolean() || is_number() || is_binary();
@@ -1374,7 +1371,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief return whether type is structured
     /// @sa https://json.nlohmann.me/api/basic_json/is_structured/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     constexpr bool is_structured() const noexcept
     {
         return is_array() || is_object();
@@ -1382,7 +1378,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief return whether value is null
     /// @sa https://json.nlohmann.me/api/basic_json/is_null/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     constexpr bool is_null() const noexcept
     {
         return m_data.m_type == value_t::null;
@@ -1390,7 +1385,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief return whether value is a boolean
     /// @sa https://json.nlohmann.me/api/basic_json/is_boolean/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     constexpr bool is_boolean() const noexcept
     {
         return m_data.m_type == value_t::boolean;
@@ -1398,7 +1392,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief return whether value is a number
     /// @sa https://json.nlohmann.me/api/basic_json/is_number/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     constexpr bool is_number() const noexcept
     {
         return is_number_integer() || is_number_float();
@@ -1406,7 +1399,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief return whether value is an integer number
     /// @sa https://json.nlohmann.me/api/basic_json/is_number_integer/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     constexpr bool is_number_integer() const noexcept
     {
         return m_data.m_type == value_t::number_integer || m_data.m_type == value_t::number_unsigned;
@@ -1414,7 +1406,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief return whether value is an unsigned integer number
     /// @sa https://json.nlohmann.me/api/basic_json/is_number_unsigned/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     constexpr bool is_number_unsigned() const noexcept
     {
         return m_data.m_type == value_t::number_unsigned;
@@ -1422,7 +1413,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief return whether value is a floating-point number
     /// @sa https://json.nlohmann.me/api/basic_json/is_number_float/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     constexpr bool is_number_float() const noexcept
     {
         return m_data.m_type == value_t::number_float;
@@ -1430,7 +1420,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief return whether value is an object
     /// @sa https://json.nlohmann.me/api/basic_json/is_object/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     constexpr bool is_object() const noexcept
     {
         return m_data.m_type == value_t::object;
@@ -1438,7 +1427,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief return whether value is an array
     /// @sa https://json.nlohmann.me/api/basic_json/is_array/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     constexpr bool is_array() const noexcept
     {
         return m_data.m_type == value_t::array;
@@ -1446,7 +1434,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief return whether value is a string
     /// @sa https://json.nlohmann.me/api/basic_json/is_string/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     constexpr bool is_string() const noexcept
     {
         return m_data.m_type == value_t::string;
@@ -1454,7 +1441,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief return whether value is a binary array
     /// @sa https://json.nlohmann.me/api/basic_json/is_binary/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     constexpr bool is_binary() const noexcept
     {
         return m_data.m_type == value_t::binary;
@@ -1462,7 +1448,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief return whether value is discarded
     /// @sa https://json.nlohmann.me/api/basic_json/is_discarded/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     constexpr bool is_discarded() const noexcept
     {
         return m_data.m_type == value_t::discarded;
@@ -2794,7 +2779,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief returns the number of occurrences of a key in a JSON object
     /// @sa https://json.nlohmann.me/api/basic_json/count/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     size_type count(const typename object_t::key_type& key) const
     {
         // return 0 for all nonobject types
@@ -2805,7 +2789,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/count/
     template<class KeyType, detail::enable_if_t<
                  detail::is_usable_as_basic_json_key_type<basic_json_t, KeyType>::value, int> = 0>
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     size_type count(KeyType && key) const
     {
         // return 0 for all nonobject types
@@ -2814,7 +2797,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief check the existence of an element in a JSON object
     /// @sa https://json.nlohmann.me/api/basic_json/contains/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     bool contains(const typename object_t::key_type& key) const
     {
         return is_object() && m_data.m_value.object->find(key) != m_data.m_value.object->end();
@@ -2824,7 +2806,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/contains/
     template<class KeyType, detail::enable_if_t<
                  detail::is_usable_as_basic_json_key_type<basic_json_t, KeyType>::value, int> = 0>
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     bool contains(KeyType && key) const
     {
         return is_object() && m_data.m_value.object->find(std::forward<KeyType>(key)) != m_data.m_value.object->end();
@@ -2832,14 +2813,12 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief check the existence of an element in a JSON object given a JSON pointer
     /// @sa https://json.nlohmann.me/api/basic_json/contains/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     bool contains(const json_pointer& ptr) const
     {
         return ptr.contains(this);
     }
 
