Make sure that the headers are self-contained; fixes #528

[liuzicheng1987]

No description provided.

[gemini-code-assist]

Summary of Changes

Hello @liuzicheng1987, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances the robustness and maintainability of the reflectcpp library by introducing a mechanism to enforce header self-containment. A new CMake option allows developers to enable a build-time check that verifies each header file can be compiled in isolation. This is crucial for preventing subtle build errors, improving compilation times, and making the codebase easier to understand and refactor. The changes also include necessary adjustments to individual header files to ensure they meet this new standard, along with general code cleanup and formatting improvements.

Highlights

• New CMake Option for Header Self-Containment: A new CMake option, REFLECTCPP_CHECK_HEADERS, has been introduced. When enabled, this option triggers a build process to verify that all header files are self-contained, meaning they can be included independently without requiring other headers to be included beforehand.
• Automated Header Self-Containment Testing: The build system now includes a custom step that automatically generates a small C++ file for each public header. Each generated file simply includes its corresponding header, and these files are then compiled. This ensures that every header explicitly includes all its necessary dependencies, preventing hidden dependencies and improving modularity.
• Dependency Management Updates: The CMake configuration has been updated to integrate the REFLECTCPP_CHECK_HEADERS option into existing dependency logic. This ensures that when header checking is enabled, all required third-party libraries (e.g., via VCPKG) are correctly pulled in and linked for the header test builds.
• Header File Refinements: Numerous header files across various modules (e.g., rfl/avro, rfl/bson, rfl/capnproto, rfl/flexbuf, rfl/msgpack, rfl/parsing, rfl/internal, rfl/thirdparty/enchantum, rfl/yaml) have been modified to explicitly include previously implicit dependencies. This directly addresses the self-containment goal by making each header fully functional on its own.

Ignored Files

• Ignored by pattern: .github/workflows/** (2)
  • .github/workflows/linux.yaml
  • .github/workflows/macos.yaml

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[gemini-code-assist]

Code Review

This pull request aims to make headers self-contained by adding missing includes. The changes across the header files look correct. However, the CMake logic to verify self-contained headers is flawed. I've provided a suggestion to fix it. The main issue is that the test targets for each header are not configured with the necessary include paths and dependencies, which my suggestion addresses by linking them against the main reflectcpp library.

[gemini-code-assist]

The current implementation for checking if headers are self-contained is not correctly configured. The check_header_* targets are missing the necessary include directories and link dependencies from third-party libraries (like avro, bson, etc.). This will cause the compilation of the test sources to fail.

A better approach is to create executables for each header check and link them against the reflectcpp target. This ensures they inherit all the necessary public/interface dependencies and include paths. Using an executable also verifies that linking succeeds, which is a more thorough check than just compiling a static library.

I've also added a main function to the generated source file to make it a valid executable source.

if(REFLECTCPP_CHECK_HEADERS)
    file(GLOB_RECURSE PROJECT_HEADERS "include/*.hpp")

    set(TEST_DIR "${CMAKE_CURRENT_BINARY_DIR}/self_contained_tests")
    file(MAKE_DIRECTORY "${TEST_DIR}")

    foreach(HEADER_FILE ${PROJECT_HEADERS})
        string(MAKE_C_IDENTIFIER ${HEADER_FILE} HEADER_NAME)
        set(TEST_SOURCE_FILE "${TEST_DIR}/test_${HEADER_NAME}.cpp")

        file(GENERATE
            OUTPUT ${TEST_SOURCE_FILE}
            CONTENT "#include \"${HEADER_FILE}\"\nint main() { return 0; }\n"
        )

        add_executable(check_header_${HEADER_NAME} "${TEST_SOURCE_FILE}")
        target_link_libraries(check_header_${HEADER_NAME} PRIVATE reflectcpp)
        
        add_custom_target(check_${HEADER_NAME} ALL DEPENDS check_header_${HEADER_NAME})
    endforeach()
endif()