Implement "VisitFlow" - #1263
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Currently the AST traversal visitor pattern walks the entire tree, even when it doesn't strictly need to. This is bad for performance, which is especially wasteful as we precompute alot of metadata while building the AST. This also means some code (e.g. reduce_colors) needs to manage its own control flow to avoid "over reducing" some nodes. Really we should be able to skip descending into subtrees. This change refactors the Visit code to return a ControlFlow type, with subtype enums that control how visitors should descend into the tree. Each visit method can either break (stop the whole visit flow), skip children (so only the exit_ fires) or descend (the default). This also refactors the various consumers to take advantage of this new feature, including the selector engine in csskit_ast.
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## [0.0.27] - 2026-07-04 ### Other Changes - Fuzz: minimize corpus, and do so on nightly fuzz build (#1257) ([#1257](#1257)) - CI: Ensure benches build (#1259) ([#1259](#1259)) ### Css_ast - css_ast/css_parse: Improve peeking robustness. (#1238) ([#1238](#1238)) - Regenerate css_ast/src/values from csswg drafts (#1242) ([#1242](#1242)) - Regenerate css_ast/src/values from csswg drafts (#1254) ([#1254](#1254)) - fuzz: new parser findings 2026-06-19 (#1232) ([#1232](#1232)) - css_ast: Refactor assert_specificity to use closure pattern (#1261) ([#1261](#1261)) - css_ast: derive(ToSpan) on WebkitFunctionalPseudoClass (#1262) ([#1262](#1262)) - Implement "VisitFlow" (#1263) ([#1263](#1263)) ### Css_parse - fuzz: new parser findings 2026-07-01 (#1260) ([#1260](#1260)) ### Csskit - chore(deps): update dependencies (patch) (#1243) ([#1243](#1243)) ### Csskit_derives - chore(deps): update rust crate itertools to 0.15.0 (#1246) ([#1246](#1246)) ### Csskit_vscode - chore(deps): update dependencies to v1.68.0 (#1247) ([#1247](#1247)) - fix(deps): update dependencies (patch) (#1255) ([#1255](#1255)) [forcebuild]
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## [0.0.27] - 2026-07-04 ### Other Changes - Fuzz: minimize corpus, and do so on nightly fuzz build (#1257) ([#1257](#1257)) - CI: Ensure benches build (#1259) ([#1259](#1259)) ### Css_ast - css_ast/css_parse: Improve peeking robustness. (#1238) ([#1238](#1238)) - Regenerate css_ast/src/values from csswg drafts (#1242) ([#1242](#1242)) - Regenerate css_ast/src/values from csswg drafts (#1254) ([#1254](#1254)) - fuzz: new parser findings 2026-06-19 (#1232) ([#1232](#1232)) - css_ast: Refactor assert_specificity to use closure pattern (#1261) ([#1261](#1261)) - css_ast: derive(ToSpan) on WebkitFunctionalPseudoClass (#1262) ([#1262](#1262)) - Implement "VisitFlow" (#1263) ([#1263](#1263)) ### Css_parse - fuzz: new parser findings 2026-07-01 (#1260) ([#1260](#1260)) ### Csskit - chore(deps): update dependencies (patch) (#1243) ([#1243](#1243)) ### Csskit_derives - chore(deps): update rust crate itertools to 0.15.0 (#1246) ([#1246](#1246)) ### Csskit_vscode - chore(deps): update dependencies to v1.68.0 (#1247) ([#1247](#1247)) - fix(deps): update dependencies (patch) (#1255) ([#1255](#1255))
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## [0.0.27] - 2026-07-04 ### Other Changes - Fuzz: minimize corpus, and do so on nightly fuzz build (#1257) ([#1257](#1257)) - CI: Ensure benches build (#1259) ([#1259](#1259)) ### Css_ast - css_ast/css_parse: Improve peeking robustness. (#1238) ([#1238](#1238)) - Regenerate css_ast/src/values from csswg drafts (#1242) ([#1242](#1242)) - Regenerate css_ast/src/values from csswg drafts (#1254) ([#1254](#1254)) - fuzz: new parser findings 2026-06-19 (#1232) ([#1232](#1232)) - css_ast: Refactor assert_specificity to use closure pattern (#1261) ([#1261](#1261)) - css_ast: derive(ToSpan) on WebkitFunctionalPseudoClass (#1262) ([#1262](#1262)) - Implement "VisitFlow" (#1263) ([#1263](#1263)) ### Css_parse - fuzz: new parser findings 2026-07-01 (#1260) ([#1260](#1260)) ### Csskit - chore(deps): update dependencies (patch) (#1243) ([#1243](#1243)) ### Csskit_derives - chore(deps): update rust crate itertools to 0.15.0 (#1246) ([#1246](#1246)) ### Csskit_vscode - chore(deps): update dependencies to v1.68.0 (#1247) ([#1247](#1247)) - fix(deps): update dependencies (patch) (#1255) ([#1255](#1255))
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Currently the AST traversal visitor pattern walks the entire tree, even when it
doesn't strictly need to. This is bad for performance, which is especially
wasteful as we precompute alot of metadata while building the AST. This also
means some code (e.g. reduce_colors) needs to manage its own control flow to
avoid "over reducing" some nodes. Really we should be able to skip descending
into subtrees.
This change refactors the Visit code to return a ControlFlow type, with subtype
enums that control how visitors should descend into the tree. Each visit method
can either break (stop the whole visit flow), skip children (so only the exit_
fires) or descend (the default). This also refactors the various consumers to
take advantage of this new feature, including the selector engine in csskit_ast.