     template<typename BasicJsonType, detail::enable_if_t<detail::is_basic_json<BasicJsonType>::value, int> = 0>
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     JSON_HEDLEY_DEPRECATED_FOR(3.11.0, basic_json::json_pointer or nlohmann::json_pointer<basic_json::string_t>) // NOLINT(readability/alt_tokens)
     bool contains(const typename ::nlohmann::json_pointer<BasicJsonType>& ptr) const
     {
@@ -2995,7 +2974,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief checks whether the container is empty.
     /// @sa https://json.nlohmann.me/api/basic_json/empty/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     bool empty() const noexcept
     {
         switch (m_data.m_type)
@@ -3035,7 +3013,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief returns the number of elements
     /// @sa https://json.nlohmann.me/api/basic_json/size/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     size_type size() const noexcept
     {
         switch (m_data.m_type)
@@ -3075,7 +3052,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief returns the maximum possible number of elements
     /// @sa https://json.nlohmann.me/api/basic_json/max_size/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     size_type max_size() const noexcept
     {
         switch (m_data.m_type)
@@ -4153,7 +4129,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @brief check if the input is valid JSON
     /// @sa https://json.nlohmann.me/api/basic_json/accept/
     template<typename InputType>
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     static bool accept(InputType&& i,
                        const bool ignore_comments = false,
                        const bool ignore_trailing_commas = false)
@@ -4165,7 +4140,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/accept/
     template<typename IteratorType, typename SentinelType = IteratorType,
              detail::enable_if_t<detail::can_compare_ne<IteratorType, SentinelType>::value, int> = 0>
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     static bool accept(IteratorType first, SentinelType last,
                        const bool ignore_comments = false,
                        const bool ignore_trailing_commas = false)
@@ -4265,7 +4239,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief return the type as string
     /// @sa https://json.nlohmann.me/api/basic_json/type_name/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     JSON_HEDLEY_RETURNS_NON_NULL
     const char* type_name() const noexcept
     {
@@ -4966,6 +4939,12 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                 // note erase performs range check
                 parent.erase(json_pointer::template array_index<basic_json_t>(last_path));
             }
+            else
+            {
+                // the parent of a "remove" target must be an object or array
+                // (see #5396)
+                JSON_THROW(out_of_range::create(413, detail::concat("cannot remove value: the JSON Patch 'remove' target's parent is of type ", parent.type_name(), ", but must be an object or array"), &parent));
+            }
         };
 
