fix(css): Merge duplicate nested at-rules#1917
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What is this change?
Merges duplicate children recursively when equivalent at-rules are nested, so repeated declarations under the same conditional scopes are emitted once.
Credit to @michaelabrahamian for providing the nested at-rule reproduction and expected output.
Fixes #1847
Why are we making this change?
mergeDuplicateAtRulesmerged matching top-level containers but treated each nested at-rule as an opaque serialized child. When nested blocks differed by even one declaration, both survived deduplication and produced redundant CSS.How are we making this change?
The plugin now merges equivalent sibling at-rules at each nesting level, deduplicates their children, and then recurses into the merged container. Matching remains scoped to the current parent, non-atomic
cssMapScopedrules remain untouched, and existing top-level ordering is preserved.A patch changeset for
@compiled/cssis included.Validation:
yarn test packages/css/src/plugins/__tests__/merge-duplicate-at-rules.test.ts --runInBand(6 tests)yarn test packages/css --runInBand(297 tests, 219 snapshots)yarn test --runInBand(5,132 tests, 436 snapshots)yarn lintyarn prettier:checkyarn buildNot run: visual regression tests, because this change operates on deterministic PostCSS output and has no rendered component changes.
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