feat(minifier): disable removal of unnecessary `use strict` directives for DCE #15691

sapphi-red · 2025-11-14T10:16:53Z

This is kind of a workaround. The target of this PR is to solve rolldown/rolldown#6879 and rolldown/rolldown#6880.

While the proper way to fix them is to use the proper ModuleKind (described in rolldown/rolldown#7009), ModuleKind::Unambiguous doesn't work as expected and is blocked by #15541.

So for the meanwhile, this PR can solve those issues indirectly. We can revert this PR once the issues above are solved properly, but I guess it's also fine to keep it as I think there's less value to remove use strict directives in DCE.

sapphi-red · 2025-11-14T10:17:07Z

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codspeed-hq · 2025-11-14T10:22:03Z

CodSpeed Performance Report

Merging #15691 will not alter performance

_{Comparing 11-14-feat_minifier_disable_removal_of_unnecessary_use_strict_directives_for_dce (87657e1) with main (d493d78)¹}

Summary

✅ 33 untouched
⏩ 4 skipped²

No successful run was found on main (7c4a916) during the generation of this report, so d493d78 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩
4 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

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Pull Request Overview

This PR introduces a configuration option to disable the removal of unnecessary use strict directives during Dead Code Elimination (DCE). This is a workaround for rolldown issues #6879 and #6880 until proper ModuleKind handling is implemented.

Key changes:

Added remove_unnecessary_use_strict boolean flag to NormalizeOptions
DCE path now preserves use strict directives while the regular compressor still removes them
Added test coverage to ensure use strict directives are preserved during DCE

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
`crates/oxc_minifier/src/peephole/normalize.rs`	Added new `remove_unnecessary_use_strict` option to `NormalizeOptions` struct and conditionally applied it in `exit_program` and `exit_function_body` methods
`crates/oxc_minifier/src/compressor.rs`	Configured the new option: `true` for regular compression and `false` for DCE
`crates/oxc_minifier/tests/peephole/dead_code_elimination.rs`	Added test case to verify `use strict` directives are preserved during DCE

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Boshen · 2025-11-15T03:40:30Z

Merge activity

Nov 15, 3:40 AM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
Nov 15, 3:40 AM UTC: Boshen added this pull request to the Graphite merge queue.
Nov 15, 3:46 AM UTC: Merged by the Graphite merge queue.

…s for DCE (#15691) This is kind of a workaround. The target of this PR is to solve rolldown/rolldown#6879 and rolldown/rolldown#6880. While the proper way to fix them is to use the proper `ModuleKind` (described in rolldown/rolldown#7009), `ModuleKind::Unambiguous` doesn't work as expected and is blocked by #15541. So for the meanwhile, this PR can solve those issues indirectly. We can revert this PR once the issues above are solved properly, but I guess it's also fine to keep it as I think there's less value to remove `use strict` directives in DCE.

### 💥 BREAKING CHANGES - ea51b0b napi: [**BREAKING**] Standardize function naming with sync suffixes (#15661) (Boshen) ### 🚀 Features - 77efb76 parser: Improve error message for invalid switch clauses (#15728) (sapphi-red) - 5691727 parser: Improve `import source` `from` error message (#15727) (sapphi-red) - b7404bc parser: Improve error message for missing function body (#15726) (sapphi-red) - 71c2fb0 parser: Improve error message when JSX is found while not enabled (#15725) (sapphi-red) - 56e7e44 minifier: Disable removal of unnecessary `use strict` directives for DCE (#15691) (sapphi-red) - 8a61cfd allocator, ast: Introduce `UnstableAddress` trait (#15700) (overlookmotel) - f5ce55a napi: Export all options using wildcard exports (Boshen) - 68703b9 minifier: Rotate binary expressions to remove parentheses (#15473) (sapphi-red) ### 🐛 Bug Fixes - c023ba6 semantic: Do not duplicate statements in temp `Vec` when binding `TSModuleDeclaration`s (#15724) (overlookmotel) - d60ca81 parser: Reject `import something 'source'` (#15746) (sapphi-red) - e0728fa ast: Exclude comment end position from `is_inside_comment` check (#15753) (camc314) - 9f54a36 semantic: Error on `\00` in strict mode (#15743) (sapphi-red) - 440a977 ast: Include rest properties when using `get_binding_identifiers` (#15710) (camc314) ### ⚡ Performance - 1f09d3c parser: Faster checking for invalid modifiers (#15717) (overlookmotel) - d8d4e31 ast: Use loop instead of recursion in `TSModuleDeclarationBody::as_module_block_mut` (#15713) (overlookmotel) ### 📚 Documentation - e033d50 ast: Clarify behavior of `TSModuleDeclaration::has_use_strict_directive` (#15730) (overlookmotel) - 9eda70f allocator: Improve docs for `Address` methods (#15697) (overlookmotel)

