Noisy error on malformed CSS

[Synchro]

Much like #179, I've been getting this from something malformed:

2015-09-30 14:43:49 DOMXPath::query(): Invalid predicate
#0 System_ErrorHandler->ERROR_HANDLER
#1 DOMXPath->query line 287
#2 Pelago\Emogrifier->process line 211
#3 Pelago\Emogrifier->emogrify line 44

That line is:

$nodesMatchingCssSelectors = $xpath->query($this->translateCssToXpath($selector['selector']));

So it may well be fixed by a fix for #179 by eliminating the bogus selector, but it shouldn't throw a noisy error like this anyway. Better to just ignore the content. When I've tracked down the content responsible for this error, I'll add it in here so we can build a test for it.

[oliverklee]

What CSS is causing this problem?

[Renkas]

I got the same problem.

Maybe this helps to track down the problem?

PHP Warning – yii\base\ErrorException

DOMXPath::query(): Invalid predicate
in /var/www/vendor/pelago/emogrifier/Classes/Emogrifier.php – DOMXPath::query('//a[href^="tel"]') at line 745

[oliverklee]

Okay, so it looks like Emogrifier currently does not support negative attribute selectors (i.e., this is missing feature). Anyone willing to implement this?

[Synchro]

That just sounds like XPath and CSS selectors do not share the same syntax for that kind of lookup. I suspect in my case it was simply malformed CSS rather than a missing feature - e.g. if someone puts HTML tags in the CSS, which I've seen. From the source of my CSS, I strongly suspect it's just random junk rather than anything as sophisticated as this missing selector, so the rename may not be quite appropriate.

[oliverklee]

Okay, I've reverted the changes to this ticket. Thanks for the input! (We already have #227 for the missing feature anyway.)

[oliverklee]

@Renkas: So it looks like you're experiencing #227.

[Synchro]

I've managed to track down some CSS that's causing this error - it's an empty media query.

In the Emogrifier class, the extractMediaQueriesFromCss method finds the media queries, but having an empty one makes it go out of sync. Note that it will only go wrong if you have another media query after the empty one.

I've set up the content and the regex it uses here, and you can see it going wrong.

Following on from that, when it gets to existsMatchForCssSelector, the first CSS selector it passes is:

}

table.body

Which is invalid, but still gets translated into the invalid XPath:

//}//table[contains(concat(" ",@class," "),concat(" ","body"," "))]

After which I get the error:

2016-04-27 14:43:19 DOMXPath::query(): Invalid expression
#0 My_ErrorHandler->ERROR_HANDLER
#1 DOMXPath->query line 956
#2 Pelago\Emogrifier->existsMatchForCssSelector line 913
#3 Pelago\Emogrifier->copyCssWithMediaToStyleNode line 391
#4 Pelago\Emogrifier->process line 276
#5 Pelago\Emogrifier->emogrify line 44

So it would be good if Emogrifier could cope with a missing media query body.

Meanwhile, I'll try to track down why my media queries are empty - I supect an old version of CSSTidy may be at fault.