Make std::filesystem::path conversion to/from UTF-8 encoded string explicit.

Richard Musil · Richard Musil · commit a395539edd86 · 2025-01-26T20:40:45.000+01:00
Signed-off-by: Richard Musil &lt;risa2000x@gmail.com&gt;
diff --git a/include/nlohmann/detail/conversions/from_json.hpp b/include/nlohmann/detail/conversions/from_json.hpp
@@ -539,7 +539,12 @@ inline void from_json(const BasicJsonType& j, std_fs::path& p)
     {
         JSON_THROW(type_error::create(302, concat("type must be string, but is ", j.type_name()), &j));
     }
-    p = *j.template get_ptr<const typename BasicJsonType::string_t*>();
+    const auto& s = *j.template get_ptr<const typename BasicJsonType::string_t*>();
+#ifdef JSON_HAS_CPP_20
+    p = std_fs::path(std::u8string_view(reinterpret_cast<const char8_t*>(s.data()), s.size()));
+#else
+    p = std_fs::u8path(s); // accepts UTF-8 encoded std::string in C++17, deprecated in C++20
+#endif
 }
 #endif
 
diff --git a/include/nlohmann/detail/conversions/to_json.hpp b/include/nlohmann/detail/conversions/to_json.hpp
@@ -443,7 +443,12 @@ inline void to_json(BasicJsonType& j, const T& t)
 template<typename BasicJsonType>
 inline void to_json(BasicJsonType& j, const std_fs::path& p)
 {
-    j = p.string();
+#ifdef JSON_HAS_CPP_20
+    const std::u8string s = p.u8string();
+    j = std::string(s.begin(), s.end());
+#else
+    j = p.u8string(); // returns std::string in C++17
+#endif
 }
 #endif
 
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
@@ -5319,7 +5319,12 @@ inline void from_json(const BasicJsonType& j, std_fs::path& p)
     {
         JSON_THROW(type_error::create(302, concat("type must be string, but is ", j.type_name()), &j));
     }
-    p = *j.template get_ptr<const typename BasicJsonType::string_t*>();
+    const auto& s = *j.template get_ptr<const typename BasicJsonType::string_t*>();
+#ifdef JSON_HAS_CPP_20
+    p = std_fs::path(std::u8string_view(reinterpret_cast<const char8_t*>(s.data()), s.size()));
+#else
+    p = std_fs::u8path(s); // accepts UTF-8 encoded std::string in C++17, deprecated in C++20
+#endif
 }
 #endif
 
@@ -6080,7 +6085,12 @@ inline void to_json(BasicJsonType& j, const T& t)
 template<typename BasicJsonType>
 inline void to_json(BasicJsonType& j, const std_fs::path& p)
 {
-    j = p.string();
+#ifdef JSON_HAS_CPP_20
+    const std::u8string s = p.u8string();
+    j = std::string(s.begin(), s.end());
+#else
+    j = p.u8string(); // returns std::string in C++17
+#endif
 }
 #endif
 
diff --git a/tests/src/unit-conversions.cpp b/tests/src/unit-conversions.cpp

Original file line number	Diff line number	Diff line change
`@@ -539,7 +539,12 @@ inline void from_json(const BasicJsonType& j, std_fs::path& p)`
`539`	`539`	`{`
`540`	`540`	`JSON_THROW(type_error::create(302, concat("type must be string, but is ", j.type_name()), &j));`
`541`	`541`	`}`
`542`		`- p = j.template get_ptr<const typename BasicJsonType::string_t>();`
	`542`	`+ const auto& s = j.template get_ptr<const typename BasicJsonType::string_t>();`
	`543`	`+#ifdef JSON_HAS_CPP_20`
	`544`	`+ p = std_fs::path(std::u8string_view(reinterpret_cast<const char8_t*>(s.data()), s.size()));`
	`545`	`+#else`
	`546`	`+ p = std_fs::u8path(s); // accepts UTF-8 encoded std::string in C++17, deprecated in C++20`
	`547`	`+#endif`
`543`	`548`	`}`
`544`	`549`	`#endif`
`545`	`550`
Original file line number	Diff line number	Diff line change
`@@ -443,7 +443,12 @@ inline void to_json(BasicJsonType& j, const T& t)`
`443`	`443`	`template<typename BasicJsonType>`
`444`	`444`	`inline void to_json(BasicJsonType& j, const std_fs::path& p)`
`445`	`445`	`{`
`446`		`- j = p.string();`
	`446`	`+#ifdef JSON_HAS_CPP_20`
	`447`	`+ const std::u8string s = p.u8string();`
	`448`	`+ j = std::string(s.begin(), s.end());`
	`449`	`+#else`
	`450`	`+ j = p.u8string(); // returns std::string in C++17`
	`451`	`+#endif`
`447`	`452`	`}`
`448`	`453`	`#endif`
`449`	`454`
Original file line number	Diff line number	Diff line change
`@@ -5319,7 +5319,12 @@ inline void from_json(const BasicJsonType& j, std_fs::path& p)`
`5319`	`5319`	`{`
`5320`	`5320`	`JSON_THROW(type_error::create(302, concat("type must be string, but is ", j.type_name()), &j));`
`5321`	`5321`	`}`
`5322`		`- p = j.template get_ptr<const typename BasicJsonType::string_t>();`
	`5322`	`+ const auto& s = j.template get_ptr<const typename BasicJsonType::string_t>();`
	`5323`	`+#ifdef JSON_HAS_CPP_20`
	`5324`	`+ p = std_fs::path(std::u8string_view(reinterpret_cast<const char8_t*>(s.data()), s.size()));`
	`5325`	`+#else`
	`5326`	`+ p = std_fs::u8path(s); // accepts UTF-8 encoded std::string in C++17, deprecated in C++20`
	`5327`	`+#endif`
`5323`	`5328`	`}`
`5324`	`5329`	`#endif`
`5325`	`5330`
`@@ -6080,7 +6085,12 @@ inline void to_json(BasicJsonType& j, const T& t)`
`6080`	`6085`	`template<typename BasicJsonType>`
`6081`	`6086`	`inline void to_json(BasicJsonType& j, const std_fs::path& p)`
`6082`	`6087`	`{`
`6083`		`- j = p.string();`
	`6088`	`+#ifdef JSON_HAS_CPP_20`
	`6089`	`+ const std::u8string s = p.u8string();`
	`6090`	`+ j = std::string(s.begin(), s.end());`
	`6091`	`+#else`
	`6092`	`+ j = p.u8string(); // returns std::string in C++17`
	`6093`	`+#endif`
`6084`	`6094`	`}`
`6085`	`6095`	`#endif`
`6086`	`6096`