make_single_header.py

#!/usr/bin/env python3

import re
import sys
import os
from os.path import dirname, join as path_join, abspath, exists

from pathlib import Path

extra_paths = [path_join(dirname(abspath(__file__)), "include")]


def find_file(included_name, current_file):
    current_dir = dirname(abspath(current_file))
    for idir in [current_dir] + extra_paths:
        try_path = path_join(idir, included_name)
        if exists(try_path):
            return try_path
    return None


def process_file(
    file_path,
    out_lines=[],
    front_matter_lines=[],
    back_matter_lines=[],
    processed_files=[],
):
    out_lines += "//BEGIN_FILE_INCLUDE: " + file_path + "\n"
    with open(file_path, "r") as f:
        for line in f:
            m_inc = re.match(r'# *include\s*[<"](.+)[>"]\s*', line)
            if m_inc:
                inc_name = m_inc.group(1)
                inc_path = find_file(inc_name, file_path)
                if inc_path is not None:
                  inc_path_res = str(Path(inc_path).resolve())
                  if inc_path_res not in processed_files:
                        processed_files += [inc_path_res]
                        process_file(
                            inc_path_res,
                            out_lines,
                            front_matter_lines,
                            back_matter_lines,
                            processed_files,
                        )
                else:
                  # assume it's a system header
                  out_lines += [line]
                continue
            m_once = re.match(r"#pragma once\s*", line)
            # ignore pragma once; we're handling it here
            if m_once:
                continue
            # otherwise, just add the line to the output
            if line[-1] != "\n":
                line = line + "\n"
            out_lines += [line]
    out_lines += "//END_FILE_INCLUDE: " + file_path + "\n"
    return (
        "".join(front_matter_lines)
        + "\n"
        + "".join(out_lines)
        + "".join(back_matter_lines)
    )


if __name__ == "__main__":
    print(
        process_file(
            str(Path(sys.argv[1]).resolve()),
            [],
            # We use an include guard instead of `#pragma once` because Godbolt will
            # cause complaints about `#pragma once` when they are used in URL includes.
            [
                "#ifndef _MDSPAN_SINGLE_HEADER_INCLUDE_GUARD_\n",
                "#define _MDSPAN_SINGLE_HEADER_INCLUDE_GUARD_\n",
            ],
            ["#endif // _MDSPAN_SINGLE_HEADER_INCLUDE_GUARD_\n"],
            [str(Path(sys.argv[1]).resolve())],
        )
    )