fix(rolldown): remove empty common chunks for advanced chunking#9550
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aminpaks wants to merge 2 commits into
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fix(rolldown): remove empty common chunks for advanced chunking#9550aminpaks wants to merge 2 commits into
aminpaks wants to merge 2 commits into
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Add graph-level empty common chunk elimination for advanced chunking.\n\n- Remove only non-entry common JS/TS chunks made entirely of metadata-confirmed re-export barrels.\n- Preserve chunks that import CSS so asset/hash ownership stays intact.\n- Retarget importer chunks to any side-effect chunks those barrels forwarded.\n- Treat no-replacement pure barrels as renderless unassigned modules in downstream passes.\n- Document the optimizer boundary.
Add rolldown#6677 regression coverage separately from the implementation.\n\n- Cover empty common chunk removal for side-effect and pure-barrel cases.\n- Keep barrels emitted when they are dynamic import targets.\n- Keep chunks that anchor external imports, CommonJS wrappers, or runtime-helper state.\n- Snapshot output so future guard changes cannot silently delete unsafe chunks.
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Manual/advanced chunking could leave a barrel module in its own common chunk after its re-export declarations resolved to symbols in other chunks. The chunk rendered as an empty JS file, but entry chunks still imported it.
This adds an empty-common-chunk optimization that removes only graph-proven ESM re-export facades. Before marking the chunk removed, the optimizer retargets importers to any live side-effectful dependencies forwarded through the removed chunk, so load-order side effects are preserved without source-string re-export detection.
Related: #8625 is an earlier attempt at the same #6677 issue. This PR takes a graph-level approach so chunk removal can stay conservative around side effects, dynamic imports, runtime helpers, CJS wrappers, externals, and CSS-owning modules.
Fixes #6677.
Disclosure: AI tools assisted with investigation and implementation. I reviewed, tested, and take responsibility for the submitted changes.