Make std::filesystem::path conversion to/from UTF-8 encoded JSON stri…

…ng explicit. Signed-off-by: Richard Musil <[email protected]>
nlohmann · Jan 27, 2025 · 144f340 · 144f340
1 parent d0789e3
commit 144f340
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Showing 4 changed files with 49 additions and 4 deletions.
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
@@ -1658,6 +1658,31 @@ TEST_CASE("JSON to enum mapping")
 }
 
 #ifdef JSON_HAS_CPP_17
+#if JSON_HAS_FILESYSTEM || JSON_HAS_EXPERIMENTAL_FILESYSTEM
+TEST_CASE("std::filesystem::path")
+{
+    SECTION("ascii")
+    {
+        json const j_string = "Path";
+        auto p = j_string.template get<nlohmann::detail::std_fs::path>();
+        json const j_path = p;
+
+        CHECK(j_path.template get<std::string>() ==
+              j_string.template get<std::string>());
+    }
+
+    SECTION("utf-8")
+    {
+        json const j_string = "P\xc4\x9b\xc5\xa1ina";
+        auto p = j_string.template get<nlohmann::detail::std_fs::path>();
+        json const j_path = p;
+
+        CHECK(j_path.template get<std::string>() ==
+              j_string.template get<std::string>());
+    }
+}
+#endif
+
 #ifndef JSON_USE_IMPLICIT_CONVERSIONS
 TEST_CASE("std::optional")
 {