Bug 191466 – CSS @imports in HTML missing quote marks are mistakenly hidden from the Preload Scanner

• Component: Page Loading
• Status: RESOLVED FIXED

[Harry Roberts]

**Example URL:**

https://csswizardry.com/demos/2018/11/import/blocked-by-css.html OR https://csswizardry.com/demos/2018/11/import/blocked-by-js.html

**Steps to reproduce the problem:**

1. Have a page with a synchronous `<link rel="stylesheet" />` and/or synchronous `<script src="">` BEFORE an in-page `@import url(style.css)` that omits the optional quote marks.
2. Reload page with Network panel open
3. Note lack of parallelisation: files are serialised
4. Edit `@import url(style.css)` to be `@import url("style.css")` (note addition of quote marks)
5. Refresh and observe waterfall
6. Parallelisation!

**What is the expected behaviour?**

I would expect the Preload Scanner to identify the IMPORT regardless of the presence of quote marks

**What went wrong?**

The Preload Scanner isn’t noticing @import URLs that omit OPTIONAL quotes

[Radar WebKit Bug Importer]

<rdar://problem/46031271>

[Yoav Weiss]

I'm currently fixing a similar (identical?) issue in Chromium's CSSPreloadScanner. Patch is up at https://chromium-review.googlesource.com/c/chromium/src/+/1331042/3

At the very least, the tests can be reused here.

[Ahmad Saleem]

Changes here - https://searchfox.org/wubkat/source/Source/WebCore/html/parser/CSSPreloadScanner.cpp#110

& 

Comments here - https://searchfox.org/wubkat/source/Source/WebCore/html/parser/CSSPreloadScanner.cpp#166 (No need to add {} here)

Comment here - https://chromium-review.googlesource.com/c/chromium/src/+/1331042/3/third_party/blink/renderer/core/html/parser/css_preload_scanner.cc#188

and then from here onward - change and just return String():

https://searchfox.org/wubkat/source/Source/WebCore/html/parser/CSSPreloadScanner.cpp#183-193

Add here remaining - https://searchfox.org/wubkat/source/Source/WebCore/html/parser/CSSPreloadScanner.cpp#201

[Ahmad Saleem]

https://wpt.fyi/results/loading?label=master&label=experimental&aligned&view=subtest&q=preloader-css-import

[Ahmad Saleem]

PR - https://github.com/WebKit/WebKit/pull/10346

[EWS]

Committed 261254@main (6851ca14bf62): <https://commits.webkit.org/261254@main>

Reviewed commits have been landed. Closing PR #10346 and removing active labels.