getting rid of json complexity

Author: kadeslu

CMakeLists.txt

@@ -24,57 +24,54 @@ endif()
 
 # Handle nlohmann_json dependency
 if(DEVDAT_USE_SYSTEM_JSON)
-    find_package(nlohmann_json REQUIRED)
-    set(JSON_TARGET nlohmann_json::nlohmann_json)
+    # Check if JSON_INCLUDE_DIR is provided by the superbuild
+    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)
+    else()
+        # Find system package
+        message(STATUS "Finding system nlohmann_json package")
+        find_package(nlohmann_json REQUIRED)
+        set(JSON_TARGET nlohmann_json::nlohmann_json)
+    endif()
 else()
-    # Download nlohmann_json at configure time
+    # Fetch our own copy
+    message(STATUS "Fetching nlohmann_json")
     include(FetchContent)
     FetchContent_Declare(
         nlohmann_json
         GIT_REPOSITORY https://github.com/nlohmann/json.git
         GIT_TAG v3.11.2
     )
     FetchContent_MakeAvailable(nlohmann_json)
+    set(JSON_TARGET nlohmann_json::nlohmann_json)
 
-    # Create our own interface that doesn't need to be exported
-    add_library(devdat_json_dep INTERFACE)
-    target_include_directories(devdat_json_dep 
-        INTERFACE 
-            $<BUILD_INTERFACE:${nlohmann_json_SOURCE_DIR}/include>
-            # Important: This is how consumers will find the headers
-            $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
-    )
-    
-    # Install the nlohmann_json headers directly to include directory
-    # This ensures they're found alongside our own headers
-    install(
-        DIRECTORY ${nlohmann_json_SOURCE_DIR}/include/
-        DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
-    )
-    
-    set(JSON_TARGET devdat_json_dep)
+    # Note: When not using system JSON, we'll need to ensure the headers are installed
+    set(INSTALL_JSON_HEADERS TRUE)
 endif()
 
 # Create the library (header-only)
 add_library(devdat INTERFACE)
 
-# Set target properties (note: header-only libraries use INTERFACE)
+# Set target properties
 target_include_directories(devdat
     INTERFACE
         $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
         $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
-        $<BUILD_INTERFACE:${CMAKE_CUDA_TOOLKIT_INCLUDE_DIRECTORIES}>
-        $<INSTALL_INTERFACE:${CMAKE_CUDA_TOOLKIT_INCLUDE_DIRECTORIES}>
+        ${CMAKE_CUDA_TOOLKIT_INCLUDE_DIRECTORIES}
 )
 
-# Link dependencies (using our local target and CUDA)
+# Link dependencies
 target_link_libraries(devdat
     INTERFACE
         ${JSON_TARGET}
         CUDA::toolkit
 )
 
-# Add an alias target for use within the build tree
+# Add an alias target
 add_library(${PROJECT_NAME}::devdat ALIAS devdat)
 
 # Installation
@@ -87,16 +84,24 @@ install(
     DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
 )
 
-# Install the target (note: header-only libraries have special install syntax)
+# If we fetched JSON and need to install the headers
+if(DEFINED INSTALL_JSON_HEADERS)
+    install(
+        DIRECTORY ${nlohmann_json_SOURCE_DIR}/include/
+        DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
+    )
+endif()
+
+# Install the target
 install(
     TARGETS devdat
     EXPORT ${PROJECT_NAME}Targets
 )
 
-if(NOT DEVDAT_USE_SYSTEM_JSON)
-    # Add our bundled dependency to the exported targets
+# If using a custom JSON interface target, install it too
+if(DEVDAT_USE_SYSTEM_JSON AND DEFINED JSON_INCLUDE_DIR)
     install(
-        TARGETS devdat_json_dep
+        TARGETS json_interface
         EXPORT ${PROJECT_NAME}Targets
     )
 endif()
@@ -111,8 +116,6 @@ install(
 
 # Create config files
 include(CMakePackageConfigHelpers)
-
-# Create a config file that handles dependencies
 configure_file(
     ${CMAKE_CURRENT_SOURCE_DIR}/cmake/devdatConfig.cmake.in
     ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}Config.cmake

cmake/devdatConfig.cmake.in

@@ -5,12 +5,22 @@ include(CMakeFindDependencyMacro)
 # Find or load CUDA toolkit (required for Thrust)
 find_dependency(CUDAToolkit REQUIRED)
 
-# Handle nlohmann_json dependency if using system version
+# Handle nlohmann_json dependency
 if(@DEVDAT_USE_SYSTEM_JSON@)
-    find_dependency(nlohmann_json REQUIRED)
+    # 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
 endif()
 
 # Include the exported targets
 include("${CMAKE_CURRENT_LIST_DIR}/@[email protected]")
 
+# 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@")