improving json dependency

Author: kadeslu

CMakeLists.txt

@@ -4,6 +4,10 @@ project(devdat VERSION 1.0.0 LANGUAGES CXX)
 # Options
 option(BUILD_TESTING "Build tests" ON)
 option(DEVDAT_USE_SYSTEM_JSON "Use system-installed nlohmann_json" OFF)
+# Add this to recognize the variable passed from superbuild
+if(DEFINED USE_SYSTEM_JSON)
+    set(DEVDAT_USE_SYSTEM_JSON ${USE_SYSTEM_JSON})
+endif()
 
 # Set C++ standard
 set(CMAKE_CXX_STANDARD 17)
@@ -24,21 +28,27 @@ endif()
 
 # Handle nlohmann_json dependency
 if(DEVDAT_USE_SYSTEM_JSON)
-    # Check if JSON_INCLUDE_DIR is provided by the superbuild
+    message(STATUS "Using system JSON (DEVDAT_USE_SYSTEM_JSON=${DEVDAT_USE_SYSTEM_JSON})")
+    
     if(DEFINED JSON_INCLUDE_DIR)
-        message(STATUS "Using JSON include directory provided by superbuild: ${JSON_INCLUDE_DIR}")
-        # Simple interface library to handle the include directory
-        add_library(json_interface INTERFACE)
-        target_include_directories(json_interface INTERFACE ${JSON_INCLUDE_DIR})
-        set(JSON_TARGET json_interface)
+        message(STATUS "JSON_INCLUDE_DIR is set to: ${JSON_INCLUDE_DIR}")
+        # Create a wrapper target that will be included in the export set
+        add_library(devdat_json_wrapper INTERFACE)
+        target_include_directories(devdat_json_wrapper INTERFACE 
+            $<BUILD_INTERFACE:${JSON_INCLUDE_DIR}>
+            $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
+        )
+        set(JSON_TARGET devdat_json_wrapper)
+        set(EXPORT_JSON_TARGET TRUE)
     else()
-        # Find system package
-        message(STATUS "Finding system nlohmann_json package")
+        # When using standard system package, handle dependency in config file
         find_package(nlohmann_json REQUIRED)
         set(JSON_TARGET nlohmann_json::nlohmann_json)
+        # We'll handle this dependency in the config file
+        set(EXPORT_JSON_TARGET FALSE)
     endif()
 else()
-    # Fetch our own copy
+    # Download nlohmann_json at configure time
     message(STATUS "Fetching nlohmann_json")
     include(FetchContent)
     FetchContent_Declare(
@@ -47,10 +57,22 @@ else()
         GIT_TAG v3.11.2
     )
     FetchContent_MakeAvailable(nlohmann_json)
-    set(JSON_TARGET nlohmann_json::nlohmann_json)
 
-    # Note: When not using system JSON, we'll need to ensure the headers are installed
-    set(INSTALL_JSON_HEADERS TRUE)
+    # Create our own interface that will be included in the export set
+    add_library(devdat_json_wrapper INTERFACE)
+    target_include_directories(devdat_json_wrapper INTERFACE 
+        $<BUILD_INTERFACE:${nlohmann_json_SOURCE_DIR}/include>
+        $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
+    )
+    
+    # Install the headers
+    install(
+        DIRECTORY ${nlohmann_json_SOURCE_DIR}/include/
+        DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
+    )
+    
+    set(JSON_TARGET devdat_json_wrapper)
+    set(EXPORT_JSON_TARGET TRUE)
 endif()
 
 # Create the library (header-only)
@@ -78,35 +100,28 @@ add_library(${PROJECT_NAME}::devdat ALIAS devdat)
 include(GNUInstallDirs)
 set(INSTALL_CONFIGDIR ${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME})
 
-# Install the headers
+# Install headers
 install(
     DIRECTORY include/
     DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
 )
 
-# If we fetched JSON and need to install the headers
-if(DEFINED INSTALL_JSON_HEADERS)
+# Install targets - always install devdat
+if(EXPORT_JSON_TARGET)
+    # If we created our own JSON wrapper, install both together
     install(
-        DIRECTORY ${nlohmann_json_SOURCE_DIR}/include/
-        DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
+        TARGETS devdat devdat_json_wrapper
+        EXPORT ${PROJECT_NAME}Targets
     )
-endif()
-
-# Install the target
-install(
-    TARGETS devdat
-    EXPORT ${PROJECT_NAME}Targets
-)
-
-# If using a custom JSON interface target, install it too
-if(DEVDAT_USE_SYSTEM_JSON AND DEFINED JSON_INCLUDE_DIR)
+else()
+    # Otherwise just install devdat
     install(
-        TARGETS json_interface
+        TARGETS devdat
         EXPORT ${PROJECT_NAME}Targets
     )
 endif()
 
-# Export the targets
+# Export targets
 install(
     EXPORT ${PROJECT_NAME}Targets
     FILE ${PROJECT_NAME}Targets.cmake
@@ -116,6 +131,8 @@ install(
 
 # Create config files
 include(CMakePackageConfigHelpers)
+
+# Create config file variables
 configure_file(
     ${CMAKE_CURRENT_SOURCE_DIR}/cmake/devdatConfig.cmake.in
     ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}Config.cmake
@@ -128,15 +145,15 @@ write_basic_package_version_file(
     COMPATIBILITY SameMajorVersion
 )
 
-# Install the config files
+# Install config files
 install(
     FILES
         ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}Config.cmake
         ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake
     DESTINATION ${INSTALL_CONFIGDIR}
 )
 
-# Add the tests if enabled
+# Add tests if enabled
 if(BUILD_TESTING)
     enable_testing()
     add_subdirectory(tests)

cmake/devdatConfig.cmake.in

@@ -2,25 +2,15 @@
 
 include(CMakeFindDependencyMacro)
 
-# Find or load CUDA toolkit (required for Thrust)
+# Find CUDA toolkit (required for Thrust)
 find_dependency(CUDAToolkit REQUIRED)
 
-# Handle nlohmann_json dependency
-if(@DEVDAT_USE_SYSTEM_JSON@)
-    # Check if we used a custom include path provided by superbuild
-    if(NOT TARGET json_interface)
-        # We used the system package during build
-        find_dependency(nlohmann_json REQUIRED)
-    endif()
-    # Otherwise, json_interface target is already defined in the Targets file
+# Handle nlohmann_json dependency - only if we didn't export our own wrapper
+if(@DEVDAT_USE_SYSTEM_JSON@ AND NOT @EXPORT_JSON_TARGET@)
+    find_dependency(nlohmann_json REQUIRED)
 endif()
 
 # Include the exported targets
 include("${CMAKE_CURRENT_LIST_DIR}/@PROJECT_NAME@Targets.cmake")
 
-# Provide compatibility with older FindPackage behavior
-set(devdat_FOUND TRUE)
-set(devdat_VERSION @PROJECT_VERSION@)
-set(devdat_INCLUDE_DIRS "${CMAKE_CURRENT_LIST_DIR}/../../../include")
-
 message(STATUS "Found @PROJECT_NAME@ @PROJECT_VERSION@")