         // type check: top level value must be an array

single_include/nlohmann/json.hpp

@@ -22763,7 +22763,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief serialization
     /// @sa https://json.nlohmann.me/api/basic_json/dump/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     string_t dump(const int indent = -1,
                   const char indent_char = ' ',
                   const bool ensure_ascii = false,
@@ -22786,7 +22785,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief return the type of the JSON value (explicit)
     /// @sa https://json.nlohmann.me/api/basic_json/type/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     constexpr value_t type() const noexcept
     {
         return m_data.m_type;
@@ -22794,7 +22792,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief return whether type is primitive
     /// @sa https://json.nlohmann.me/api/basic_json/is_primitive/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     constexpr bool is_primitive() const noexcept
     {
         return is_null() || is_string() || is_boolean() || is_number() || is_binary();
@@ -22802,7 +22799,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief return whether type is structured
     /// @sa https://json.nlohmann.me/api/basic_json/is_structured/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     constexpr bool is_structured() const noexcept
     {
         return is_array() || is_object();
@@ -22810,7 +22806,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief return whether value is null
     /// @sa https://json.nlohmann.me/api/basic_json/is_null/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     constexpr bool is_null() const noexcept
     {
         return m_data.m_type == value_t::null;
@@ -22818,7 +22813,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief return whether value is a boolean
     /// @sa https://json.nlohmann.me/api/basic_json/is_boolean/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     constexpr bool is_boolean() const noexcept
     {
         return m_data.m_type == value_t::boolean;
@@ -22826,7 +22820,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief return whether value is a number
     /// @sa https://json.nlohmann.me/api/basic_json/is_number/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     constexpr bool is_number() const noexcept
     {
         return is_number_integer() || is_number_float();
@@ -22834,7 +22827,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief return whether value is an integer number
     /// @sa https://json.nlohmann.me/api/basic_json/is_number_integer/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     constexpr bool is_number_integer() const noexcept
     {
         return m_data.m_type == value_t::number_integer || m_data.m_type == value_t::number_unsigned;
@@ -22842,7 +22834,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief return whether value is an unsigned integer number
     /// @sa https://json.nlohmann.me/api/basic_json/is_number_unsigned/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     constexpr bool is_number_unsigned() const noexcept
     {
         return m_data.m_type == value_t::number_unsigned;
@@ -22850,7 +22841,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief return whether value is a floating-point number
     /// @sa https://json.nlohmann.me/api/basic_json/is_number_float/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     constexpr bool is_number_float() const noexcept
     {
         return m_data.m_type == value_t::number_float;
@@ -22858,7 +22848,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief return whether value is an object
     /// @sa https://json.nlohmann.me/api/basic_json/is_object/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     constexpr bool is_object() const noexcept
     {
         return m_data.m_type == value_t::object;
@@ -22866,7 +22855,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief return whether value is an array
     /// @sa https://json.nlohmann.me/api/basic_json/is_array/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     constexpr bool is_array() const noexcept
     {
         return m_data.m_type == value_t::array;
@@ -22874,7 +22862,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief return whether value is a string
     /// @sa https://json.nlohmann.me/api/basic_json/is_string/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     constexpr bool is_string() const noexcept
     {
         return m_data.m_type == value_t::string;
@@ -22882,7 +22869,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief return whether value is a binary array
     /// @sa https://json.nlohmann.me/api/basic_json/is_binary/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     constexpr bool is_binary() const noexcept
     {
         return m_data.m_type == value_t::binary;
@@ -22890,7 +22876,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief return whether value is discarded
     /// @sa https://json.nlohmann.me/api/basic_json/is_discarded/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     constexpr bool is_discarded() const noexcept
     {
         return m_data.m_type == value_t::discarded;
@@ -24222,7 +24207,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief returns the number of occurrences of a key in a JSON object
     /// @sa https://json.nlohmann.me/api/basic_json/count/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     size_type count(const typename object_t::key_type& key) const
     {
         // return 0 for all nonobject types
@@ -24233,7 +24217,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/count/
     template<class KeyType, detail::enable_if_t<
                  detail::is_usable_as_basic_json_key_type<basic_json_t, KeyType>::value, int> = 0>
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     size_type count(KeyType && key) const
     {
         // return 0 for all nonobject types
@@ -24242,7 +24225,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief check the existence of an element in a JSON object
     /// @sa https://json.nlohmann.me/api/basic_json/contains/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     bool contains(const typename object_t::key_type& key) const
     {
         return is_object() && m_data.m_value.object->find(key) != m_data.m_value.object->end();
@@ -24252,7 +24234,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/contains/
     template<class KeyType, detail::enable_if_t<
                  detail::is_usable_as_basic_json_key_type<basic_json_t, KeyType>::value, int> = 0>
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     bool contains(KeyType && key) const
     {
         return is_object() && m_data.m_value.object->find(std::forward<KeyType>(key)) != m_data.m_value.object->end();
@@ -24260,14 +24241,12 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief check the existence of an element in a JSON object given a JSON pointer
     /// @sa https://json.nlohmann.me/api/basic_json/contains/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     bool contains(const json_pointer& ptr) const
     {
         return ptr.contains(this);
     }
 
