Fix CI: include cycle, GCC 4.8 literal operator spacing, and global UDLs off in the JSON_NO_AUTOMATIC_UDLS test

- Suppress clang-tidy misc-header-include-cycle on the intentional mutual
  include of json.hpp and json_literals.hpp.
- Use operator"" _json with a space for GCC 4.8 in the test's detection
  aliases, as the header does.
- Only test the global literal operators when JSON_USE_GLOBAL_UDLS is on.

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

include/nlohmann/json.hpp

@@ -6569,6 +6569,7 @@ struct formatter<nlohmann::NLOHMANN_BASIC_JSON_TPL, char> // NOLINT(cert-dcl58-c
 // Define JSON_NO_AUTOMATIC_UDLS to include <nlohmann/json_literals.hpp> only
 // where needed.
 #ifndef JSON_NO_AUTOMATIC_UDLS
+    // NOLINTNEXTLINE(misc-header-include-cycle): json_literals.hpp includes this header
     #include <nlohmann/json_literals.hpp>
 #endif
 

include/nlohmann/json_literals.hpp

@@ -12,6 +12,7 @@
 #include <cstddef> // size_t
 #include <string> // string
 
+// NOLINTNEXTLINE(misc-header-include-cycle): json.hpp includes this header at its end
 #include <nlohmann/json.hpp>
 
 // This header is included at the end of <nlohmann/json.hpp> unless

single_include/nlohmann/json.hpp

@@ -32859,6 +32859,7 @@ struct formatter<nlohmann::NLOHMANN_BASIC_JSON_TPL, char> // NOLINT(cert-dcl58-c
 // Define JSON_NO_AUTOMATIC_UDLS to include <nlohmann/json_literals.hpp> only
 // where needed.
 #ifndef JSON_NO_AUTOMATIC_UDLS
+// NOLINTNEXTLINE(misc-header-include-cycle): json_literals.hpp includes this header
 // #include <nlohmann/json_literals.hpp>
 //     __ _____ _____ _____
 //  __|  |   __|     |   | |  JSON for Modern C++
@@ -32874,6 +32875,7 @@ struct formatter<nlohmann::NLOHMANN_BASIC_JSON_TPL, char> // NOLINT(cert-dcl58-c
 #include <cstddef> // size_t
 #include <string> // string
 
+// NOLINTNEXTLINE(misc-header-include-cycle): json.hpp includes this header at its end
 // #include <nlohmann/json.hpp>
 
 

single_include/nlohmann/json_literals.hpp

@@ -12,6 +12,7 @@
 #include <cstddef> // size_t
 #include <string> // string
 
+// NOLINTNEXTLINE(misc-header-include-cycle): json.hpp includes this header at its end
 #include <nlohmann/json.hpp>
 
 // This header is included at the end of <nlohmann/json.hpp> unless

tests/src/unit-no_automatic_udls.cpp

@@ -41,11 +41,20 @@ namespace
 // deferred to the point of instantiation, where it considers the declarations
 // visible from here (the global using-declarations of JSON_USE_GLOBAL_UDLS) plus
 // argument-dependent lookup (the literals in the library namespace).
-template<typename T>
-using json_udl_t = decltype(operator""_json(std::declval<T>(), std::size_t()));
+#if !defined(__GNUC__) || defined(__clang__) || __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 9)
+    template<typename T>
+    using json_udl_t = decltype(operator""_json(std::declval<T>(), std::size_t()));
 
-template<typename T>
-using json_pointer_udl_t = decltype(operator""_json_pointer(std::declval<T>(), std::size_t()));
+    template<typename T>
+    using json_pointer_udl_t = decltype(operator""_json_pointer(std::declval<T>(), std::size_t()));
+#else
+    // GCC 4.8 requires a space between "" and suffix
+    template<typename T>
+    using json_udl_t = decltype(operator"" _json(std::declval<T>(), std::size_t()));
+
+    template<typename T>
+    using json_pointer_udl_t = decltype(operator"" _json_pointer(std::declval<T>(), std::size_t()));
+#endif
 
 template<typename T>
 using has_json_udl = nlohmann::detail::is_detected<json_udl_t, T>;
@@ -83,11 +92,13 @@ TEST_CASE("JSON_NO_AUTOMATIC_UDLS")
 
 TEST_CASE("JSON_NO_AUTOMATIC_UDLS with <nlohmann/json_literals.hpp>")
 {
+#if !defined(JSON_USE_GLOBAL_UDLS) || JSON_USE_GLOBAL_UDLS
     SECTION("global namespace")
     {
         CHECK("[1,2]"_json == json({1, 2}));
         CHECK("/a/0"_json_pointer == json::json_pointer("/a/0"));
     }
+#endif
 
     SECTION("nlohmann::literals::json_literals")
     {