⚗️ use proper header for filesystem

.clang-tidy

@@ -30,6 +30,7 @@ Checks: '*,
          -llvmlibc-*,
          -misc-no-recursion,
          -misc-non-private-member-variables-in-classes,
+         -modernize-use-nodiscard,
          -modernize-use-trailing-return-type,
          -readability-function-size,
          -readability-function-cognitive-complexity,

include/nlohmann/detail/conversions/from_json.hpp

@@ -20,7 +20,19 @@
 #include <nlohmann/detail/value_t.hpp>
 
 #ifdef JSON_HAS_CPP_17
-    #include <filesystem>
+#if JSON_STD_FILESYSTEM_EXPERIMENTAL
+#include <experimental/filesystem>
+namespace nlohmann::detail
+{
+namespace std_fs = std::experimental::filesystem;
+}
+#else
+#include <filesystem>
+namespace nlohmann::detail
+{
+namespace std_fs = std::filesystem;
+}
+#endif
 #endif
 
 namespace nlohmann
@@ -450,7 +462,7 @@ void from_json(const BasicJsonType& j, std::unordered_map<Key, Value, Hash, KeyE
 
 #ifdef JSON_HAS_CPP_17
 template<typename BasicJsonType>
-void from_json(const BasicJsonType& j, std::filesystem::path& p)
+void from_json(const BasicJsonType& j, std_fs::path& p)
 {
     if (JSON_HEDLEY_UNLIKELY(!j.is_string()))
     {

include/nlohmann/detail/conversions/to_json.hpp

@@ -16,7 +16,19 @@
 #include <nlohmann/detail/value_t.hpp>
 
 #ifdef JSON_HAS_CPP_17
-    #include <filesystem>
+#if JSON_STD_FILESYSTEM_EXPERIMENTAL
+#include <experimental/filesystem>
+namespace nlohmann::detail
+{
+namespace std_fs = std::experimental::filesystem;
+}
+#else
+#include <filesystem>
+namespace nlohmann::detail
+{
+namespace std_fs = std::filesystem;
+}
+#endif
 #endif
 
 namespace nlohmann
@@ -393,7 +405,7 @@ void to_json(BasicJsonType& j, const T& t)
 
 #ifdef JSON_HAS_CPP_17
 template<typename BasicJsonType>
-void to_json(BasicJsonType& j, const std::filesystem::path& p)
+void to_json(BasicJsonType& j, const std_fs::path& p)
 {
     j = p.string();
 }

include/nlohmann/detail/macro_scope.hpp

@@ -37,6 +37,23 @@
     #define JSON_HAS_CPP_11
 #endif
 
+#ifdef JSON_HAS_CPP_17
+    // set JSON_STD_FILESYSTEM_EXPERIMENTAL to 1 if <experimental/filesystem> should be taken instead of <filesystem>
+    #if defined(__cpp_lib_filesystem)
+        #define JSON_STD_FILESYSTEM_EXPERIMENTAL 0
+    #elif defined(__cpp_lib_experimental_filesystem)
+        #define JSON_STD_FILESYSTEM_EXPERIMENTAL 1
+    #elif !defined(__has_include)
+        #define JSON_STD_FILESYSTEM_EXPERIMENTAL 1
+    #elif __has_include(<filesystem>)
+        #define JSON_STD_FILESYSTEM_EXPERIMENTAL 0
+    #elif __has_include(<experimental/filesystem>)
+        #define JSON_STD_FILESYSTEM_EXPERIMENTAL 1
+    #else
+        #define JSON_STD_FILESYSTEM_EXPERIMENTAL 0
+    #endif
+#endif
+
 // disable documentation warnings on clang
 #if defined(__clang__)
     #pragma clang diagnostic push

include/nlohmann/detail/macro_unscope.hpp

@@ -16,6 +16,7 @@
 #undef JSON_HAS_CPP_14
 #undef JSON_HAS_CPP_17
 #undef JSON_HAS_CPP_20
+#undef JSON_STD_FILESYSTEM_EXPERIMENTAL
 #undef NLOHMANN_BASIC_JSON_TPL_DECLARATION
 #undef NLOHMANN_BASIC_JSON_TPL
 #undef JSON_EXPLICIT

single_include/nlohmann/json.hpp

@@ -2325,6 +2325,23 @@ using is_detected_convertible =
     #define JSON_HAS_CPP_11
 #endif
 