     template<typename BasicJsonType, detail::enable_if_t<detail::is_basic_json<BasicJsonType>::value, int> = 0>
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     JSON_HEDLEY_DEPRECATED_FOR(3.11.0, basic_json::json_pointer or nlohmann::json_pointer<basic_json::string_t>) // NOLINT(readability/alt_tokens)
     bool contains(const typename ::nlohmann::json_pointer<BasicJsonType>& ptr) const
     {
@@ -24423,7 +24402,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief checks whether the container is empty.
     /// @sa https://json.nlohmann.me/api/basic_json/empty/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     bool empty() const noexcept
     {
         switch (m_data.m_type)
@@ -24463,7 +24441,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief returns the number of elements
     /// @sa https://json.nlohmann.me/api/basic_json/size/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     size_type size() const noexcept
     {
         switch (m_data.m_type)
@@ -24503,7 +24480,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief returns the maximum possible number of elements
     /// @sa https://json.nlohmann.me/api/basic_json/max_size/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     size_type max_size() const noexcept
     {
         switch (m_data.m_type)
@@ -25581,7 +25557,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @brief check if the input is valid JSON
     /// @sa https://json.nlohmann.me/api/basic_json/accept/
     template<typename InputType>
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     static bool accept(InputType&& i,
                        const bool ignore_comments = false,
                        const bool ignore_trailing_commas = false)
@@ -25593,7 +25568,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
     /// @sa https://json.nlohmann.me/api/basic_json/accept/
     template<typename IteratorType, typename SentinelType = IteratorType,
              detail::enable_if_t<detail::can_compare_ne<IteratorType, SentinelType>::value, int> = 0>
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     static bool accept(IteratorType first, SentinelType last,
                        const bool ignore_comments = false,
                        const bool ignore_trailing_commas = false)
@@ -25693,7 +25667,6 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
 
     /// @brief return the type as string
     /// @sa https://json.nlohmann.me/api/basic_json/type_name/
-    JSON_HEDLEY_WARN_UNUSED_RESULT
     JSON_HEDLEY_RETURNS_NON_NULL
     const char* type_name() const noexcept
     {
@@ -26394,6 +26367,12 @@ class basic_json // NOLINT(cppcoreguidelines-special-member-functions,hicpp-spec
                 // note erase performs range check
                 parent.erase(json_pointer::template array_index<basic_json_t>(last_path));
             }
+            else
+            {
+                // the parent of a "remove" target must be an object or array
+                // (see #5396)
+                JSON_THROW(out_of_range::create(413, detail::concat("cannot remove value: the JSON Patch 'remove' target's parent is of type ", parent.type_name(), ", but must be an object or array"), &parent));
+            }
         };
 
         // type check: top level value must be an array

tests/src/test_utils.hpp

@@ -15,15 +15,6 @@
 namespace utils
 {
 
-// Some tests intentionally discard the [[nodiscard]]/JSON_HEDLEY_WARN_UNUSED_RESULT
-// return value of a call they only make to exercise its side effects (e.g. checking
-// that it does not throw). A plain (void) cast on the call expression does not
-// suppress GCC's warning for functions using the GNU __attribute__((warn_unused_result))
-// form (as opposed to the C++17 [[nodiscard]] attribute) -- passing the value into an
-// ordinary function call does.
-template<typename T>
-inline void ignore_return_value(T&& /*unused*/) noexcept {}
-
 inline std::vector<std::uint8_t> read_binary_file(const std::string& filename)
 {
     std::ifstream file(filename, std::ios::binary);

tests/src/unit-class_parser.cpp

@@ -23,8 +23,6 @@ using nlohmann::json;
 #include <utility>
 #include <vector>
 
-#include "test_utils.hpp"
-
 namespace
 {
 class SaxEventLogger
@@ -626,8 +624,7 @@ TEST_CASE("parser class")
             SECTION("overflow")
             {
                 // overflows during parsing yield an exception
-                // empty() is nodiscard; the exception is thrown by parser_helper() itself, before empty() would run
+                CHECK_THROWS_WITH_AS(parser_helper("1.18973e+4932").empty(), "[json.exception.out_of_range.406] number overflow parsing '1.18973e+4932'", json::out_of_range&);
-                CHECK_THROWS_WITH_AS(utils::ignore_return_value(parser_helper("1.18973e+4932").empty()), "[json.exception.out_of_range.406] number overflow parsing '1.18973e+4932'", json::out_of_range&);
             }
 
