1850974 - :is(:host) doesn't work, but it probably should.

Status: RESOLVED FIXED

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

Description

[Emilio Cobos Álvarez (:emilio)]

Attachment: Test-case

Blink (at least, haven't checked WebKit) also has this bug, fwiw. See attached test-case.

This prevents nesting from working with :host rules, because the & is expanded to :is(<parent-selector>).

To fix this, we should probably change this code to not look at whether we're a featureless host selector, but at whether :host might match at all, and insert those into host_rules too, alongside with putting it in the normal rules.

It's a bit tricky, and then we somehow need to prevent stuff like :is(#foo, :host(#bar)) from matching a host with id foo...

Comment 1

[Emilio Cobos Álvarez (:emilio)]

WebKit also fails this test-case.

Comment 2

[Emilio Cobos Álvarez (:emilio)]

Attachment: Bug 1850974 - Make :is(:host) work. r=zrhoffman

Tests needed, but this should work per spec, see
https://github.com/w3c/csswg-drafts/issues/9509.

Tweak a bit the selector flags set up so that checking for :host
selectors during CascadeData rebuilds is cheap.

Tests needed for:

• Basic cases.
• Nesting.
• Ancestor selector.
• Ancestor selector with nesting.

So WIP for now.

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/3b13b5585380
Make :is(:host) work. r=zrhoffman

Comment 4

[Natalia Csoregi [:nataliaCs]]

Backed out for causing multiple failures e.g. parser crashes

• backout: https://hg.mozilla.org/integration/autoland/rev/f08bd867bf21d333c48d2a66c4e5c27021508277
• push: https://treeherder.mozilla.org/jobs?repo=autoland&group_state=expanded&revision=3b13b5585380e95b76444f10d65a42d3543bbd1a
• failure log:
  *gmake[4]: *** [/builds/worker/checkouts/gecko/config/makefiles/rust.mk:527: force-cargo-test-run] Error 101
  *PROCESS-CRASH | is_part() lied somehow? [@ selectors::parser::Selector<Impl>::parts] | /css/css-nesting/pseudo-part-crash.html

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/42822 for changes under testing/web-platform/tests

Comment 6

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

Upstream PR was closed without merging

Comment 7

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/8b16994e8df5
Make :is(:host) work. r=zrhoffman

Comment 8

[Noemi Erli[:noemi_erli]]

https://hg.mozilla.org/mozilla-central/rev/8b16994e8df5

Comment 9

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

Upstream PR merged by moz-wptsync-bot