Allow disabling the processing of CSS

[cawa-93]

Basic info:

• Node.js version: v8.2.1
• jsdom version: ^11.2.0

Minimal reproduction case

If I try parse html contain

<style type="text/css">
@import url("/css/blok_add.css");
</style>

I get the following error:

Error: Could not parse CSS @import URL /css/blok_add.css relative to base URL "about:blank"
    at scanForImportRules (D:\Develop\parser\node_modules\jsdom\lib\jsdom\living\helpers\stylesheets.js:68:25)
    at exports.evaluateStylesheet (D:\Develop\parser\node_modules\jsdom\lib\jsdom\living\helpers\stylesheets.js:33:3)
    at HTMLStyleElementImpl._attach (D:\Develop\parser\node_modules\jsdom\lib\jsdom\living\nodes\HTMLStyleElement-impl.js:23:5)
    at HTMLTableDataCellElementImpl._attach (D:\Develop\parser\node_modules\jsdom\lib\jsdom\living\nodes\Node-impl.js:281:15)
    at HTMLTableDataCellElementImpl._attach (D:\Develop\parser\node_modules\jsdom\lib\jsdom\living\nodes\Element-impl.js:93:11)
    at HTMLTableRowElementImpl._attach (D:\Develop\parser\node_modules\jsdom\lib\jsdom\living\nodes\Node-impl.js:281:15)
    at HTMLTableRowElementImpl._attach (D:\Develop\parser\node_modules\jsdom\lib\jsdom\living\nodes\Element-impl.js:93:11)
    at HTMLTableSectionElementImpl._attach (D:\Develop\parser\node_modules\jsdom\lib\jsdom\living\nodes\Node-impl.js:281:15)
    at HTMLTableSectionElementImpl._attach (D:\Develop\parser\node_modules\jsdom\lib\jsdom\living\nodes\Element-impl.js:93:11)
    at HTMLTableElementImpl._attach (D:\Develop\parser\node_modules\jsdom\lib\jsdom\living\nodes\Node-impl.js:281:15)
    at HTMLTableElementImpl._attach (D:\Develop\parser\node_modules\jsdom\lib\jsdom\living\nodes\Element-impl.js:93:11)
    at HTMLDivElementImpl._attach (D:\Develop\parser\node_modules\jsdom\lib\jsdom\living\nodes\Node-impl.js:281:15)
    at HTMLDivElementImpl._attach (D:\Develop\parser\node_modules\jsdom\lib\jsdom\living\nodes\Element-impl.js:93:11)
    at HTMLTableDataCellElementImpl._attach (D:\Develop\parser\node_modules\jsdom\lib\jsdom\living\nodes\Node-impl.js:281:15)
    at HTMLTableDataCellElementImpl._attach (D:\Develop\parser\node_modules\jsdom\lib\jsdom\living\nodes\Element-impl.js:93:11)
    at HTMLTableRowElementImpl._attach (D:\Develop\parser\node_modules\jsdom\lib\jsdom\living\nodes\Node-impl.js:281:15)
    at HTMLTableRowElementImpl._attach (D:\Develop\parser\node_modules\jsdom\lib\jsdom\living\nodes\Element-impl.js:93:11)
    at HTMLTableSectionElementImpl._attach (D:\Develop\parser\node_modules\jsdom\lib\jsdom\living\nodes\Node-impl.js:281:15)
    at HTMLTableSectionElementImpl._attach (D:\Develop\parser\node_modules\jsdom\lib\jsdom\living\nodes\Element-impl.js:93:11)
    at HTMLTableElementImpl._attach (D:\Develop\parser\node_modules\jsdom\lib\jsdom\living\nodes\Node-impl.js:281:15)
    at HTMLTableElementImpl._attach (D:\Develop\parser\node_modules\jsdom\lib\jsdom\living\nodes\Element-impl.js:93:11)
    at HTMLDivElementImpl._attach (D:\Develop\parser\node_modules\jsdom\lib\jsdom\living\nodes\Node-impl.js:281:15)

The problem can be solved by specifying the parameter url.

new JSDOM(html, {url: 'http://example.com'})

However, I'm wondering if it's possible to completely disable the processing of CSS?

[domenic]

It's not possible at the moment. You can suppress errors using your own VirtualConsole though.

The correct thing to do is indeed to set a base URL.

[pawel-dubiel]

The ability to disable certain parts of jsdom features could help optimize performance. And when scrapping content the CSS processing is certainly not needed.

[cawa-93]

@pawel-dubiel, Right. In my case, I'm only interested in httml and manipulation with it. I do not need the processing of the CSS and javascript. I would like to disable all this, to improve the speed of work.

[pawel-dubiel]

@cawa-93 I'm just thinking if you don't need to use JS/CSS and you don't need DOM API you may consider using cheerio (which should be a few times faster, or at least it was a few years ago ).

[domenic]

Do you have any evidence of a performance increase? With my knowledge of jsdom's architecture, there shouldn't be much, if any, since it's all done lazily.

[pawel-dubiel]

@domenic
8x is a claim from https://github.com/cheeriojs/cheerio

"Blazingly fast: Cheerio works with a very simple, consistent DOM model. As a result parsing, manipulating, and rendering are incredibly efficient. Preliminary end-to-end benchmarks suggest that cheerio is about 8x faster than JSDOM."

And this old screencast https://vimeo.com/31950192 which at the end compares both jsdom and cheerio performance, but it's 6 years old.

It would be really interesting to see results from 2017.

But both projects have a different scope.

[domenic]

Yes, those Cheerio results are really dishonest, as we've mentioned to their author before. And they certainly have nothing to do with CSS.

[mikegleasonjr]

I'm in the camp where cssom fails to parse my CSS but I still need to parse the js.

[dontcallmedom]

I too would like to disable inline CSS parsing - it is mostly a waste of CPU and memory in my various usages of jsdom.

[domenic]

#2005 (comment)

[mikegleasonjr]

For me is having to write more code to gracefully handle CSS parsing "errors" that is bothering me. Even if my CSS is valid (It is just not supported by JSDOM's parser).

EDIT: maybe I should try again with the newer versions

[dontcallmedom]

Here is a script which, when run along with a downloaded copy of https://www.w3.org/TR/html52/single-page.html takes around 6 seconds less on my machine when evaluateStylesheet is commented out in HTMLStyleElement-impl.js:

const {JSDOM} = require("jsdom");
console.time("DOM parsing");
JSDOM.fromFile("single-page.html").then(dom => {
  console.timeEnd("DOM parsing");
});

[domenic]

That's great evidence; thanks!