             SECTION("invalid numbers")

tests/src/unit-class_parser_diagnostic_positions.cpp

@@ -22,8 +22,6 @@ using nlohmann::json;
 
 #include <valarray>
 
-#include "test_utils.hpp"
-
 namespace
 {
 class SaxEventLogger
@@ -631,8 +629,7 @@ TEST_CASE("parser class")
             SECTION("overflow")
             {
                 // overflows during parsing yield an exception
-                // empty() is nodiscard; the exception is thrown by parser_helper() itself, before empty() would run
+                CHECK_THROWS_WITH_AS(parser_helper("1.18973e+4932").empty(), "[json.exception.out_of_range.406] number overflow parsing '1.18973e+4932'", json::out_of_range&);
-                CHECK_THROWS_WITH_AS(utils::ignore_return_value(parser_helper("1.18973e+4932").empty()), "[json.exception.out_of_range.406] number overflow parsing '1.18973e+4932'", json::out_of_range&);
             }
 
             SECTION("invalid numbers")

tests/src/unit-json_patch.cpp

@@ -1389,6 +1389,61 @@ TEST_CASE("JSON patch - add to a primitive parent (regression #4292)")
     }
 }
 
+TEST_CASE("JSON patch - remove with primitive or null parent (regression #5396)")
+{
+    // Regression test for https://github.com/nlohmann/json/issues/5396
+    //
+    // RFC 6902 (§4.2) requires the target location of a "remove" operation
+    // to exist. When the target's parent resolves to a primitive value or
+    // null, the operation must fail. Previously operation_remove silently
+    // did nothing in this case (neither the "is_object" nor the "is_array"
+    // branch matched, and there was no final "else"), so the patch appeared
+    // to succeed without changing the document. It now throws
+    // out_of_range.413.
+
+    SECTION("parent is a primitive (number)")
+    {
+        json const doc = {{"a", 1}};
+        json const patch = {{{"op", "remove"}, {"path", "/a/b"}}};
+#if JSON_DIAGNOSTICS
+        CHECK_THROWS_WITH_AS(doc.patch(patch), "[json.exception.out_of_range.413] (/a) cannot remove value: the JSON Patch 'remove' target's parent is of type number, but must be an object or array", json::out_of_range&);
+#else
+        CHECK_THROWS_WITH_AS(doc.patch(patch), "[json.exception.out_of_range.413] cannot remove value: the JSON Patch 'remove' target's parent is of type number, but must be an object or array", json::out_of_range&);
+#endif
+    }
+
+    SECTION("parent is a primitive (string)")
+    {
+        json const doc = {{"foo", {{"bar", "a string"}}}};
+        json const patch = {{{"op", "remove"}, {"path", "/foo/bar/baz"}}};
+#if JSON_DIAGNOSTICS
+        CHECK_THROWS_WITH_AS(doc.patch(patch), "[json.exception.out_of_range.413] (/foo/bar) cannot remove value: the JSON Patch 'remove' target's parent is of type string, but must be an object or array", json::out_of_range&);
+#else
+        CHECK_THROWS_WITH_AS(doc.patch(patch), "[json.exception.out_of_range.413] cannot remove value: the JSON Patch 'remove' target's parent is of type string, but must be an object or array", json::out_of_range&);
+#endif
+    }
+
+    SECTION("top-level document is null")
+    {
+        json const doc = nullptr;
+        json const patch = {{{"op", "remove"}, {"path", "/a"}}};
+        CHECK_THROWS_WITH_AS(doc.patch(patch), "[json.exception.out_of_range.413] cannot remove value: the JSON Patch 'remove' target's parent is of type null, but must be an object or array", json::out_of_range&);
+    }
+
+    SECTION("legitimate removes still work")
+    {
+        // object member
+        json const doc1 = {{"a", 1}, {"b", 2}};
+        json const patch1 = {{{"op", "remove"}, {"path", "/a"}}};
+        CHECK(doc1.patch(patch1) == json({{"b", 2}}));
+
+        // array element
+        json const doc2 = R"([1, 2, 3])"_json;
+        json const patch2 = {{{"op", "remove"}, {"path", "/1"}}};
+        CHECK(doc2.patch(patch2) == R"([1, 3])"_json);
+    }
+}
+
 TEST_CASE("JSON patch - diff emits array removals in descending index order")
 {
     SECTION("array shrunk to empty")

tests/src/unit-regression1.cpp

@@ -29,7 +29,6 @@ using nlohmann::json;
 #include <limits>
 #include <cstdio>
 #include "make_test_data_available.hpp"
-#include "test_utils.hpp"
 
