Fix #584 text-shadow with multiple values

[jwang1919]

Fixes bug #584

Gave commas between CSS parenthesis statements like rgba leeway in the PrettyCSS validation.

I found that doing so inadvertently created another bug where multiple commas would flag as valid. I added another check to deal with this as well as added the requisite validations in the test case.

[outoftime]

@jwang1919 so I think we might be at a point where we should just contribute a fix upstream to PrettyCSS. We’ve done so before and the process was pretty painless—the library is well-factored and it’s easy to add tests and such.

I would lean in that direction because PrettyCSS itself has a full tokenizer and lexer built in, so adding support for a given syntactic construct is much more robust and expressive than trying to work around a parser error using regular expressions. (I admit to being a little lost looking at the regexps you introduce here, and I consider myself reasonably competent with regexps).

WDYT?

[jwang1919]

@outoftime Yeah that sounds like a better option to me as well.
I'll revisit this branch once I submit the PR and it gets accepted in the PrettyCSS library.

The regexp was a difficult come up with, but not too hard to interpret.
It looks for any strings that has a comma followed by another comma with any number of blank spaces in between.

,    // look for comma
(    // start lookahead assertion
?=   // positive assertion, only match for these things
\s*  // zero to many blank spaces
,    // a comma
)    // close lookahead assertion

[outoftime]

@jwang1919 gotcha. yeah I’ve only worked with lookaheads a couple times, that’s what threw me off.

FWIW, we don’t necessarily need to wait for PrettyCSS to integrate your patch—we could temporarily target https://github.com/popcodeorg/PrettyCSS (which I think I did in the past while waiting for PRs to get merged)

[jwang1919]

Okay, made the changes and submitted PRs to both the original branch and the popcode fork. Once those are dealt with, I can change this branch's code.

[jwang1919]

@outoftime When possible, please review again. I have pushed the fix onto the PrettyCSS library (the maintainer merged it pretty quickly) and I've updated the PrettyCSS library.

[outoftime]

Sick!! Awesome work on the upstream PR!