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fix(minifier): don't drop global calls that throw despite pure arguments#23917

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fix(minifier): don't drop global calls that throw despite pure arguments#23917
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fix/minifier-keep-throwing-global-calls

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@Dunqing Dunqing commented Jun 29, 2026

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What

is_pure_global_method_call (and the bare-global path) in CallExpression::may_have_side_effects treated a call as side-effect-free whenever its arguments were, ignoring that several of these functions throw at runtime. Unused calls that throw were therefore dropped as dead code. terser and esbuild both keep them.

Guard the cases oxc can prove:

Call Throws Before After
String.raw(), Symbol.keyFor(), Symbol.keyFor(42) TypeError (missing/invalid required arg) dropped kept
URL.canParse() TypeError (required first arg) dropped kept
String.fromCodePoint(-1 / 1.5 / 0x110000) RangeError (code point outside [0, 0x10FFFF]) dropped kept
Math.abs(10n), Date.UTC(10n), String.fromCharCode(10n), isNaN(10n), … TypeError (ToNumber(BigInt)) dropped kept

Safe optimizations are preserved — URL.canParse("x"), String.fromCodePoint(65), String.fromCharCode(65), Math.abs(1) still drop. String.raw / Symbol.keyFor are removed from the pure-method list (never provably safe); the rest get argument guards.

A Symbol argument is left droppable, on purpose

A Symbol argument also throws (ToString / ToNumber on a Symbol), but oxc has no ValueType::Symbol and to_primitive never resolves a pure expression to Symbol, so a Symbol throw is never provable. Guarding it would mean keeping every Math.abs(x) / parseInt(x) on an undetermined argument — a large minification regression. esbuild makes the same trade-off (it drops Math.abs(Symbol.iterator) too), so only the provable cases are guarded.

oxc already guards exactly this for the Number / Symbol / BigInt / Error constructors; this brings the method-call path in line. The assumption (including the non-provable-Symbol carve-out) is documented in crates/oxc_minifier/docs/ASSUMPTIONS.md.

Covered by test_throwing_global_calls in crates/oxc_minifier/tests/ecmascript/may_have_side_effects.rs; cross-checked against terser and esbuild; minsize unchanged.


Stacked on #23916.

Dunqing commented Jun 29, 2026

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@github-actions github-actions Bot added the A-minifier Area - Minifier label Jun 29, 2026
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Dunqing marked this pull request as ready for review June 29, 2026 02:08
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codspeed-hq Bot commented Jun 29, 2026

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Merging this PR will not alter performance

✅ 62 untouched benchmarks
⏩ 9 skipped benchmarks1


Comparing fix/minifier-keep-throwing-global-calls (695ed41) with main (dcc9a73)

Open in CodSpeed

Footnotes

  1. 9 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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Dunqing force-pushed the fix/minifier-keep-throwing-global-calls branch from e57aa0d to f4e61d1 Compare June 29, 2026 02:27
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graphite-app Bot changed the base branch from fix/minifier-object-isextensible-pure to graphite-base/23917 June 29, 2026 13:51
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graphite-app Bot force-pushed the fix/minifier-keep-throwing-global-calls branch from 45e0a0c to 695ed41 Compare June 29, 2026 13:56
@Dunqing Dunqing added the run-monitor-oxc Add to a PR to dispatch oxc-project/monitor-oxc CI against it label Jul 1, 2026
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@oxc-guard oxc-guard Bot removed the run-monitor-oxc Add to a PR to dispatch oxc-project/monitor-oxc CI against it label Jul 1, 2026
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Dunqing commented Jul 2, 2026

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…nts (#23917)

## What

`is_pure_global_method_call` (and the bare-global path) in `CallExpression::may_have_side_effects` treated a call as side-effect-free whenever its arguments were, ignoring that several of these functions **throw** at runtime. Unused calls that throw were therefore dropped as dead code. terser and esbuild both keep them.

Guard the cases oxc can prove:

| Call | Throws | Before | After |
| --- | --- | --- | --- |
| `String.raw()`, `Symbol.keyFor()`, `Symbol.keyFor(42)` | `TypeError` (missing/invalid required arg) | dropped | kept |
| `URL.canParse()` | `TypeError` (required first arg) | dropped | kept |
| `String.fromCodePoint(-1 / 1.5 / 0x110000)` | `RangeError` (code point outside `[0, 0x10FFFF]`) | dropped | kept |
| `Math.abs(10n)`, `Date.UTC(10n)`, `String.fromCharCode(10n)`, `isNaN(10n)`, … | `TypeError` (`ToNumber(BigInt)`) | dropped | kept |

Safe optimizations are preserved — `URL.canParse("x")`, `String.fromCodePoint(65)`, `String.fromCharCode(65)`, `Math.abs(1)` still drop. `String.raw` / `Symbol.keyFor` are removed from the pure-method list (never provably safe); the rest get argument guards.