+#ifdef JSON_HAS_CPP_17
+    // set JSON_STD_FILESYSTEM_EXPERIMENTAL to 1 if <experimental/filesystem> should be taken instead of <filesystem>
+    #if defined(__cpp_lib_filesystem)
+        #define JSON_STD_FILESYSTEM_EXPERIMENTAL 0
+    #elif defined(__cpp_lib_experimental_filesystem)
+        #define JSON_STD_FILESYSTEM_EXPERIMENTAL 1
+    #elif !defined(__has_include)
+        #define JSON_STD_FILESYSTEM_EXPERIMENTAL 1
+    #elif __has_include(<filesystem>)
+        #define JSON_STD_FILESYSTEM_EXPERIMENTAL 0
+    #elif __has_include(<experimental/filesystem>)
+        #define JSON_STD_FILESYSTEM_EXPERIMENTAL 1
+    #else
+        #define JSON_STD_FILESYSTEM_EXPERIMENTAL 0
+    #endif
+#endif
+
 // disable documentation warnings on clang
 #if defined(__clang__)
     #pragma clang diagnostic push
@@ -3951,7 +3968,19 @@ T conditional_static_cast(U value)
 
 
 #ifdef JSON_HAS_CPP_17
-    #include <filesystem>
+#if JSON_STD_FILESYSTEM_EXPERIMENTAL
+#include <experimental/filesystem>
+namespace nlohmann::detail
+{
+namespace std_fs = std::experimental::filesystem;
+}
+#else
+#include <filesystem>
+namespace nlohmann::detail
+{
+namespace std_fs = std::filesystem;
+}
+#endif
 #endif
 
 namespace nlohmann
@@ -4381,7 +4410,7 @@ void from_json(const BasicJsonType& j, std::unordered_map<Key, Value, Hash, KeyE
 
 #ifdef JSON_HAS_CPP_17
 template<typename BasicJsonType>
-void from_json(const BasicJsonType& j, std::filesystem::path& p)
+void from_json(const BasicJsonType& j, std_fs::path& p)
 {
     if (JSON_HEDLEY_UNLIKELY(!j.is_string()))
     {
@@ -4627,7 +4656,19 @@ class tuple_element<N, ::nlohmann::detail::iteration_proxy_value<IteratorType >>
 
 
 #ifdef JSON_HAS_CPP_17
-    #include <filesystem>
+#if JSON_STD_FILESYSTEM_EXPERIMENTAL
+#include <experimental/filesystem>
+namespace nlohmann::detail
+{
+namespace std_fs = std::experimental::filesystem;
+}
+#else
+#include <filesystem>
+namespace nlohmann::detail
+{
+namespace std_fs = std::filesystem;
+}
+#endif
 #endif
 
 namespace nlohmann
@@ -5004,7 +5045,7 @@ void to_json(BasicJsonType& j, const T& t)
 
 #ifdef JSON_HAS_CPP_17
 template<typename BasicJsonType>
-void to_json(BasicJsonType& j, const std::filesystem::path& p)
+void to_json(BasicJsonType& j, const std_fs::path& p)
 {
     j = p.string();
 }
@@ -26591,6 +26632,7 @@ inline nlohmann::json::json_pointer operator "" _json_pointer(const char* s, std
 #undef JSON_HAS_CPP_14
 #undef JSON_HAS_CPP_17
 #undef JSON_HAS_CPP_20
+#undef JSON_STD_FILESYSTEM_EXPERIMENTAL
 #undef NLOHMANN_BASIC_JSON_TPL_DECLARATION
 #undef NLOHMANN_BASIC_JSON_TPL
 #undef JSON_EXPLICIT

test/src/unit-regression2.cpp

@@ -47,8 +47,20 @@ using ordered_json = nlohmann::ordered_json;
 #endif
 
 #ifdef JSON_HAS_CPP_17
-    #include <filesystem>
+#include <variant>
-    #include <variant>
+#if JSON_STD_FILESYSTEM_EXPERIMENTAL
+#include <experimental/filesystem>
+namespace nlohmann::detail
+{
+namespace std_fs = std::experimental::filesystem;
+}
+#else
+#include <filesystem>
+namespace nlohmann::detail
+{
+namespace std_fs = std::filesystem;
+}
+#endif
 #endif
 
 #ifdef JSON_HAS_CPP_20
@@ -731,10 +743,10 @@ TEST_CASE("regression tests 2")
 #ifdef JSON_HAS_CPP_17
     SECTION("issue #3070 - Version 3.10.3 breaks backward-compatibility with 3.10.2 ")
     {
-        std::filesystem::path text_path("/tmp/text.txt");
+        nlohmann::detail::std_fs::path text_path("/tmp/text.txt");
         json j(text_path);
 
-        const auto j_path = j.get<std::filesystem::path>();
+        const auto j_path = j.get<nlohmann::detail::std_fs::path>();
         CHECK(j_path == text_path);
     }
 #endif