fix(compiler): remove deprecated shadow CSS encapsulation polyfills#68666
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mattrbeck wants to merge 1 commit into
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fix(compiler): remove deprecated shadow CSS encapsulation polyfills#68666mattrbeck wants to merge 1 commit into
mattrbeck wants to merge 1 commit into
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Completely remove support for `polyfill-next-selector`, `polyfill-unscoped-rule`, and `polyfill-rule` from `shadow_css.ts`, along with their associated methods and regular expressions. Also delete `polyfills_spec.ts` entirely.
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JoostK
approved these changes
May 11, 2026
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Completely remove support for
polyfill-next-selector,polyfill-unscoped-rule, andpolyfill-rulefromshadow_css.ts, along with their associated methods and regular expressions. Also deletepolyfills_spec.tsentirely.Support for these polyfills has existed since 2015, introduced in d67f029 before the Shadow DOM spec was even finalized. They were not specifically called out as features, but simply part of a port from the web component prototype polyfill.
The spec has been published for over 10 years now. These polyfills are no longer required.
Note:
polyfill-rule { content: ':host-context(.foo)' }now becomespolyfill-rule[contenta] { content: '.foo-shadowcsshost-no-combinator' ... }due to the nature of our regex-based parsing. This is true for other strings containing:host-context()today anyway, though. Just one more reason it'd be nice to have a real parser. Fixing that is out of scope in this PR.