 #ifdef JSON_HAS_CPP_17
     #include <variant>
@@ -1374,8 +1373,7 @@ TEST_CASE("regression tests 1")
         std::array<uint8_t, 28> key1 = {{ 103, 92, 117, 48, 48, 48, 55, 92, 114, 215, 126, 214, 95, 92, 34, 174, 40, 71, 38, 174, 40, 71, 38, 223, 134, 247, 127, 0 }};
         std::string const key1_str(reinterpret_cast<char*>(key1.data()));
         json const j = key1_str;
-        // dump() is nodiscard; the exception is thrown by dump() itself before it would return
+        CHECK_THROWS_WITH_AS(j.dump(), "[json.exception.type_error.316] invalid UTF-8 byte at index 10: 0x7E", json::type_error&);
-        CHECK_THROWS_WITH_AS(utils::ignore_return_value(j.dump()), "[json.exception.type_error.316] invalid UTF-8 byte at index 10: 0x7E", json::type_error&);
     }
 
 #if JSON_USE_IMPLICIT_CONVERSIONS

tests/src/unit-regression2.cpp

@@ -31,8 +31,6 @@ using ordered_json = nlohmann::ordered_json;
 #include <type_traits>
 #include <utility>
 
-#include "test_utils.hpp"
-
 #ifdef JSON_HAS_CPP_17
     #include <any>
     #include <variant>
@@ -641,12 +639,7 @@ TEST_CASE("regression tests 2")
                 s += static_cast<char>(i);
             }
             dump_test["1"] = s;
-            // dump() is nodiscard; this only checks that dumping does not throw/crash.
+            dump_test.dump(-1, ' ', true, nlohmann::json::error_handler_t::replace);
-            // A (void) cast on the call itself does not suppress GCC's warning for the
-            // GNU warn_unused_result attribute (unlike a real C++17 [[nodiscard]]), so
-            // capture the result in a variable and discard that instead.
-            auto dump_result = dump_test.dump(-1, ' ', true, nlohmann::json::error_handler_t::replace);
-            (void)dump_result;
         }
     }
 
@@ -738,14 +731,12 @@ TEST_CASE("regression tests 2")
     {
         const std::array<unsigned char, 23> data = {{0x81, 0xA4, 0x64, 0x61, 0x74, 0x61, 0xC4, 0x0F, 0x33, 0x30, 0x30, 0x32, 0x33, 0x34, 0x30, 0x31, 0x30, 0x37, 0x30, 0x35, 0x30, 0x31, 0x30}};
         const json j = json::from_msgpack(data.data(), data.size());
-        // dump() is nodiscard; this only checks that dumping does not throw
         CHECK_NOTHROW(
-            utils::ignore_return_value(
+            j.dump(4,                             // Indent
-                j.dump(4,                             // Indent
+                   ' ',                           // Indent char
-                       ' ',                           // Indent char
+                   false,                         // Ensure ascii
-                       false,                         // Ensure ascii
+                   json::error_handler_t::strict  // Error
-                       json::error_handler_t::strict  // Error
+                  ));
-                      )));
     }
 
     SECTION("PR #2181 - regression bug with lvalue")

tests/src/unit-serialization.cpp

@@ -15,8 +15,6 @@ using nlohmann::json;
 #include <sstream>
 #include <iomanip>
 
-#include "test_utils.hpp"
-
 TEST_CASE("serialization")
 {
     SECTION("operator<<")
@@ -86,9 +84,8 @@ TEST_CASE("serialization")
         {
             const json j = "ä\xA9ü";
 
