rewrite_js_imports.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

from __future__ import print_function

import io
import os
import re
import sys
from os import path

basedir = os.getcwd()
import_line = re.compile(r'''^import.+'(?P<importpath>(?P<backtrack>(?:\.\./?){1,})(?P<fileref>.+))';?$''')

try:
    target_file = sys.argv[1]
except IndexError:
    print('usage: {} [target_file]'.format(sys.argv[0]))
    sys.exit(1)

target_file = path.abspath(target_file)
if not path.exists(target_file):
    print('{}: path does not exist'.format(target_file))
    sys.exit(1)


def path_diff(base, target):
    ''' Difference between base and target.
        Returns the part of target that is not common.
    '''

    common = path.commonprefix([base, target])
    return target[len(common)+1:]


parent_path = path.dirname(target_file)

print('- base dir:', basedir, file=sys.stderr)
print('  parent dir:', parent_path, file=sys.stderr)
print('  rewriting target:', target_file, file=sys.stderr)
print('  imports:', file=sys.stderr)

contents = []

with io.open(target_file, 'r') as f:
    for line in f.readlines():
        imp = import_line.match(line)
        if not imp:
            contents.append(line.rstrip())
            continue

        relative_path = imp.group('importpath')
        _, extension = path.splitext(relative_path)
        if len(extension) == 0:
            # Assume no extension == `.js`
            relative_path_ext = '{}.js'.format(relative_path)
        else:
            relative_path_ext = relative_path

        absolute_path = path.join(parent_path, relative_path_ext)
        resolved_path = path.abspath(absolute_path)
        new_import_path, _ = path.splitext(path_diff(basedir, resolved_path))
        old_string = imp.string.strip()
        new_string = old_string.replace(relative_path, new_import_path)

        print('   - string: {}'.format(old_string), file=sys.stderr)
        print('     groups:', file=sys.stderr)
        print('       backtrack: {}'.format(imp.group('backtrack')), file=sys.stderr)
        print('       fileref: {}'.format(imp.group('fileref')), file=sys.stderr)
        print('       importpath: {}'.format(imp.group('importpath')), file=sys.stderr)
        print('     absolute_import_path: {}'.format(absolute_path), file=sys.stderr)
        print('     resolved_import_path: {}'.format(resolved_path), file=sys.stderr)
        if not path.exists(resolved_path):
            print('     error: resolve_import_path does not exist', file=sys.stderr)
            continue
        print('     new_import_path: {}'.format(new_import_path), file=sys.stderr)
        print('     new_import_string: {}'.format(new_string), file=sys.stderr)

        contents.append(new_string)

if os.getenv('DRY_RUN', 'false').lower() in ['1', 't', 'true', 'y', 'yes']:
    sys.exit(0)

with io.open(target_file, 'r') as src:
    with io.open(target_file + '.bak', 'w') as dest:
        dest.write(src.read())

with io.open(target_file, 'w') as dest:
    dest.write('\n'.join(contents))