import io
import difflib


def generate_or_check(manifest, args, path, func):
    """Generate/check a file with a single generator

    Return True if successful; False if a comparison failed.
    """

    outfile = io.StringIO()
    func(manifest, args, outfile)
    generated = outfile.getvalue()
    existing = path.read_text()

    if generated != existing:
        if args.generate:
            path.write_text(generated)
        else:
            print(f'File {path} differs from expected!')
            diff = difflib.unified_diff(
                generated.splitlines(), existing.splitlines(),
                str(path), '<expected>',
                lineterm='',
            )
            for line in diff:
                print(line)
            return False
    return True