Use the guarded/direct export of header approach

Author: mikomikotaishi

.github/workflows/update-module-exports.yml

@@ -248,6 +248,16 @@ if(HTTPLIB_COMPILE)
 			$<BUILD_INTERFACE:${_httplib_build_includedir}/httplib.h>
 			$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}/httplib.h>
 	)
+	
+	# Add C++20 module support if requested
+	if(HTTPLIB_BUILD_MODULES)
+		target_sources(${PROJECT_NAME}
+			PUBLIC
+				FILE_SET CXX_MODULES FILES
+					"${_httplib_build_includedir}/httplib.cppm"
+		)
+	endif()
+	
 	set_target_properties(${PROJECT_NAME}
 		PROPERTIES
 			VERSION ${${PROJECT_NAME}_VERSION}
@@ -264,8 +274,12 @@ endif()
 # Only useful if building in-tree, versus using it from an installation.
 add_library(${PROJECT_NAME}::${PROJECT_NAME} ALIAS ${PROJECT_NAME})
 
-# Require C++11
-target_compile_features(${PROJECT_NAME} ${_INTERFACE_OR_PUBLIC} cxx_std_11)
+# Require C++11, or C++20 if modules are enabled
+if(HTTPLIB_BUILD_MODULES)
+	target_compile_features(${PROJECT_NAME} ${_INTERFACE_OR_PUBLIC} cxx_std_20)
+else()
+	target_compile_features(${PROJECT_NAME} ${_INTERFACE_OR_PUBLIC} cxx_std_11)
+endif()
 
 target_include_directories(${PROJECT_NAME} SYSTEM ${_INTERFACE_OR_PUBLIC}
 	$<BUILD_INTERFACE:${_httplib_build_includedir}>
@@ -337,7 +351,11 @@ if(HTTPLIB_INSTALL)
 	# Creates the export httplibTargets.cmake
 	# This is strictly what holds compilation requirements
 	# and linkage information (doesn't find deps though).
-	install(TARGETS ${PROJECT_NAME} EXPORT httplibTargets)
+	if(HTTPLIB_BUILD_MODULES)
+		install(TARGETS ${PROJECT_NAME} EXPORT httplibTargets FILE_SET CXX_MODULES DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}/httplib/modules CXX_MODULES_BMI DESTINATION ${CMAKE_INSTALL_LIBDIR}/httplib/modules)
+	else()
+		install(TARGETS ${PROJECT_NAME} EXPORT httplibTargets)
+	endif()
 
 	install(FILES "${_httplib_build_includedir}/httplib.h" TYPE INCLUDE)
 
@@ -366,14 +384,13 @@ if(HTTPLIB_INSTALL)
 	include(CPack)
 endif()
 
-if(HTTPLIB_TEST)
-	include(CTest)
-	add_subdirectory(test)
-endif()
-
 if(HTTPLIB_BUILD_MODULES)
 	if(NOT HTTPLIB_COMPILE)
 		message(FATAL_ERROR "HTTPLIB_BUILD_MODULES requires HTTPLIB_COMPILE to be ON.")
 	endif()
-	add_subdirectory(modules)
+endif()
+
+if(HTTPLIB_TEST)
+	include(CTest)
+	add_subdirectory(test)
 endif()

CMakeLists.txt

@@ -1275,43 +1275,6 @@ $ ./split.py
 Wrote out/httplib.h and out/httplib.cc
 ```
 
-Build C++ Modules
------------------
-
-If using CMake, it is possible to build this as a C++20 module using the `HTTPLIB_BUILD_MODULES` option (which requires `HTTPLIB_COMPILE` to be enabled).
-
-#### Server (Multi-threaded)
-```cpp
-import httplib;
-
-using httplib::Request;
-using httplib::Response;
-using httplib::SSLServer;
-
-SSLServer svr;
-
-svr.Get("/hi", []([[maybe_unused]] const Request& req, Response& res) -> void {
-  res.set_content("Hello World!", "text/plain");
-});
-
-svr.listen("0.0.0.0", 8080);
-```
-
-#### Client
-```cpp
-import httplib;
-
-using httplib::Client;
-using httplib::Result;
-
-Client cli("https://yhirose.github.io");
-
-if (Result res = cli.Get("/hi")) {
-  res->status;
-  res->body;
-}
-```
-
 Dockerfile for Static HTTP Server
 ---------------------------------