### A Symbol argument is left droppable, on purpose

A Symbol argument also throws (`ToString` / `ToNumber` on a Symbol), but oxc has no `ValueType::Symbol` and `to_primitive` never resolves a pure expression to `Symbol`, so a Symbol throw is **never provable**. Guarding it would mean keeping every `Math.abs(x)` / `parseInt(x)` on an undetermined argument — a large minification regression. esbuild makes the same trade-off (it drops `Math.abs(Symbol.iterator)` too), so only the provable cases are guarded.

oxc already guards exactly this for the `Number` / `Symbol` / `BigInt` / `Error` constructors; this brings the method-call path in line. The assumption (including the non-provable-Symbol carve-out) is documented in `crates/oxc_minifier/docs/ASSUMPTIONS.md`.

Covered by `test_throwing_global_calls` in `crates/oxc_minifier/tests/ecmascript/may_have_side_effects.rs`; cross-checked against terser and esbuild; `minsize` unchanged.

---

Stacked on #23916.
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graphite-app Bot force-pushed the fix/minifier-keep-throwing-global-calls branch from 695ed41 to e274415 Compare July 2, 2026 02:02
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graphite-app Bot merged commit e274415 into main Jul 2, 2026
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@graphite-app graphite-app Bot removed the 0-merge Merge with Graphite Merge Queue label Jul 2, 2026
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graphite-app Bot deleted the fix/minifier-keep-throwing-global-calls branch July 2, 2026 02:06
camc314 pushed a commit that referenced this pull request Jul 3, 2026
…nts (#23917)

## What

`is_pure_global_method_call` (and the bare-global path) in `CallExpression::may_have_side_effects` treated a call as side-effect-free whenever its arguments were, ignoring that several of these functions **throw** at runtime. Unused calls that throw were therefore dropped as dead code. terser and esbuild both keep them.

Guard the cases oxc can prove:

| Call | Throws | Before | After |
| --- | --- | --- | --- |
| `String.raw()`, `Symbol.keyFor()`, `Symbol.keyFor(42)` | `TypeError` (missing/invalid required arg) | dropped | kept |
| `URL.canParse()` | `TypeError` (required first arg) | dropped | kept |
| `String.fromCodePoint(-1 / 1.5 / 0x110000)` | `RangeError` (code point outside `[0, 0x10FFFF]`) | dropped | kept |
| `Math.abs(10n)`, `Date.UTC(10n)`, `String.fromCharCode(10n)`, `isNaN(10n)`, … | `TypeError` (`ToNumber(BigInt)`) | dropped | kept |

Safe optimizations are preserved — `URL.canParse("x")`, `String.fromCodePoint(65)`, `String.fromCharCode(65)`, `Math.abs(1)` still drop. `String.raw` / `Symbol.keyFor` are removed from the pure-method list (never provably safe); the rest get argument guards.

### A Symbol argument is left droppable, on purpose

A Symbol argument also throws (`ToString` / `ToNumber` on a Symbol), but oxc has no `ValueType::Symbol` and `to_primitive` never resolves a pure expression to `Symbol`, so a Symbol throw is **never provable**. Guarding it would mean keeping every `Math.abs(x)` / `parseInt(x)` on an undetermined argument — a large minification regression. esbuild makes the same trade-off (it drops `Math.abs(Symbol.iterator)` too), so only the provable cases are guarded.

oxc already guards exactly this for the `Number` / `Symbol` / `BigInt` / `Error` constructors; this brings the method-call path in line. The assumption (including the non-provable-Symbol carve-out) is documented in `crates/oxc_minifier/docs/ASSUMPTIONS.md`.

Covered by `test_throwing_global_calls` in `crates/oxc_minifier/tests/ecmascript/may_have_side_effects.rs`; cross-checked against terser and esbuild; `minsize` unchanged.

