fix(ecmascript): enhance side-effect detection for classes, TypedArrays, computed members, and spread by Dunqing · Pull Request #20213 · oxc-project/oxc

Dunqing · 2026-03-11T03:01:39Z

Summary

Part of #19673

Several side-effect detection improvements:

Computed member expressions: When property_read_side_effects is None, non-literal keys (e.g. obj[identRef]) now check the key expression and object for their own side effects instead of always returning true
ObjectExpression spread: When property_read_side_effects is None, {...expr} delegates to the argument's own side effects
Class MethodDefinition: Now checks for parameter decorators (TypeScript @foo on params)
Class AccessorProperty: Now checks accessor property values for side effects
TypedArray constructors: Added Int8Array, Uint8Array, Uint8ClampedArray, Int16Array, Uint16Array, Int32Array, Uint32Array, Float32Array, Float64Array, BigInt64Array, BigUint64Array to pure constructors (DataView excluded as it requires an ArrayBuffer argument)

Test plan

Added tests for computed member non-literal keys with property_read_side_effects
Added tests for ObjectExpression spread with property_read_side_effects
Added tests for class method parameter decorators
Added tests for class accessor property values
Added tests for TypedArray constructors
All existing tests pass

🤖 Generated with Claude Code

Copilot

Pull request overview

Improves may_have_side_effects accuracy in oxc_ecmascript (used by the minifier/DCE) for additional ECMAScript/TypeScript constructs and expands test coverage to prevent regressions.

Changes:

Refines side-effect detection for computed member expressions and object spread when property_read_side_effects == None.
Extends class-element handling (method parameter decorators, accessor property initializers).
Treats TypedArray constructors as pure (and adds minifier tests for the new cases).

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
crates/oxc_minifier/tests/ecmascript/may_have_side_effects.rs	Adds regression tests for computed members, object spread, TS parameter decorators, accessor initializers, and TypedArray constructors.
crates/oxc_ecmascript/src/side_effects/expressions.rs	Updates side-effect logic for object spread/computed members/class elements; expands pure constructors; introduces `AssignmentExpression`/`UpdateExpression` handling.
crates/oxc_ecmascript/src/side_effects/context.rs	Adds a `property_write_side_effects()` hook to the side-effects context.

crates/oxc_ecmascript/src/side_effects/context.rs

crates/oxc_ecmascript/src/side_effects/expressions.rs

Dunqing · 2026-03-11T03:06:23Z

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codspeed-hq · 2026-03-11T03:08:13Z

Merging this PR will not alter performance

✅ 53 untouched benchmarks
⏩ 3 skipped benchmarks¹

_{Comparing fix/computed-member-spread-side-effects (988d663) with fix/known-globals-side-effects (4c397f0)²}

3 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. ↩
No successful run was found on fix/known-globals-side-effects (4d3b18e) during the generation of this report, so 63f714d was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

crates/oxc_ecmascript/src/side_effects/expressions.rs

Boshen · 2026-03-12T07:57:28Z

Merge activity

Mar 12, 7:57 AM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
Mar 12, 9:18 AM UTC: Boshen added this pull request to the Graphite merge queue.
Mar 12, 9:34 AM UTC: Merged by the Graphite merge queue.

…ys, computed members, and spread (#20213) ## Summary Part of #19673 Several side-effect detection improvements: - **Computed member expressions**: When `property_read_side_effects` is `None`, non-literal keys (e.g. `obj[identRef]`) now check the key expression and object for their own side effects instead of always returning `true` - **ObjectExpression spread**: When `property_read_side_effects` is `None`, `{...expr}` delegates to the argument's own side effects - **Class MethodDefinition**: Now checks for parameter decorators (TypeScript `@foo` on params) - **Class AccessorProperty**: Now checks accessor property values for side effects - **TypedArray constructors**: Added `Int8Array`, `Uint8Array`, `Uint8ClampedArray`, `Int16Array`, `Uint16Array`, `Int32Array`, `Uint32Array`, `Float32Array`, `Float64Array`, `BigInt64Array`, `BigUint64Array` to pure constructors (`DataView` excluded as it requires an `ArrayBuffer` argument) ## Test plan - [x] Added tests for computed member non-literal keys with `property_read_side_effects` - [x] Added tests for ObjectExpression spread with `property_read_side_effects` - [x] Added tests for class method parameter decorators - [x] Added tests for class accessor property values - [x] Added tests for TypedArray constructors - [x] All existing tests pass 🤖 Generated with [Claude Code](https://claude.com/claude-code)

### 🚀 Features - e7163b6 ecmascript: Add known-globals to side-effect-free property reads (#20212) (Dunqing) - 139ab68 ecmascript: Add `property_write_side_effects` to `MayHaveSideEffectsContext` (#20217) (Dunqing) ### 🐛 Bug Fixes - 78c264a parser: Fix conditional expressions with arrow-function alternates in TS (#20356) (camc314) - 5c97b14 minifier: Recognize object spread of object literals as side-effect-free (#20299) (Boshen) - 1ff5c1d transformer/typescript: Rewrite extensions in dynamic `import()` expressions (#20121) (Sverre Johansen) - 1c07b3b diagnostics: Handle `WouldBlock` in stdout writes to prevent panic (#20295) (Boshen) - ade14d4 ecmascript: Enhance side-effect detection for classes, TypedArrays, computed members, and spread (#20213) (Dunqing) ### ⚡ Performance - 5474d0a semantic: V8-style walk-up reference resolution (#20292) (Boshen) ### 📚 Documentation - e4aa5b5 parser/napi, linter/plugins: Add JSDoc comments to raw transfer constants (#20286) (overlookmotel) Co-authored-by: Boshen <1430279+Boshen@users.noreply.github.com>

