1827941 - Make @import preload scanner deal well with supports()

Status: RESOLVED FIXED

(Core :: CSS Parsing and Computation, task, P3)

Description

[Emilio Cobos Álvarez (:emilio)]

We should consider fixing layout/style/ImportScanner.cpp so that we don't preload @import ... supports() if we don't actually support the relevant feature.

Comment 1

[Oliver Medhurst [:canadahonk]]

Attachment: Bug 1827941 - Do not preload nonmatching @import supports()

Added evaluating supports() conditions in the import preload scanner
and not emitting URLs if they do not match.

There is no use preloading imports for features we do not support,
as they will never be loaded since supports() conditions cannot
change mid-page.

WIP. Todo:

• Address TODO comments added
• Testing/etc

Comment 2

[Oliver Medhurst [:canadahonk]]

@emilio would you mind looking at the patch when free and seeing if you can tell why 1 new gtest is failing? Can't find a cause myself, thanks!

Comment 3

[Emilio Cobos Álvarez (:emilio)]

So you're doing:

if (OptionalSupportsMatches(...)) {
  EmitUrl();
}

But EmitUrl() not only emits the url but also resets the rule state, and you're not doing that if the supports doesn't match.

So it seems you should move the supports() check to EmitUrl(), also so that it gets caught in early-eof.

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/0a9fbe8c409f
Do not preload nonmatching @import supports() r=emilio

Comment 5

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Created web-platform-tests PR https://github.com/web-platform-tests/wpt/pull/39678 for changes under testing/web-platform/tests

Comment 6

[Norisz Fay [:noriszfay]]

https://hg.mozilla.org/mozilla-central/rev/0a9fbe8c409f

Comment 7

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Upstream PR merged by moz-wptsync-bot