fix: tree-shake unused circular declarators exported via export list#10166
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Interesting. Rollup failures. I guess it's not about correctness but more of a behavior change. |
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Yeah, so I ignore the snapshot diff. Changing |
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…10166) ### Description Fixes #10165. `let f = () => {}, a = () => b(), b = () => a();` followed by `export { f, a, b }` kept the unused `a`/`b` pair in the output, while the equivalent inline form `export let F = ..., A = ..., B = ...` tree-shook them. Tree-shaking includes whole top-level statements. Before scanning, only exported multi-declarator declarations (and, under `keepNames`, all of them) were split into one statement per declarator, so demanding one binding of a bare declaration kept every declarator in it. The default dce-only minify pass normally cleans up such leftovers, but it counts references and cannot delete two functions that reference each other in a cycle — so the circular pair survived. The fix splits bare top-level multi-declarator declarations in the pre-scan the same way exported ones already are (`split_multi_declarator` in `tweak_ast_for_scanning.rs`), giving inclusion analysis per-declarator granularity. This matches esbuild, which creates one part per declarator. Two details: - The split (both the existing export path and the new bare path) is now limited to declarations where **every** declarator binds a plain identifier, because destructuring performs binding-time work (iterator calls, property reads). Previously the export path split when *any* declarator was a plain identifier. The regression fixture covers this with an iterator side effect that must survive when only a sibling plain binding is demanded. - The first replacement statement keeps the original statement span, so comments attached to the statement's start position stay attached. Snapshot changes are cosmetic: joined declarations now print as separate statements (all their declarators are used), and two fixtures with mixed identifier/destructuring declarations print grouped again. ### Alternatives explored - Gating the split on "a binding appears in an export list": covers the issue as filed but misses the same bug when the demand comes from inside the module (nothing exported at all), so the split is unconditional at the top level. - Relying on the minifier: reference-counting DCE fundamentally cannot remove closed reference cycles; only demand-driven inclusion can, and it needs per-declarator statements to do so. ### Test plan - New fixture `crates/rolldown/tests/rolldown/issues/10165` mirrors the issue (fails without the fix: `a`/`b` stay in the output) and asserts at runtime that a destructuring side effect next to an exported plain binding is preserved. - `cargo test --workspace`: green (1797 integration tests), 9 cosmetic snapshot updates. - `just test-node-rolldown`: green.
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## [1.1.5] - 2026-07-08 ### 🚀 Features - detect top-level import-binding reads as execution-order sensitive (#10180) by @hyf0 - sourcemap_filenames: add a sourcemapFileNames option (#9271) by @V1OL3TF0X - binding: record plugin hook result kind in tracing spans (#10154) by @IWANABETHATGUY - linking: skip side-effect-free modules in per-entry reachability (#10111) by @IWANABETHATGUY - improve error message for unresolved virtual imports (#10156) by @sapphi-red - add descriptive metadata to plugin API (#10106) by @sapphi-red - add `--configLoader=native` option (#10118) by @sapphi-red ### 🐛 Bug Fixes - improve invalid annotation warnings (#10185) by @hyf0 - keep deduplicated asset filenames stable once they can be observed (#10191) by @shulaoda - sourcemap_filenames: use public option name in pattern errors (#10188) by @IWANABETHATGUY - sourcemap_filenames: hash prepared sourcemap content (#10178) by @hyf0 - tree-shake unused circular declarators exported via export list (#10166) by @IWANABETHATGUY - dev: don't panic when an HMR rebuild hits an unresolved import (#10162) by @shulaoda - propagate errors from output.globals function (#9880) by @shulaoda - dev: revert cache mutations when a partial scan fails (#10110) by @shulaoda - dev: update importer relationships of cached modules in incremental build (#10107) by @shulaoda - hmr: fall back to full reload when a changed module is not registered as executed (#10132) by @shulaoda - chunk-optimizer: follow entry facade edges in runtime placement cycle check (#10101) by @hyf0 - dev: ignore watcher events after close (#10113) by @hyf0 - emit async wrapper for TLA modules under onDemandWrapping (#10086) by @IWANABETHATGUY - gate sideEffects:false modules' side effects on body demand (#10080) by @IWANABETHATGUY - rolldown_plugin_vite_resolve: return empty object for `browser: false` mapped modules (#10082) by @sapphi-red - reset the word-boundary state on newline in Hires::Boundary sourcemaps (#10025) by @shulaoda - trim an emptied chunk's outro/intro instead of skipping past it (#10029) by @shulaoda - test each edited chunk's own start against indent exclude ranges (#10026) by @shulaoda - preserve sourcemap mappings for indented lines when a CJS module shares the chunk (#10074) by @hyf0 ### 🚜 Refactor - separate tree-shaking side effects from execution order sensitivity (#10168) by @hyf0 - type construct_vite_preload_call to take an