Changed the way the hash is created in hash_inputs()

[Generhr]

I changed the way the hash is created in hash_inputs() because building a project with VSCode and Ninja outputs many thousands of lines of code when running this part of the original code:

    proc = subprocess.Popen(
        co_args,
        stdout=subprocess.PIPE,
        stderr=subprocess.PIPE
    )
    stdout, stderr = proc.communicate()
    if stderr:
        return None

which causes the project to hang indefinately.

I also noticed that stdout and stderr get switched around when compiling with cl.exe vs clang.exe although I can no longer be sure that was the case.

The method now calculates the hash with the time the source file was last modified, the lines within any .clang-tidy config files, and then the args. The last two are more or less the same as the original code although the method I use to find the .clang-tidy is different and requires a new arg to be passed to clang-tidy: --directories_with_clang_tidy=<file1*file2*...>. This can be achieved in CMake with the following code:

cmake_minimum_required(VERSION 3.10)
project(ctcache-example VERSION 1.0)

find_program(CLANG_TIDY_COMMAND clang-tidy)

add_executable(bad01 bad01.cpp)
target_compile_options(bad01 PRIVATE -pedantic;-Wall;-Werror)

if(CLANG_TIDY_COMMAND)
    function(find_all_directories_with_clang_tidy VARIABLE)
        file(GLOB CLANG_TIDY_FILES "${CMAKE_CURRENT_SOURCE_DIR}/.clang-tidy")

        if(CLANG_TIDY_FILES)
            list(APPEND DIRECTORIES_WITH_CLANG_TIDY ${CMAKE_CURRENT_SOURCE_DIR})
        endif()

        file(GLOB ALL_PROJECT_FILES
             LIST_DIRECTORIES true
             "${CMAKE_CURRENT_SOURCE_DIR}/*"
        )

        foreach(DIRECTORY ${ALL_PROJECT_FILES})
            if(IS_DIRECTORY ${DIRECTORY})
                get_filename_component(DIR_NAME ${DIRECTORY} NAME)

                if(NOT DIR_NAME STREQUAL "build")
                    # Check if the directory contains a .clang-tidy file
                    file(GLOB CLANG_TIDY_FILES "${DIRECTORY}/.clang-tidy")

                    # If so, add the directory to `DIRECTORIES_WITH_CLANG_TIDY`
                    if(CLANG_TIDY_FILES)
                        list(APPEND DIRECTORIES_WITH_CLANG_TIDY ${DIRECTORY})
                    endif()
                endif()
            endif()
        endforeach()

        # CMake splits args up with ";" so use "*" to keep all the directories together, folders can't contain "*" in their name so this should be safe
        string(REPLACE ";" "*" DIRECTORIES_WITH_CLANG_TIDY "${DIRECTORIES_WITH_CLANG_TIDY}")

        set(${VARIABLE}
            ${DIRECTORIES_WITH_CLANG_TIDY}
            PARENT_SCOPE
        )
    endfunction()

    find_all_directories_with_clang_tidy(DIRECTORIES_WITH_CLANG_TIDY)

    if(DIRECTORIES_WITH_CLANG_TIDY)
        set_target_properties(bad01 PROPERTIES CXX_CLANG_TIDY ${CLANG_TIDY_COMMAND} --directories_with_clang_tidy=${DIRECTORIES_WITH_CLANG_TIDY})
    else()
        set_target_properties(bad01 PROPERTIES CXX_CLANG_TIDY ${CLANG_TIDY_COMMAND})
    endif()
endif()

I used "*" because (at least on Windows) this character can not be used in a folder name. I have only done limited testing with my hobby projects, there may be other source_file_extensions to consider when identifying the source file clang-tidy is being called on.

Thank you for creating such a cool tool. I spent about a day trying to figure out what the issue was and how to fix it but I'm sure this will save me a great deal of time in the future.

[matus-chochlik]

thanks for the PR