fix: treat namespace member access as side-effect-free#9099
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graphite-app[bot] merged 1 commit intomainfrom Apr 14, 2026
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fix: treat namespace member access as side-effect-free#9099graphite-app[bot] merged 1 commit intomainfrom
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@sapphi-red Is this pr enough for now? It’s a trade-off between peak performance and problem-solving efficiency, see |
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Yes, I think it's enough for now. |
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h-a-n-a
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hyf0
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hyf0
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Merging this PR will not alter performance
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## Summary - Treat property reads on ES module namespace objects (`import * as ns`) as side-effect-free, since namespace objects are frozen/sealed by spec with no getters - Track namespace import symbols in the AST scanner and pass them to the `SideEffectDetector` - This allows tree-shaking of unused exports whose initializers reference namespace member expressions (e.g. `ns.foo`), preventing unnecessary dynamic chunks from being emitted ## Limitation This optimization only applies to **direct** (one-level) namespace member access — e.g. `ns.foo` — not deeper chains like `ns.foo.bar`. For `ns.foo.bar`, the outer `.bar` access has `ns.foo` (a member expression) as its object, not the namespace identifier directly, so it won't be recognized as a namespace access. While `ns.foo` itself is side-effect-free, the value it returns could be any object with getters, so treating `ns.foo.bar` as side-effect-free would require knowing the type of the resolved export. Supporting deeper chains would require re-analyzing side effects after the `bind_imports_and_exports` phase, where member expressions are resolved to their target symbols through the module graph. This would add a second side-effect analysis pass, which has performance implications. The current single-level approach covers the most common patterns (like the reported issue) without requiring this additional pass. Closes #9061
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This was referenced Apr 15, 2026
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## [1.0.0-rc.16] - 2026-04-16 ### 🚀 Features - const enum cross-module inlining support (#8796) by @Dunqing - implement module tagging system for code splitting (#9045) by @hyf0 ### 🐛 Bug Fixes - rolldown_plugin_vite_manifest: handle duplicate chunk names for CSS entries (#9059) by @sapphi-red - improve error message for invalid return values in function options (#9125) by @shulaoda - await async export-star init wrappers (#9101) by @thezzisu - never panic during diagnostic emission (#9091) by @IWANABETHATGUY - include array rest pattern in binding_identifiers (#9112) by @IWANABETHATGUY - rolldown: set worker thread count with ROLLDOWN_WORKER_THREADS (#9086) by @fpotter - rolldown_plugin_lazy_compilation: escape request ID in proxy modules (#9102) by @h-a-n-a - treat namespace member access as side-effect-free (#9099) by @IWANABETHATGUY - relax overly conservative side-effect leak check in chunk optimizer (#9085) by @IWANABETHATGUY - runtime: release `cb` reference after `__commonJS` factory initialization (#9067) by @hyf0-agent - `@__NO_SIDE_EFFECTS__` wrapper should not remove dynamic imports (#9075) by @IWANABETHATGUY - rolldown_plugin_vite_import_glob: use POSIX path join/normalize for glob resolution (#9077) by @shulaoda - emit REQUIRE_TLA error when require() loads a module with top-level await (#9071) by @jaehafe - emit namespace declaration for empty modules in manual chunks (#8993) by @privatenumber - rolldown_plugin_vite_import_glob: keep common base on path segment boundary (#9070) by @shulaoda - prevent circular runtime helper imports during facade elimination (#8989) (#9057) by @IWANABETHATGUY - correct circular dependency check in facade elimination (#9047) by @h-a-n-a - docs: correct dead link in CodeSplittingGroup.tags JSDoc (#9051) by @hyf0 - emit DUPLICATE_SHEBANG warning when banner contains shebang (#9026) by @IWANABETHATGUY ### 🚜 Refactor - use semantic reference flags for member write detection (#9060) by @Dunqing - extract UsedSymbolRefs newtype wrapper (#9130) by @IWANABETHATGUY - dedupe await wrapping in export-star init emit (#9119) by @IWANABETHATGUY - calculate side-effect-free function symbols on demand (#9120) by @IWANABETHATGUY - extract duplicated top-level await handling into shared helper (#9087) by @IWANABETHATGUY - rolldown_plugin_vite_import_glob: use split_first for get_common_base (#9069) by @shulaoda - simplify ESM init deduplication with idiomatic insert check (#9044) by @IWANABETHATGUY ### 📚 Documentation - document runtime module placement strategy in code-splitting design (#9062) by @IWANABETHATGUY - clarify `options` hook behavior difference with Rollup in watch mode (#9053) by @sapphi-red - meta/design: introduce module tags (#9017) by @hyf0 ### ⚡ Performance - convert `generate_transitive_esm_init` to iterative (#9046) by @IWANABETHATGUY ### 🧪 Testing - merge strict/non_strict test variants using configVariants (#9089) by @IWANABETHATGUY ### ⚙️ Miscellaneous Tasks - disable Renovate auto-updates for oxc packages (#9129) by @IWANABETHATGUY - upgrade oxc@0.126.0 (#9127) by @Dunqing - deps: update napi to v3.8.5 (#9126) by @renovate[bot] - deps: update dependency @napi-rs/cli to v3.6.2 (#9123) by @renovate[bot] - move lazy-compilation design doc (#9117) by @h-a-n-a - deps: update dependency vite-plus to v0.1.18 (#9118) by @renovate[bot] - deps: update dependency vite-plus to v0.1.17 (#9113) by @renovate[bot] - deps: update oxc to v0.125.0 (#9094) by @renovate[bot] - deps: update dependency follow-redirects to v1.16.0 [security] (#9103) by @renovate[bot] - deps: update test262 submodule for tests (#9097) by @sapphi-red - deps: update crate-ci/typos action to v1.45.1 (#9096) by @renovate[bot] - deps: update rust crates (#9081) by @renovate[bot] - deps: update npm packages (#9080) by @renovate[bot] - remove outdated TODO in determine_module_exports_kind (#9072) by @jaehafe - rust/test: support `extendedTests: false` shorthand in test config (#9050) by @hyf0 - ci: extract shared infra-changes anchor in path filters (#9054) by @hyf0 - add docs build check to catch dead links in PRs (#9052) by @hyf0 ### ❤️ New Contributors * @thezzisu made their first contribution in [#9101](#9101) * @fpotter made their first contribution in [#9086](#9086) * @jaehafe made their first contribution in [#9071](#9071) * @privatenumber made their first contribution in [#8993](#8993) Co-authored-by: shulaoda <165626830+shulaoda@users.noreply.github.com>
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Summary
import * as ns) as side-effect-free, since namespace objects are frozen/sealed by spec with no gettersSideEffectDetectorns.foo), preventing unnecessary dynamic chunks from being emittedLimitation
This optimization only applies to direct (one-level) namespace member access — e.g.
ns.foo— not deeper chains likens.foo.bar.For
ns.foo.bar, the outer.baraccess hasns.foo(a member expression) as its object, not the namespace identifier directly, so it won't be recognized as a namespace access. Whilens.fooitself is side-effect-free, the value it returns could be any object with getters, so treatingns.foo.baras side-effect-free would require knowing the type of the resolved export.Supporting deeper chains would require re-analyzing side effects after the
bind_imports_and_exportsphase, where member expressions are resolved to their target symbols through the module graph. This would add a second side-effect analysis pass, which has performance implications. The current single-level approach covers the most common patterns (like the reported issue) without requiring this additional pass.Closes #9061