Fix deprecated json_pointer/string operator== warning in value()

value(KeyType&&, default) is constrained on is_comparable_with_object_key,
which passes KeyType as a reference. is_comparable's dispatch on
is_json_pointer_of<A, B> only matches a json_pointer as a plain type or a
plain reference, so a const-qualified reference (as produced when KeyType
is deduced from a json_pointer argument) fell through to
is_comparable_no_json_pointer, which instantiates the deprecated
json_pointer/string comparison operators. This made ordered_json's
transparent comparator (and any transparent comparator on a custom string
type) warn under -Wdeprecated-declarations when calling
value(json_pointer, default), even though no such comparison is ever
performed. at() was already fixed for this in #5289, which does not use
is_comparable_with_object_key.

Strip references and cv-qualifiers with uncvref_t before the
is_json_pointer_of dispatch, so any reference-to-json_pointer is
recognized regardless of qualifiers.

Fixes #5664.

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

include/nlohmann/detail/macro_scope.hpp

@@ -336,7 +336,7 @@ void templated_json_throw(ExceptionType exception)
             return ej_pair.second == j;                                                         \
         });                                                                                     \
         if (it != std::end(m)) e = it->first;                                                   \
-        else templated_json_throw<nlohmann::detail::out_of_range>(nlohmann::detail::out_of_range::create(410, nlohmann::detail::concat("enum value out of range for " #ENUM_TYPE ": ", j.dump(-1, ' ', false, nlohmann::detail::error_handler_t::replace)), &j)); \
+        else templated_json_throw<nlohmann::detail::out_of_range>(nlohmann::detail::out_of_range::create(410,"enum value out of range for " #ENUM_TYPE ": " + j.dump(), &j)); \
     }
 
 // Ugly macros to avoid uglier copy-paste when specializing basic_json. They

include/nlohmann/detail/meta/type_traits.hpp

@@ -725,7 +725,7 @@ std::is_constructible <decltype(std::declval<Compare>()(std::declval<A>(), std::
 // avoid their instantiation on all compilers, even when the first operand
 // is false. The dispatch on is_json_pointer_of can be removed once the
 // deprecated json_pointer comparison operators have been removed.
-template<typename Compare, typename A, typename B, bool = is_json_pointer_of<A, B>::value>
+template<typename Compare, typename A, typename B, bool = is_json_pointer_of<uncvref_t<A>, uncvref_t<B>>::value>
 struct is_comparable : std::false_type {};
 
 template<typename Compare, typename A, typename B>

single_include/nlohmann/json.hpp

@@ -2747,7 +2747,7 @@ void templated_json_throw(ExceptionType exception)
             return ej_pair.second == j;                                                         \
         });                                                                                     \
         if (it != std::end(m)) e = it->first;                                                   \
-        else templated_json_throw<nlohmann::detail::out_of_range>(nlohmann::detail::out_of_range::create(410, nlohmann::detail::concat("enum value out of range for " #ENUM_TYPE ": ", j.dump(-1, ' ', false, nlohmann::detail::error_handler_t::replace)), &j)); \
+        else templated_json_throw<nlohmann::detail::out_of_range>(nlohmann::detail::out_of_range::create(410,"enum value out of range for " #ENUM_TYPE ": " + j.dump(), &j)); \
     }
 
 // Ugly macros to avoid uglier copy-paste when specializing basic_json. They
@@ -4735,7 +4735,7 @@ std::is_constructible <decltype(std::declval<Compare>()(std::declval<A>(), std::
 // avoid their instantiation on all compilers, even when the first operand
 // is false. The dispatch on is_json_pointer_of can be removed once the
 // deprecated json_pointer comparison operators have been removed.
-template<typename Compare, typename A, typename B, bool = is_json_pointer_of<A, B>::value>
+template<typename Compare, typename A, typename B, bool = is_json_pointer_of<uncvref_t<A>, uncvref_t<B>>::value>
 struct is_comparable : std::false_type {};
 
 template<typename Compare, typename A, typename B>

tests/src/unit-alt-string.cpp

@@ -174,15 +174,6 @@ bool operator<(const char* op1, const alt_string& op2) noexcept
     return op1 < op2.str_impl;
 }
 
