old_contents: import argparse
  import json
  import sys
  
  import gcl
  from gcl import query
  from gcl import util
  
  
  def main(argv=None, stdin=None):
    parser = argparse.ArgumentParser(description='Convert (parts of) a GCL model file to JSON.')
    parser.add_argument('file', metavar='FILE', type=str, nargs='?',
                        help='File to parse')
    parser.add_argument('selectors', metavar='SELECTOR', type=str, nargs='*',
                        help='Subnodes to convert. The first selector will be treated as the root of the printed output.')
  
    args = parser.parse_args(argv or sys.argv[1:])
  
    try:
      if args.file and args.file != '-':
        model = gcl.load(args.file)
      else:
        model = gcl.loads((stdin or sys.stdin).read(), filename='<stdin>')
  
      sels = query.GPath(args.selectors)
      if not sels.everything():
        model = sels.select(model).deep()
  
      plain = util.to_python(model)
      sys.stdout.write(json.dumps(plain))
    except (gcl.ParseError, RuntimeError) as e:
      sys.stderr.write(str(e) + '\n')
      sys.exit(1)
  
new_contents: import argparse
  import json
  import sys
  
  import gcl
  from gcl import query
  from gcl import util
  
  
  def select(dct, path):
    for part in path:
      if not hasattr(dct, 'keys'):
        raise RuntimeError('Value %r cannot be indexed with %r' % (dct, part))
      if part not in dct:
        raise RuntimeError('Value %r has no key %r' % (dct, part))
      dct = dct[part]
    return dct
  
  
  def main(argv=None, stdin=None):
    parser = argparse.ArgumentParser(description='Convert (parts of) a GCL model file to JSON.')
    parser.add_argument('file', metavar='FILE', type=str, nargs='?',
                        help='File to parse')
    parser.add_argument('selectors', metavar='SELECTOR', type=str, nargs='*',
                        help='Select nodes to include in the JSON.')
    parser.add_argument('--root', '-r', metavar='PATH', type=str, default='',
                        help='Use the indicated root path as the root of the output JSON object (like a.b.c but without wildcards)')
  
    args = parser.parse_args(argv or sys.argv[1:])
  
    try:
      if args.file and args.file != '-':
        model = gcl.load(args.file)
      else:
        model = gcl.loads((stdin or sys.stdin).read(), filename='<stdin>')
  
      sels = query.GPath(args.selectors)
      if not sels.everything():
        model = sels.select(model).deep()
  
      plain = util.to_python(model)
  
      selectors = args.root.split('.') if args.root else []
      selected = select(plain, selectors)
  
      sys.stdout.write(json.dumps(selected))
    except (gcl.ParseError, RuntimeError) as e:
      sys.stderr.write(str(e) + '\n')
      sys.exit(1)
  
subject: Add proper root selector to gcl2json