From 11cc676142d9ca85cc40a60330ed1b081c3afc6d Mon Sep 17 00:00:00 2001
From: Bander <66913005+banderzhm@users.noreply.github.com>
Date: Fri, 24 Oct 2025 17:34:11 +0800
Subject: [PATCH] Improve MSVC C++ modules compatibility for nlohmann_json
 (#4952)

* Improve MSVC C++ modules compatibility for nlohmann_json

- Keep complete module interface with all exports
- Export all standard types: json, basic_json, adl_serializer, json_pointer, ordered_json, ordered_map
- Export detail namespace symbols for advanced usage
- Ensure compatibility with MSVC C++20/23 modules
- Maintain full functionality without breaking changes

Signed-off-by: yudaichen <250074249@qq.com>

* Add C++20 module Windows CI test and fix file ending

- Add ci_module_cpp20 job to Windows workflow to verify module support with MSVC

- Add missing newline at end of json.cppm file

Signed-off-by: yudaichen <250074249@qq.com>

---------

Signed-off-by: yudaichen <250074249@qq.com>
---
 .github/workflows/windows.yml | 10 ++++++++++
 src/modules/json.cppm         | 18 ++++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/.github/workflows/windows.yml b/.github/workflows/windows.yml
index cb78c9294..229de56da 100644
--- a/.github/workflows/windows.yml
+++ b/.github/workflows/windows.yml
@@ -112,3 +112,13 @@ jobs:
         run: cmake --build build --config Debug --parallel 10
       - name: Test
         run: cd build ; ctest -j 10 -C Debug --exclude-regex "test-unicode" --output-on-failure
+
+  ci_module_cpp20:
+    runs-on: windows-latest
+    steps:
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+      - name: Run CMake (Debug)
+        run: cmake -S . -B build -G "Visual Studio 17 2022" -DJSON_CI=ON -DCMAKE_CXX_FLAGS="/permissive- /std:c++latest /utf-8 /W4 /WX"
+      - name: Build
+        run: cmake --build build --config Debug --target ci_module_cpp20
+        
\ No newline at end of file
diff --git a/src/modules/json.cppm b/src/modules/json.cppm
index 5f55acc2b..623d8cb81 100644
--- a/src/modules/json.cppm
+++ b/src/modules/json.cppm
@@ -12,3 +12,21 @@ export namespace nlohmann {
     using ::nlohmann::ordered_json;
     using ::nlohmann::ordered_map;
 }  // namespace nlohmann
+
+NLOHMANN_JSON_NAMESPACE_BEGIN
+
+namespace detail
+{
+    export using NLOHMANN_JSON_NAMESPACE::detail::json_sax_dom_callback_parser;
+    export using NLOHMANN_JSON_NAMESPACE::detail::unknown_size;
+} // namespace detail
+
+export using NLOHMANN_JSON_NAMESPACE::adl_serializer;
+export using NLOHMANN_JSON_NAMESPACE::basic_json;
+export using NLOHMANN_JSON_NAMESPACE::json;
+export using NLOHMANN_JSON_NAMESPACE::json_pointer;
+export using NLOHMANN_JSON_NAMESPACE::ordered_json;
+export using NLOHMANN_JSON_NAMESPACE::ordered_map;
+export using NLOHMANN_JSON_NAMESPACE::to_string;
+
+NLOHMANN_JSON_NAMESPACE_END