Reparse file in silent mode after a CSS parsing error

[gmetais]

Hi!

I've seen that the CSS parser used by analyze-css has a 'silent' option: https://github.com/reworkcss/css#cssparsecode-options

Here's my idea: analyze-css could parse the CSS file a first time without this option, to detect any parsing error.
Then, if there is one, restart parsing in silent mode so the rest of the file can be analyzed despite the error.

[macbre]

@gmetais, good idea!

How would the analyze-css client know that an error happened and silent mode was applied? Error (i.e. exit code different than zero) will not be emitted. Add an "error" entry next to generator and metrics in JSON results?

[gmetais]

It could also directly insert parsingErrors: 1 into the metrics. With an offender specifying where the error occurred in the file (when available).

But your idea is probably:

• clearer, as long as the css parser only returns one parsing error for the file, even if there are more.
• safer, as some other error cases could be transmitted this way.

[macbre]

@gmetais, CSS parser used by analyze-css can not be used easily in silent mode. It does not fail gracefully when parsing error happens. silent flag simply means "don't throw an exception", continue and return AST with missing fields. Proper handling of missing fields IMHO would be an overkill here.

Hence closing. Waiting for other ideas on how to implement it :)

[gmetais]

Another idea then.

If the silent option doesn't fit our needs, we could make a pull request to the css parser module for another option.

The option could be named listErrors. So there are 3 modes:

• normal: throws an error and stops parsing
• silent: ignores error and continues parsing
• listErrors: saves the error in a list and continues parsing

It looks like there's a place for this option, have a look at this function:
https://github.com/reworkcss/css/blob/master/lib/parse/index.js#L59-L71

The errors would be a new field in the JSON output:

{
  "type": "stylesheet",
  "stylesheet": {
    "rules": [...],
    "parsingErrors": [
      {
        "message": "mystyles.css:300:12:missing '}'",
        "reason": "missing '}'",
        "filename": "mystyles.css",
        "line": 300,
        "column": 12,
        "source": "..."
      }
    ]
  }
}

[gmetais]

I made this pull-request on the css module: reworkcss/css#64
It would be great if it could make its way to analyze-css!