---

Stacked on #23916.
Boshen added a commit that referenced this pull request Jul 6, 2026
### 🚀 Features

- 260425f semantic/examples: Include unresolved references (#24214)
(camc314)
- 2d9b0b3 minifier: Fold boolean-literal ternary branches in value
contexts (#24110) (Dunqing)
- 61fbf10 ast: Implement `ReplaceWith` on all AST types (#24013)
(overlookmotel)
- 7db7a29 allocator: Add `ReplaceWith` trait (#24012) (overlookmotel)
- 4eb074e mangler: Add `reserved` option for names that must not be
mangled (#24041) (Dunqing)
- 2e62012 data_structures: Add `StringExt` trait (#24006)
(overlookmotel)
- 60e7160 minifier: Drop side-effect-free IIFEs whose result is unused
(#23967) (Dunqing)
- 26dd9e2 ast: Add method to widen inherited enum ref to parent ref
(#23961) (overlookmotel)

### 🐛 Bug Fixes

- e8b50ee transformer: Clean up semantics for stripped TypeScript syntax
(#24180) (camc314)
- d966d0b react_compiler: Remove clippy allows (#24168) (Boshen)
- 854ef8d react_compiler: Compile generic functions instead of
over-bailing on type-param hoisting (#24158) (Boshen)
- 093586c react_compiler: Align memoization cache-slot allocation with
Babel (#24157) (Boshen)
- 09c8f59 react_compiler: Normalize snapshot fixture paths (#24142)
(camc314)
- f13df97 react_compiler: Drop stray empty statement from catch bindings
(#24133) (Boshen)
- cb2a505 react_compiler: Codegen destructuring reassignment targets
(#24131) (Boshen)
- b82c394 react_compiler: Propagate codegen invariants instead of
emitting empty bodies (#24128) (Boshen)
- 5771982 react_compiler: Render unchanged programs as source in fixture
snapshots (#24129) (Boshen)
- 4b16e1a transformer/async-to-generator: Preserve direct eval scope
flags (#24136) (camc314)
- 4e9194f react_compiler: Lower `delete obj.prop` to
Property/ComputedDelete (#24123) (Boshen)
- 0b25582 ast: Type binding node `typeAnnotation` as `TSTypeAnnotation |
null` (#23113) (Boshen)
- 018c0e5 transformer: Hoist lowered async declarations (#22770)
(camc314)
- 652fbaf mangler: Keep names of destructured exported bindings (#24036)
(Dunqing)
- e274415 minifier: Don't drop global calls that throw despite pure
arguments (#23917) (Dunqing)
- 59abb30 minifier: Only merge string literals in `try_fold_add` when
the inner operator is `+` (#23622) (Jerry Zhao)

### ⚡ Performance

- c5ca77b transformer: Avoid cloning refresh options (#24191) (camc314)
- bf1a151 react_compiler: Compile out debug printers (#24184) (Boshen)
- abb44a0 transformer: Build fixed object-rest arguments (#24190)
(camc314)
- a4db731 isolated_declarations: Use `ReplaceWith` instead of `TakeIn`
(#24016) (overlookmotel)
- ff10855 transformer: Use `ReplaceWith` instead of `TakeIn` (#24015)
(overlookmotel)
- bd49aff ecmascript: Avoid heap-allocating Math.min/max/imul operands
(#23941) (Lawrence Lin)
- e4b708b react_compiler: Skip compiled files before prefilters (#24171)
(Boshen)
- c59f2fe rust: Return impl ExactSizeIterator from slice-backed
accessors (#24144) (Boshen)
- 5d6d04a codegen: SWAR-skip boring byte runs in sourcemap line/column
scan (#24023) (Boshen)
- a55e0be traverse: Reduce string operations in `get_var_name_from_node`
(#24007) (overlookmotel)
- e6d48e1 transformer/nullish_coalescing: Move cold path into separate
function (#23989) (overlookmotel)
- c4e35b5 transformer/object_rest_spread: Pre-allocate capacity in `Vec`
(#23988) (overlookmotel)
- 527b8e5 transformer/decorators: Narrow type earlier (#23987)
(overlookmotel)

### 📚 Documentation

- 30d17f5 allocator: Clarify docs for `TakeIn::take_in_box` (#24093)
(overlookmotel)
- 675e6a8 ast: Correct doc comment for `PrivateFieldExpression` (#24008)
(overlookmotel)
- e4c30e6 minifier: Explain what `dce` mode means (#23994) (Dunqing)
- 37cbf88 ast_macros: Document fields of `StructDetails` (#23959)
(overlookmotel)
- 4de3e54 ast: Correct doc comment (#23948) (overlookmotel)

Co-authored-by: Boshen <[email protected]>
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