CSS, "tuple index out of range"

[jaggzh]

  File ".../__init__.py", line 239, in __init__
    preprocess_stylesheet(
  File ".../css/__init__.py", line 1017, in preprocess_stylesheet
    rule_descriptors = dict(
  File ".../css/validation/descriptors.py", line 49, in preprocess_descriptors
    value = function(tokens, base_url)
  File ".../css/utils.py", line 153, in wrapper
    result = function(remove_whitespace(part), *args)
  File ".../css/validation/descriptors.py", line 145, in src
    tokens, token = tokens[:-1], tokens[-1]
IndexError: tuple index out of range

It's crashing on invalid .css entries with commas at the end, like:

@font-face {
  font-family: 'en-sym';
  src: url('res/DejaVuSans.ttf');
  src: url('res/DejaVuSans.ttf') format('truetype'),
}

It'd be difficult for most users to find what the problem is. I modified the code to print tokens to try to debug it:

Tokens: (<FunctionBlock url( … )>, <FunctionBlock format( … )>)
Tokens: (<FunctionBlock url( … )>, <FunctionBlock format( … )>)
Tokens: (<FunctionBlock url( … )>,)
Tokens: (<FunctionBlock url( … )>, <FunctionBlock format( … )>, <LiteralToken ,>)

So I found the issue was the comma, but maybe some useful output would be good here? The error is because tokens is empty, and the code's test for <= 2 items then assumes there's an actual last item anyway.

[liZe]

Thanks a lot for the bug report. It’s fixed and tested on master, feedback is welcome!