-            // dump() is nodiscard; the exception is thrown by dump() itself before it would return
+            CHECK_THROWS_WITH_AS(j.dump(), "[json.exception.type_error.316] invalid UTF-8 byte at index 2: 0xA9", json::type_error&);
-            CHECK_THROWS_WITH_AS(utils::ignore_return_value(j.dump()), "[json.exception.type_error.316] invalid UTF-8 byte at index 2: 0xA9", json::type_error&);
+            CHECK_THROWS_WITH_AS(j.dump(1, ' ', false, json::error_handler_t::strict), "[json.exception.type_error.316] invalid UTF-8 byte at index 2: 0xA9", json::type_error&);
-            CHECK_THROWS_WITH_AS(utils::ignore_return_value(j.dump(1, ' ', false, json::error_handler_t::strict)), "[json.exception.type_error.316] invalid UTF-8 byte at index 2: 0xA9", json::type_error&);
             CHECK(j.dump(-1, ' ', false, json::error_handler_t::ignore) == "\"äü\"");
             CHECK(j.dump(-1, ' ', false, json::error_handler_t::replace) == "\"ä\xEF\xBF\xBDü\"");
             CHECK(j.dump(-1, ' ', true, json::error_handler_t::replace) == "\"\\u00e4\\ufffd\\u00fc\"");
@@ -98,9 +95,8 @@ TEST_CASE("serialization")
         {
             const json j = "123\xC2";
 
-            // dump() is nodiscard; the exception is thrown by dump() itself before it would return
+            CHECK_THROWS_WITH_AS(j.dump(), "[json.exception.type_error.316] incomplete UTF-8 string; last byte: 0xC2", json::type_error&);
-            CHECK_THROWS_WITH_AS(utils::ignore_return_value(j.dump()), "[json.exception.type_error.316] incomplete UTF-8 string; last byte: 0xC2", json::type_error&);
+            CHECK_THROWS_AS(j.dump(1, ' ', false, json::error_handler_t::strict), json::type_error&);
-            CHECK_THROWS_AS(utils::ignore_return_value(j.dump(1, ' ', false, json::error_handler_t::strict)), json::type_error&);
             CHECK(j.dump(-1, ' ', false, json::error_handler_t::ignore) == "\"123\"");
             CHECK(j.dump(-1, ' ', false, json::error_handler_t::replace) == "\"123\xEF\xBF\xBD\"");
             CHECK(j.dump(-1, ' ', true, json::error_handler_t::replace) == "\"123\\ufffd\"");
@@ -110,9 +106,8 @@ TEST_CASE("serialization")
         {
             const json j = "123\xF1\xB0\x34\x35\x36";
 
-            // dump() is nodiscard; the exception is thrown by dump() itself before it would return
+            CHECK_THROWS_WITH_AS(j.dump(), "[json.exception.type_error.316] invalid UTF-8 byte at index 5: 0x34", json::type_error&);
-            CHECK_THROWS_WITH_AS(utils::ignore_return_value(j.dump()), "[json.exception.type_error.316] invalid UTF-8 byte at index 5: 0x34", json::type_error&);
+            CHECK_THROWS_AS(j.dump(1, ' ', false, json::error_handler_t::strict), json::type_error&);
-            CHECK_THROWS_AS(utils::ignore_return_value(j.dump(1, ' ', false, json::error_handler_t::strict)), json::type_error&);
             CHECK(j.dump(-1, ' ', false, json::error_handler_t::ignore) == "\"123456\"");
             CHECK(j.dump(-1, ' ', false, json::error_handler_t::replace) == "\"123\xEF\xBF\xBD\x34\x35\x36\"");
             CHECK(j.dump(-1, ' ', true, json::error_handler_t::replace) == "\"123\\ufffd456\"");

tests/src/unit-unicode1.cpp

@@ -17,7 +17,6 @@ using nlohmann::json;
 #include <sstream>
 #include <iomanip>
 #include "make_test_data_available.hpp"
-#include "test_utils.hpp"
 