Copilot AI review requested due to automatic review settings March 11, 2026 03:01

github-actions bot added A-minifier Area - Minifier C-bug Category - Bug labels Mar 11, 2026

Copilot started reviewing on behalf of Dunqing March 11, 2026 03:02 View session

Copilot AI reviewed Mar 11, 2026

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crates/oxc_ecmascript/src/side_effects/context.rs Outdated Show resolved Hide resolved

crates/oxc_ecmascript/src/side_effects/expressions.rs Outdated Show resolved Hide resolved

crates/oxc_ecmascript/src/side_effects/expressions.rs Outdated Show resolved Hide resolved

Dunqing changed the base branch from main to graphite-base/20213 March 11, 2026 03:05

Dunqing force-pushed the fix/computed-member-spread-side-effects branch from 1fe424a to f0ccc25 Compare March 11, 2026 03:06

Dunqing changed the base branch from graphite-base/20213 to fix/known-globals-side-effects March 11, 2026 03:06

Dunqing mentioned this pull request Mar 11, 2026

feat(ecmascript): add known-globals to side-effect-free property reads #20212

Merged

5 tasks

Dunqing force-pushed the fix/known-globals-side-effects branch from 8f68e8b to 411b61a Compare March 11, 2026 04:22

Dunqing force-pushed the fix/computed-member-spread-side-effects branch from f0ccc25 to 3599797 Compare March 11, 2026 04:22

Dunqing force-pushed the fix/known-globals-side-effects branch 3 times, most recently from 3089aca to cacff2f Compare March 11, 2026 04:42

Dunqing force-pushed the fix/computed-member-spread-side-effects branch from 3599797 to e39ffe3 Compare March 11, 2026 04:42

Dunqing mentioned this pull request Mar 11, 2026

feat(ecmascript): add property_write_side_effects to MayHaveSideEffectsContext #20217

Merged

2 tasks

Dunqing requested review from Boshen and sapphi-red March 12, 2026 05:36

Dunqing force-pushed the fix/known-globals-side-effects branch from cacff2f to 4c397f0 Compare March 12, 2026 05:57

Dunqing force-pushed the fix/computed-member-spread-side-effects branch from 01cb8fd to 1a433a8 Compare March 12, 2026 05:57

sapphi-red approved these changes Mar 12, 2026

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crates/oxc_ecmascript/src/side_effects/expressions.rs Show resolved Hide resolved

Dunqing force-pushed the fix/computed-member-spread-side-effects branch from 1a433a8 to 988d663 Compare March 12, 2026 06:57

Dunqing force-pushed the fix/known-globals-side-effects branch from 4c397f0 to 4d3b18e Compare March 12, 2026 06:58

Dunqing changed the base branch from fix/known-globals-side-effects to graphite-base/20213 March 12, 2026 07:33

Dunqing force-pushed the fix/computed-member-spread-side-effects branch from 988d663 to 1b9c059 Compare March 12, 2026 07:34

Dunqing force-pushed the graphite-base/20213 branch from 4d3b18e to 4d6a096 Compare March 12, 2026 07:34

Dunqing changed the base branch from graphite-base/20213 to fix/known-globals-side-effects March 12, 2026 07:34

Boshen added the 0-merge Merge with Graphite Merge Queue label Mar 12, 2026

Dunqing force-pushed the fix/known-globals-side-effects branch from 4d6a096 to d12655d Compare March 12, 2026 09:05

Dunqing force-pushed the fix/computed-member-spread-side-effects branch from 1b9c059 to 5b8ac85 Compare March 12, 2026 09:05

graphite-app bot force-pushed the fix/known-globals-side-effects branch from c4c894c to e7163b6 Compare March 12, 2026 09:23

graphite-app bot force-pushed the fix/computed-member-spread-side-effects branch from 0a97c72 to ade14d4 Compare March 12, 2026 09:23

Base automatically changed from fix/known-globals-side-effects to main March 12, 2026 09:34

graphite-app bot merged commit ade14d4 into main Mar 12, 2026
22 checks passed

graphite-app bot deleted the fix/computed-member-spread-side-effects branch March 12, 2026 09:34

graphite-app bot removed the 0-merge Merge with Graphite Merge Queue label Mar 12, 2026

Boshen mentioned this pull request Mar 14, 2026

release(crates): oxc v0.119.0 #20371

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fix(ecmascript): enhance side-effect detection for classes, TypedArrays, computed members, and spread#20213

fix(ecmascript): enhance side-effect detection for classes, TypedArrays, computed members, and spread#20213
graphite-app[bot] merged 1 commit intomainfrom
fix/computed-member-spread-side-effects

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Dunqing commented Mar 11, 2026

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Merging this PR will not alter performance

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