…s for DCE (oxc-project#15691) This is kind of a workaround. The target of this PR is to solve rolldown/rolldown#6879 and rolldown/rolldown#6880. While the proper way to fix them is to use the proper `ModuleKind` (described in rolldown/rolldown#7009), `ModuleKind::Unambiguous` doesn't work as expected and is blocked by oxc-project#15541. So for the meanwhile, this PR can solve those issues indirectly. We can revert this PR once the issues above are solved properly, but I guess it's also fine to keep it as I think there's less value to remove `use strict` directives in DCE.

### 💥 BREAKING CHANGES - ea51b0b napi: [**BREAKING**] Standardize function naming with sync suffixes (oxc-project#15661) (Boshen) ### 🚀 Features - 77efb76 parser: Improve error message for invalid switch clauses (oxc-project#15728) (sapphi-red) - 5691727 parser: Improve `import source` `from` error message (oxc-project#15727) (sapphi-red) - b7404bc parser: Improve error message for missing function body (oxc-project#15726) (sapphi-red) - 71c2fb0 parser: Improve error message when JSX is found while not enabled (oxc-project#15725) (sapphi-red) - 56e7e44 minifier: Disable removal of unnecessary `use strict` directives for DCE (oxc-project#15691) (sapphi-red) - 8a61cfd allocator, ast: Introduce `UnstableAddress` trait (oxc-project#15700) (overlookmotel) - f5ce55a napi: Export all options using wildcard exports (Boshen) - 68703b9 minifier: Rotate binary expressions to remove parentheses (oxc-project#15473) (sapphi-red) ### 🐛 Bug Fixes - c023ba6 semantic: Do not duplicate statements in temp `Vec` when binding `TSModuleDeclaration`s (oxc-project#15724) (overlookmotel) - d60ca81 parser: Reject `import something 'source'` (oxc-project#15746) (sapphi-red) - e0728fa ast: Exclude comment end position from `is_inside_comment` check (oxc-project#15753) (camc314) - 9f54a36 semantic: Error on `\00` in strict mode (oxc-project#15743) (sapphi-red) - 440a977 ast: Include rest properties when using `get_binding_identifiers` (oxc-project#15710) (camc314) ### ⚡ Performance - 1f09d3c parser: Faster checking for invalid modifiers (oxc-project#15717) (overlookmotel) - d8d4e31 ast: Use loop instead of recursion in `TSModuleDeclarationBody::as_module_block_mut` (oxc-project#15713) (overlookmotel) ### 📚 Documentation - e033d50 ast: Clarify behavior of `TSModuleDeclaration::has_use_strict_directive` (oxc-project#15730) (overlookmotel) - 9eda70f allocator: Improve docs for `Address` methods (oxc-project#15697) (overlookmotel)

github-actions bot added the A-minifier Area - Minifier label Nov 14, 2025

github-actions bot added the C-enhancement Category - New feature or request label Nov 14, 2025

sapphi-red requested a review from Boshen November 14, 2025 10:23

sapphi-red assigned Boshen Nov 14, 2025

sapphi-red marked this pull request as ready for review November 14, 2025 14:35

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Boshen added the 0-merge Merge with Graphite Merge Queue label Nov 15, 2025

graphite-app bot force-pushed the 11-14-feat_minifier_disable_removal_of_unnecessary_use_strict_directives_for_dce branch from 87657e1 to 56e7e44 Compare November 15, 2025 03:40

graphite-app bot merged commit 56e7e44 into main Nov 15, 2025
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graphite-app bot deleted the 11-14-feat_minifier_disable_removal_of_unnecessary_use_strict_directives_for_dce branch November 15, 2025 03:46

graphite-app bot removed the 0-merge Merge with Graphite Merge Queue label Nov 15, 2025

sapphi-red mentioned this pull request Nov 15, 2025

feat(minify): add directives option #15690

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Boshen mentioned this pull request Nov 17, 2025

release(crates): oxc v0.98.0 #15771

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feat(minifier): disable removal of unnecessary `use strict` directives for DCE #15691

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sapphi-red commented Nov 14, 2025 •

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Merging #15691 will not alter performance

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feat(minifier): disable removal of unnecessary `use strict` directives for DCE #15691

feat(minifier): disable removal of unnecessary `use strict` directives for DCE #15691

sapphi-red commented Nov 14, 2025 •

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