ObjectPattern (#10135) by @shulaoda - treeshake: single-source the own-export classification shared with the lazy-barrel loader (#10098) by @IWANABETHATGUY - dev: reuse Vite's bundledDev server (#10081) by @h-a-n-a - clippy: ban std HashMap/HashSet in favour of FxHashMap/FxHashSet (#10108) by @Boshen - treeshake: make body demand a second module bit instead of a stmt multimap (#10097) by @IWANABETHATGUY - seal used_symbol_refs by construction after its last writer (#10091) by @hyf0 - treeshake: replace inclusion mutual recursion with a worklist engine (#10096) by @IWANABETHATGUY - treeshake: split include_statements.rs into focused modules (#10095) by @IWANABETHATGUY - drop redundant is_user_defined filter on partitioned entries (#10050) by @shulaoda - project the retained export interface out of used_symbol_refs (#10089) by @hyf0 - track used external symbols separately from used_symbol_refs (#10088) by @hyf0 - make module namespace inclusion an explicit linking metadata field (#10087) by @hyf0 - rename statement evaluation metadata (#10078) by @hyf0 ### 📚 Documentation - virtual modules user-facing id convention (#10155) by @sapphi-red - cli: clarify disabling boolean/object flags like codeSplitting (#10153) by @IWANABETHATGUY - chore: remove Vite+ alpha banner (#10105) by @mdong1909 - write down the used_symbol_refs contract (#10090) by @hyf0 - dev/lazy: update design and implementation (#10079) by @h-a-n-a ### ⚡ Performance - ast_scanner: stop order-sensitivity checks once a module is flagged (#10190) by @IWANABETHATGUY - return impl ExactSizeIterator from slice-backed accessors (#10133) by @Boshen - binding: box dev and watcher napi futures (#10103) by @Boshen ### 🧪 Testing - move string_wizard replace unit tests to the JS magic-string suite (#10176) by @IWANABETHATGUY - dev: assert incremental scan state matches a fresh full build after each HMR step (#10115) by @shulaoda - dev: restore runtime assertions of delete_file_not_used_anymore (#10112) by @shulaoda - dev: fix flaky dev server tests in CI (#10152) by @h-a-n-a - add regression test for #10099 (lazyBarrel drops default-import binding but keeps its property reads) (#10109) by @IWANABETHATGUY ### ⚙️ Miscellaneous Tasks - deploy website to Void via GitHub OIDC (#10192) by @Boshen - deps: update oxc to 0.139.0 (#10161) by @shulaoda - deps: update test262 submodule for tests (#10160) by @rolldown-guard[bot] - rolldown_plugin_utils: remove dead asset-url and css scaffolding (#10131) by @shulaoda - deps: revert vite-plus to v0.2.1 (#10148) by @shulaoda - deps: update github actions (#10141) by @renovate[bot] - deps: update dependency rust to v1.96.1 (#10145) by @renovate[bot] - deps: update npm packages (#10142) by @renovate[bot] - deps: update rust crates (#10143) by @renovate[bot] - deps: update napi to v3.10.3 (#10121) by @renovate[bot] - rolldown_utils: remove unused time module (#10138) by @shulaoda - remove dead CopyModulePlugin::is_active method (#10129) by @shulaoda - remove dead LazyCompilationContext::is_lazy_module method (#10128) by @shulaoda - remove dead BuildDiagnostic::downcast_ref method (#10127) by @shulaoda - deps: update dependency vite-plus to v0.2.2 (#10084) by @renovate[bot] - deps: update rust crate oxc_sourcemap to v8.1.0 (#10122) by @renovate[bot] - deps: update crate-ci/typos action to v1.48.0 (#10124) by @renovate[bot] - enable more clippy restriction lints (#10114) by @Boshen - deps: update rust dependencies (#10100) by @Boshen - deps: update oxc resolver to v11.23.0 (#10083) by @renovate[bot] ###◀️ Revert - Revert "chore(deps): revert vite-plus to v0.2.1" (#10157) by @h-a-n-a - "fix(hmr): fall back to full reload when a changed module is not registered as executed (#10132)" (#10151) by @shulaoda ### ❤️ New Contributors * @V1OL3TF0X made their first contribution in [#9271](#9271) Co-authored-by: shulaoda <[email protected]>
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Description
Fixes #10165.
let f = () => {}, a = () => b(), b = () => a();followed byexport { f, a, b }kept the unuseda/bpair in the output, while the equivalent inline formexport let F = ..., A = ..., B = ...tree-shook them.Tree-shaking includes whole top-level statements. Before scanning, only exported multi-declarator declarations (and, under
keepNames, all of them) were split into one statement per declarator, so demanding one binding of a bare declaration kept every declarator in it. The default dce-only minify pass normally cleans up such leftovers, but it counts references and cannot delete two functions that reference each other in a cycle — so the circular pair survived.The fix splits bare top-level multi-declarator declarations in the pre-scan the same way exported ones already are (
split_multi_declaratorintweak_ast_for_scanning.rs), giving inclusion analysis per-declarator granularity. This matches esbuild, which creates one part per declarator.Two details:
Snapshot changes are cosmetic: joined declarations now print as separate statements (all their declarators are used), and two fixtures with mixed identifier/destructuring declarations print grouped again.
Alternatives explored
Test plan
crates/rolldown/tests/rolldown/issues/10165mirrors the issue (fails without the fix:a/bstay in the output) and asserts at runtime that a destructuring side effect next to an exported plain binding is preserved.cargo test --workspace: green (1797 integration tests), 9 cosmetic snapshot updates.just test-node-rolldown: green.