cmake_configure_file.py

#!/usr/bin/env python

"""A re-implementation of CMake's configure_file substitution semantics.  This
implementation is incomplete, and may not produce the same result as CMake in
all (or even many) cases.

The CMake documentation of the configure_file macro is:
https://cmake.org/cmake/help/latest/command/configure_file.html

"""

import argparse
import os
import re
import sys

from collections import OrderedDict

# Looks like "#cmakedefine VAR ..." or "#cmakedefine01 VAR".
_cmakedefine = re.compile(r'^#cmakedefine(01)? ([^ \r\n]+)(.*?)([\r\n]+)')

# Looks like "@VAR@" or "${VAR}".
_varsubst = re.compile(r'^(.*?)(@.+?@|\$\{.+?\})(.*)([\r\n]*)')


# Transform a source code line per CMake's configure_file semantics.
def _transform(line, definitions):
    # Replace define statements.
    match = _cmakedefine.match(line)
    if match:
        maybe01, var, rest, newline = match.groups()
        defined = var in definitions
        if maybe01:
            return '#define ' + var + [' 0', ' 1'][defined] + newline
        elif defined:
            line = '#define ' + var + rest + newline
        else:
            return '/* #undef ' + var + ' */' + newline

    # Replace variable substitutions.
    while True:
        match = _varsubst.match(line)
        if not match:
            break
        before, xvarx, after, newline = match.groups()
        if xvarx[0] == '$':
            assert len(xvarx) >= 4
            assert xvarx[1] == '{'
            assert xvarx[-1] == '}'
            var = xvarx[2:-1]
        elif xvarx[0] == '@':
            assert len(xvarx) >= 3
            assert xvarx[-1] == '@'
            var = xvarx[1:-1]
        assert len(var) > 0

        value = definitions.get(var)
        if value is None:
            raise KeyError('Missing definition for ' + var)
        line = before + value + after + newline

    return line

# Looks like "set(VAR value)".
_set_var = re.compile(r'^\s*set\s*\(\s*(.+)\s+(.+)\s*\)\s*$')


# From a line of CMakeLists.txt, return a set(...) key-value pair, if found.
def _extract_definition(line, prior_definitions):
    match = _set_var.match(line)
    if not match:
        return dict()
    var, value = match.groups()
    try:
        value = _transform(value, prior_definitions)
    except KeyError:
        return dict()
    if value.startswith('"'):
        assert value.endswith('"')
        value = value[1:-1]
    return {var: value}


# Load our definitions dict, given the command-line args.
def _setup_definitions(args):
    result = OrderedDict()
    for item in args.defines:
        if '=' in item:
            key, value = item.split('=', 1)
            result[key] = value
        else:
            result[item] = 1

    for filename in args.cmakelists:
        with open(filename, 'r') as cmakelist:
            for line in cmakelist.readlines():
                definition = _extract_definition(line, result)
                result.update(definition)

    return result


def main():
    parser = argparse.ArgumentParser()
    parser.add_argument('--input', metavar='FILE')
    parser.add_argument('--output', metavar='FILE')
    parser.add_argument(
        '-D', metavar='NAME', dest='defines', action='append', default=[])
    parser.add_argument(
        '--cmakelists', action='append', default=[])
    args = parser.parse_args()
    if args.input is None or args.output is None:
        parser.print_usage()
        sys.exit(1)
    definitions = _setup_definitions(args)

    with open(args.input, 'r') as input_file:
        with open(args.output + '.tmp', 'w') as output_file:
            for input_line in input_file.readlines():
                output_line = _transform(input_line, definitions)
                output_file.write(output_line)
    os.rename(args.output + '.tmp', args.output)

if __name__ == '__main__':
    main()