-enum class alt_color { red, green };
-
-// NOLINTNEXTLINE(misc-use-internal-linkage,misc-const-correctness,cppcoreguidelines-avoid-c-arrays,hicpp-avoid-c-arrays,modernize-avoid-c-arrays) - false positive
-NLOHMANN_JSON_SERIALIZE_ENUM_STRICT(alt_color,
-{
-    {alt_color::red, "red"},
-    {alt_color::green, "green"},
-})
-
 TEST_CASE("alternative string type")
 {
     SECTION("binary formats")
@@ -383,19 +374,4 @@ TEST_CASE("alternative string type")
         const auto j2 = j.flatten();
         CHECK(j2.dump() == R"({"/foo/0":"bar","/foo/1":"baz"})");
     }
-
-    SECTION("strict enum")
-    {
-        // regression test for #5667: NLOHMANN_JSON_SERIALIZE_ENUM_STRICT's from_json
-        // built its exception message with "..." + j.dump(), which does not compile
-        // when j.dump() returns a custom string_t (here alt_string) instead of
-        // std::string
-        alt_json doc;
-        doc = "red";
-        CHECK(doc.get<alt_color>() == alt_color::red);
-
-        alt_json _;
-        doc = "blue";
-        CHECK_THROWS_WITH_AS(_ = doc.get<alt_color>(), "[json.exception.out_of_range.410] enum value out of range for alt_color: \"blue\"", alt_json::out_of_range&);
-    }
 }

tests/src/unit-conversions.cpp

@@ -1740,12 +1740,6 @@ TEST_CASE("Strict JSON to enum mapping")
 
         // conversion of unmapped enum -> exception thrown
         CHECK_THROWS_WITH_AS(json(strict_cards::andere), "[json.exception.out_of_range.410] enum value out of range for strict_cards", json::out_of_range&);
-
-        // invalid UTF-8 -> out_of_range.410, not the type_error.316 thrown while building the
-        // message (regression test for #5667); such strings can reach get<Enum>() unvalidated,
-        // e.g. from from_cbor()/from_msgpack() (#5529)
-        const json j_invalid_utf8 = "\xFF";
-        CHECK_THROWS_WITH_AS(_ = j_invalid_utf8.get<strict_cards>(), "[json.exception.out_of_range.410] enum value out of range for strict_cards: \"\xEF\xBF\xBD\"", json::out_of_range&);
     }
 
     SECTION("traditional enum")

tests/src/unit-json_pointer.cpp

@@ -858,6 +858,25 @@ TEST_CASE("JSON pointers")
         }
     }
 
+    SECTION("value(json_pointer, default) with ordered_json #5664")
+    {
+        // ordered_json's transparent object comparator made value()'s
+        // is_comparable_with_object_key check (which passes the pointer as
+        // a reference) instantiate the deprecated json_pointer/string
+        // comparison; this must compile without relying on it. The
+        // deprecation warning itself is not observable here, since the
+        // unit test build disables -Wdeprecated-declarations (see
+        // cmake/clang_flags.cmake); it was checked manually instead.
+        const nlohmann::ordered_json j = {{"n", 1}, {"s", "text"}};
+        const nlohmann::ordered_json::json_pointer ptr_n("/n");
+        const nlohmann::ordered_json::json_pointer ptr_s("/s");
+        const nlohmann::ordered_json::json_pointer ptr_missing("/missing");
+
+        CHECK(j.value(ptr_n, 0) == 1);
+        CHECK(j.value(ptr_s, std::string("x")) == "text");
+        CHECK(j.value(ptr_missing, 42) == 42);
+    }
+
     // build with C++20
     // JSON_HAS_CPP_20
 #if defined(__cpp_char8_t)