Detect variable reassignments in modules without side effects #5658
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Thank you for your contribution! ❤️You can try out this pull request locally by installing Rollup via npm install rollup/rollup#gh-5650_treeshake_module_side_effects_bugNotice: Ensure you have installed the latest stable Rust toolchain. If you haven't installed it yet, please see https://www.rust-lang.org/tools/install to learn how to download Rustup and install Rust. or load it into the REPL: |
This was referenced Sep 18, 2024
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Codecov ReportAll modified and coverable lines are covered by tests ✅
Additional details and impacted files@@ Coverage Diff @@
## master #5658 +/- ##
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Coverage 99.39% 99.39%
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Files 242 242
Lines 9345 9348 +3
Branches 2470 2470
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+ Hits 9288 9291 +3
Misses 48 48
Partials 9 9 ☔ View full report in Codecov by Sentry. |
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lukastaegert
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It appears that this might cause some build failures that need further investigation.
lukastaegert
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It appears that this might cause some build failures that need further investigation.
This was referenced Oct 13, 2024
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moduleSideEffects: falseremoves side effectful getter inside a exported function since 4.9.2 #5408Description
The bug was quite intricate:
This took me quite some thinking to fix. The problem is that while the contract of
moduleSideEffects: falsemeans that we check the module for side-effectful code if at least one export is used, there are situations in Rollup where we "use" an export without including it in the bundle.To mitigate this, accessing an identifier during tree-shaking will now always mark the module as "potentially included", overriding the moduleSideEffects flag, because obviously we used a variable of that module.
To not break a previous fix around TDZ detection, I needed to rework this slightly as well: Now modules are marked when they receive a proper tree-shaking pass and if we use a variable from a module that did not receive a pass, we do not perform TDZ detection for that variable as the logic would be faulty.