Repository navigation
Conversation
`:first-child`, `:last-child`, `:only-child`, `:nth-child()`, `:nth-last-child()` and the `-of-type` forms now match from a view's position among its parent's children. They were treated as states a view reports, like `:active`, and no view ever reported them, so CSS frameworks' rules for the ends of lists, button groups and cards (and Tailwind's `first:`/`last:`/`odd:` variants) never applied. Matching reuses the parent's getChildIndex/getChildAt/getChildrenCount, as the sibling combinators do, and a layout re-matches the siblings a change can affect: selectors that look back are flagged like `+` and `~`, and the ones that look forward (`:last-child`, `:nth-last-child()`) get the same treatment for the views before an added or removed child. `:nth-child(an+b of S)` is not supported.
`:root` matches the application's root view and each modal's root view (the views core gives the `ns-root` and `ns-modal` classes), with the specificity of a pseudo-class. CSS frameworks declare their custom properties and base styles on `:root`; core used to treat it as a state no view reported, so none of them applied.
|
View your CI Pipeline Execution ↗ for commit 0d88e51
💡 Verify your cache is correct by running tasks in a sandbox. Read docs ↗ ☁️ Nx Cloud last updated this comment at |
commit: |
Contributor
|
The main reason these were never implemented is because of performance and walking the tree. I'd hold off on this until we improve our CSS engine |
This branch has not been deployed
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
PR Checklist
What is the current behavior?
:first-child,:last-child,:nth-child(),:rootand the other structural pseudo-classes are treated as states a view reports, like:active, and no view ever reports them, so they never match. CSS frameworks rely on them heavily: Bootstrap uses:first-child/:last-childabout 300 times (the ends of list groups, button and input groups, cards), Tailwind'sfirst:,last:,odd:andeven:variants compile to them, and both declare their custom properties on:root.What is the new behavior?
:first-child,:last-child,:only-child,:nth-child(an+b),:nth-last-child(an+b)and the-of-typeforms match from the view's position among its parent's children, using the parent'sgetChildIndex/getChildAt/getChildrenCountas the sibling combinators do.odd,even,3,2n+1,-n+3are supported;:nth-child(an+b of S)is not and drops the selector.+and~(so the existinginsertChild/removeChildinvalidation covers them). Selectors that look forward (:last-child,:nth-last-child(),:last-of-type) get matching flags (hasNextSiblingSelectors,hasFollowingSiblingSelectors), andaddChild/insertChild/removeChildre-match the views before the change. Scopes without such selectors do no extra work.:rootmatches the application's root view and each modal's root view (the views core gives thens-rootandns-modalclasses), with the specificity of a pseudo-class.Tests:
css-structural-pseudo.spec.ts(10: matching, formulas, combinations with:not()/:is(), dependency flags, and re-matching on append/insert/remove in a StackLayout) and:rootcases incss-selector.spec.ts.Verified with all of these core PRs merged together (#11527–#11537):
apps/automatedpasses on the iOS 26.4 simulator (1830 OK, 0 failed) and on an Android API 36 emulator (1692 OK; the one failure is the network-dependentIMAGE-CACHE.test_ImageCache_ValidUrltimeout, which also passes on reruns).