Parses JSON allowing for trailing commas and comments using //

parse_json_cfg.py

import re
import json

ONELINE_COMMENT_RE = re.compile(r"""
    ^                       # comment must be at the start of the line
    \s*                     # arbitrary whitespace
    //                      # start of the comment
    (.*)                    # the comment
    $                       # until the end of line
""", re.MULTILINE | re.VERBOSE)

INLINE_COMMENT_RE = re.compile(r"""
    ([\,\"\[\]\{\}\d])      # anythig that might end a expression
    \s+                     # comment must be preceded by whitespace
    //                      # start of the comment
    \s                      # and succeded by whitespace
    (?:[^\"\]\}\{\[]*)      # the comment (except things which might be json)
    $                       # until the end of line
""", re.MULTILINE | re.VERBOSE)

TRAILING_COMMA_RE = re.compile(r"""
    ,                       # the comma
    (?:\s*)                 # arbitrary whitespace
    $                       # only works if the trailing comma is followed by newline
    (\s*)                   # arbitrary whitespace
    ([\]\}])                # end of an array or object
""", re.MULTILINE | re.VERBOSE)


def parse_json_cfg(raw_data):
    """Parses JSON allowing for trailing commas and comments using //
    
    Note: Comments must be preceded by whitespace or newline.
    """
    if isinstance(raw_data, bytes):
        raw_data = raw_data.decode('utf-8')
    raw_data = ONELINE_COMMENT_RE.sub(r"", raw_data)
    raw_data = INLINE_COMMENT_RE.sub(r"\1", raw_data)
    raw_data = TRAILING_COMMA_RE.sub(r"\1\2", raw_data)
    return json.loads(raw_data)