♻️ overwork std specializations

include/nlohmann/json.hpp

@@ -4707,20 +4707,16 @@ std::string to_string(const NLOHMANN_BASIC_JSON_TPL& j)
 // nonmember support //
 ///////////////////////
 
-// specialization of std::swap, and std::hash
-namespace std
-{
-
 /// hash value for JSON objects
-template<>
+template<typename BasicJsonType>
-struct hash<nlohmann::json>
+struct std::hash
 {
     /*!
     @brief return a hash value for a JSON object
 
-    @since version 1.0.0
+    @since version 1.0.0, extended for arbitrary basic_json types in 3.10.5.
     */
-    std::size_t operator()(const nlohmann::json& j) const
+    std::size_t operator()(const BasicJsonType& j) const
     {
         return nlohmann::detail::hash(j);
     }
@@ -4730,7 +4726,7 @@ struct hash<nlohmann::json>
 /// @note: do not remove the space after '<',
 ///        see https://github.com/nlohmann/json/pull/679
 template<>
-struct less<::nlohmann::detail::value_t>
+struct std::less< ::nlohmann::detail::value_t>
 {
     /*!
     @brief compare two value_t enum values
@@ -4746,6 +4742,9 @@ struct less<::nlohmann::detail::value_t>
 // C++20 prohibit function specialization in the std namespace.
 #ifndef JSON_HAS_CPP_20
 
+namespace std
+{
+
 /*!
 @brief exchanges the values of two JSON objects
 
@@ -4760,9 +4759,9 @@ inline void swap<nlohmann::json>(nlohmann::json& j1, nlohmann::json& j2) noexcep
     j1.swap(j2);
 }
 
-#endif
+// namespace std
 
-} // namespace std
+#endif
 
 /// @brief user-defined string literal for JSON values
 /// @sa https://json.nlohmann.me/api/basic_json/operator_literal_json/

single_include/nlohmann/json.hpp

@@ -22208,20 +22208,16 @@ std::string to_string(const NLOHMANN_BASIC_JSON_TPL& j)
 // nonmember support //
 ///////////////////////
 
-// specialization of std::swap, and std::hash
-namespace std
-{
-
 /// hash value for JSON objects
-template<>
+template<typename BasicJsonType>
-struct hash<nlohmann::json>
+struct std::hash
 {
     /*!
     @brief return a hash value for a JSON object
 
-    @since version 1.0.0
+    @since version 1.0.0, extended for arbitrary basic_json types in 3.10.5.
     */
-    std::size_t operator()(const nlohmann::json& j) const
+    std::size_t operator()(const BasicJsonType& j) const
     {
         return nlohmann::detail::hash(j);
     }
@@ -22231,7 +22227,7 @@ struct hash<nlohmann::json>
 /// @note: do not remove the space after '<',
 ///        see https://github.com/nlohmann/json/pull/679
 template<>
-struct less<::nlohmann::detail::value_t>
+struct std::less< ::nlohmann::detail::value_t>
 {
     /*!
     @brief compare two value_t enum values
@@ -22247,6 +22243,9 @@ struct less<::nlohmann::detail::value_t>
 // C++20 prohibit function specialization in the std namespace.
 #ifndef JSON_HAS_CPP_20
 
+namespace std
+{
+
 /*!
 @brief exchanges the values of two JSON objects
 
@@ -22261,9 +22260,9 @@ inline void swap<nlohmann::json>(nlohmann::json& j1, nlohmann::json& j2) noexcep
     j1.swap(j2);
 }
 
-#endif
+// namespace std
 
-} // namespace std
+#endif
 
 /// @brief user-defined string literal for JSON values
 /// @sa https://json.nlohmann.me/api/basic_json/operator_literal_json/

test/src/unit-hash.cpp

@@ -31,10 +31,11 @@ SOFTWARE.
 
 #include <nlohmann/json.hpp>
 using json = nlohmann::json;
+using ordered_json = nlohmann::ordered_json;
 
 #include <set>
 
-TEST_CASE("hash")
+TEST_CASE("hash<nlohmann::json>")
 {
     // Collect hashes for different JSON values and make sure that they are distinct
     // We cannot compare against fixed values, because the implementation of
@@ -82,3 +83,52 @@ TEST_CASE("hash")
 
     CHECK(hashes.size() == 21);
 }
+
+TEST_CASE("hash<nlohmann::ordered_json>")
+{
+    // Collect hashes for different JSON values and make sure that they are distinct
+    // We cannot compare against fixed values, because the implementation of
+    // std::hash may differ between compilers.
+
+    std::set<std::size_t> hashes;
+
+    // null
+    hashes.insert(std::hash<ordered_json> {}(ordered_json(nullptr)));
+
+    // boolean
+    hashes.insert(std::hash<ordered_json> {}(ordered_json(true)));
+    hashes.insert(std::hash<ordered_json> {}(ordered_json(false)));
+
+    // string
+    hashes.insert(std::hash<ordered_json> {}(ordered_json("")));
+    hashes.insert(std::hash<ordered_json> {}(ordered_json("foo")));
+
+    // number
+    hashes.insert(std::hash<ordered_json> {}(ordered_json(0)));
+    hashes.insert(std::hash<ordered_json> {}(ordered_json(unsigned(0))));
+
+    hashes.insert(std::hash<ordered_json> {}(ordered_json(-1)));
+    hashes.insert(std::hash<ordered_json> {}(ordered_json(0.0)));
+    hashes.insert(std::hash<ordered_json> {}(ordered_json(42.23)));
+
+    // array
+    hashes.insert(std::hash<ordered_json> {}(ordered_json::array()));
+    hashes.insert(std::hash<ordered_json> {}(ordered_json::array({1, 2, 3})));
+
+    // object
+    hashes.insert(std::hash<ordered_json> {}(ordered_json::object()));
+    hashes.insert(std::hash<ordered_json> {}(ordered_json::object({{"foo", "bar"}})));
+
+    // binary
+    hashes.insert(std::hash<ordered_json> {}(ordered_json::binary({})));
+    hashes.insert(std::hash<ordered_json> {}(ordered_json::binary({}, 0)));
+    hashes.insert(std::hash<ordered_json> {}(ordered_json::binary({}, 42)));
+    hashes.insert(std::hash<ordered_json> {}(ordered_json::binary({1, 2, 3})));
+    hashes.insert(std::hash<ordered_json> {}(ordered_json::binary({1, 2, 3}, 0)));
+    hashes.insert(std::hash<ordered_json> {}(ordered_json::binary({1, 2, 3}, 42)));
+
+    // discarded
+    hashes.insert(std::hash<ordered_json> {}(ordered_json(ordered_json::value_t::discarded)));
+
+    CHECK(hashes.size() == 21);
+}