 TEST_CASE("Unicode (1/5)" * doctest::skip())
 {
@@ -241,8 +240,7 @@ void roundtrip(bool success_expected, const std::string& s)
     if (success_expected)
     {
         // serialization succeeds
-        // dump() is nodiscard; this only checks that dumping does not throw
+        CHECK_NOTHROW(j.dump());
-        CHECK_NOTHROW(utils::ignore_return_value(j.dump()));
 
         // exclude parse test for U+0000
         if (s[0] != '\0')
@@ -261,8 +259,7 @@ void roundtrip(bool success_expected, const std::string& s)
     else
     {
         // serialization fails
-        // dump() is nodiscard; the exception is thrown by dump() itself before it would return
+        CHECK_THROWS_AS(j.dump(), json::type_error&);
-        CHECK_THROWS_AS(utils::ignore_return_value(j.dump()), json::type_error&);
 
         // parsing JSON text fails
         CHECK_THROWS_AS(_ = json::parse(ps), json::parse_error&);

tests/src/unit-unicode2.cpp

@@ -19,7 +19,6 @@ using nlohmann::json;
 #include <iostream>
 #include <iomanip>
 #include "make_test_data_available.hpp"
-#include "test_utils.hpp"
 
 // this test suite uses static variables with non-trivial destructors
 DOCTEST_CLANG_SUPPRESS_WARNING_PUSH
@@ -98,8 +97,7 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
     else
     {
         // strict mode must throw if success is not expected
-        // dump() is nodiscard; the exception is thrown by dump() itself before it would return
+        CHECK_THROWS_AS(j.dump(), json::type_error&);
-        CHECK_THROWS_AS(utils::ignore_return_value(j.dump()), json::type_error&);
         // ignore and replace must create different dumps
         CHECK(s_ignored != s_replaced);
 

tests/src/unit-unicode3.cpp

@@ -19,7 +19,6 @@ using nlohmann::json;
 #include <iostream>
 #include <iomanip>
 #include "make_test_data_available.hpp"
-#include "test_utils.hpp"
 
 // this test suite uses static variables with non-trivial destructors
 DOCTEST_CLANG_SUPPRESS_WARNING_PUSH
@@ -98,8 +97,7 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
     else
     {
         // strict mode must throw if success is not expected
-        // dump() is nodiscard; the exception is thrown by dump() itself before it would return
+        CHECK_THROWS_AS(j.dump(), json::type_error&);
-        CHECK_THROWS_AS(utils::ignore_return_value(j.dump()), json::type_error&);
         // ignore and replace must create different dumps
         CHECK(s_ignored != s_replaced);
 

tests/src/unit-unicode4.cpp

@@ -19,7 +19,6 @@ using nlohmann::json;
 #include <iostream>
 #include <iomanip>
 #include "make_test_data_available.hpp"
-#include "test_utils.hpp"
 
 // this test suite uses static variables with non-trivial destructors
 DOCTEST_CLANG_SUPPRESS_WARNING_PUSH
@@ -98,8 +97,7 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
     else
     {
         // strict mode must throw if success is not expected
-        // dump() is nodiscard; the exception is thrown by dump() itself before it would return
+        CHECK_THROWS_AS(j.dump(), json::type_error&);
-        CHECK_THROWS_AS(utils::ignore_return_value(j.dump()), json::type_error&);
         // ignore and replace must create different dumps
         CHECK(s_ignored != s_replaced);
 

tests/src/unit-unicode5.cpp

@@ -19,7 +19,6 @@ using nlohmann::json;
 #include <iostream>
 #include <iomanip>
 #include "make_test_data_available.hpp"
-#include "test_utils.hpp"
 
 // this test suite uses static variables with non-trivial destructors
 DOCTEST_CLANG_SUPPRESS_WARNING_PUSH
@@ -98,8 +97,7 @@ void check_utf8dump(bool success_expected, int byte1, int byte2 = -1, int byte3
     else
     {
         // strict mode must throw if success is not expected
-        // dump() is nodiscard; the exception is thrown by dump() itself before it would return
+        CHECK_THROWS_AS(j.dump(), json::type_error&);
-        CHECK_THROWS_AS(utils::ignore_return_value(j.dump()), json::type_error&);
         // ignore and replace must create different dumps
         CHECK(s_ignored != s_replaced);