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fix(mangler): keep names of destructured exported bindings#24036

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fix/mangler-destructured-exports
Jul 2, 2026
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fix(mangler): keep names of destructured exported bindings#24036
graphite-app[bot] merged 1 commit into
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fix/mangler-destructured-exports

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@Dunqing

@Dunqing Dunqing commented Jul 2, 2026

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collect_exported_symbols resolved each exported variable declarator with get_binding_identifier, which returns None for destructuring patterns — so the bindings of export const { … } = … were never marked as exported and got mangled, renaming the module's named exports. Collect the declarator's bound_names instead, which covers object / array patterns, nesting, defaults and rest elements.

Surfaced by the monitor-oxc mangler runtime test (previously masked by the idempotency failures fixed in #24033): mangled css-tree lost its find export and @asamuzakjp/dom-selector failed with SyntaxError: The requested module 'css-tree' does not provide an export named 'find' (failing run). The same export shape appears in commander, csso, colorette, ansis and @actions/io, so those were broken too.

Example

import syntax from "./syntax/index.js";
export const { tokenize, parse, find } = syntax;

Before:

import e from "./syntax/index.js";
export const { tokenize: t, parse: n, find: s } = e; // exports `t`, `n`, `s`

After:

import e from "./syntax/index.js";
export const { tokenize, parse, find } = e;

Verified end-to-end by mangling every file in [email protected] and exercising import { find, parse, generate, walk } from "css-tree" in node.

Dunqing commented Jul 2, 2026

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@github-actions github-actions Bot added the A-minifier Area - Minifier label Jul 2, 2026
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Merging this PR will not alter performance

✅ 62 untouched benchmarks
⏩ 9 skipped benchmarks1


Comparing fix/mangler-destructured-exports (c06a9a2) with main (68e724a)

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.

@Dunqing
Dunqing requested a review from sapphi-red July 2, 2026 05:43
@Dunqing
Dunqing marked this pull request as ready for review July 2, 2026 05:43
@Dunqing Dunqing added the 0-merge Merge with Graphite Merge Queue label Jul 2, 2026

Dunqing commented Jul 2, 2026

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`collect_exported_symbols` resolved each exported variable declarator with `get_binding_identifier`, which returns `None` for destructuring patterns — so the bindings of `export const { … } = …` were never marked as exported and got mangled, **renaming the module's named exports**. Collect the declarator's `bound_names` instead, which covers object / array patterns, nesting, defaults and rest elements.

Surfaced by the monitor-oxc mangler runtime test (previously masked by the idempotency failures fixed in #24033): mangled `css-tree` lost its `find` export and `@asamuzakjp/dom-selector` failed with `SyntaxError: The requested module 'css-tree' does not provide an export named 'find'` ([failing run](https://github.com/oxc-project/monitor-oxc/actions/runs/28562614557/job/84683456673)). The same export shape appears in commander, csso, colorette, ansis and `@actions/io`, so those were broken too.

## Example

```js
import syntax from "./syntax/index.js";
export const { tokenize, parse, find } = syntax;
```

Before:

```js
import e from "./syntax/index.js";
export const { tokenize: t, parse: n, find: s } = e; // exports `t`, `n`, `s`
```

After:

```js
import e from "./syntax/index.js";
export const { tokenize, parse, find } = e;
```

Verified end-to-end by mangling every file in `[email protected]` and exercising `import { find, parse, generate, walk } from "css-tree"` in node.
@graphite-app
graphite-app Bot force-pushed the fix/mangler-destructured-exports branch from c06a9a2 to 652fbaf Compare July 2, 2026 05:51
@graphite-app
graphite-app Bot merged commit 652fbaf 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
@graphite-app
graphite-app Bot deleted the fix/mangler-destructured-exports branch July 2, 2026 05:55

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LGTM

graphite-app Bot pushed a commit that referenced this pull request Jul 2, 2026
…ed (#24041)

Adds `MangleOptions::reserved` — equivalent to terser / uglify-js / swc `mangle.reserved`: names in the set are never used as mangled names, and bindings that already carry them keep them. Default empty; default output is byte-identical to main (minsize snapshot unchanged).

## Motivation

Node's cjs-module-lexer detects a CommonJS module's named exports by **lexically** scanning for `exports.<name> =` / `module.exports` token patterns — no scope analysis ([its README documents renamed identifiers as "DETECTS: NO EXPORTS"](https://github.com/nodejs/cjs-module-lexer)). UMD / CommonJS wrappers bind `exports` / `module` as ordinary function parameters, and the mangler renames them, erasing every named export the lexer can see.

Surfaced by the monitor-oxc mangler runtime test ([failing run](https://github.com/oxc-project/monitor-oxc/actions/runs/28569108563/job/84702922472), previously masked by #24033 / #24036): `archiver` does `import { queue } from "async"`, and `async`'s dist is a UMD bundle — mangled, the factory parameter `exports` became `e` and node fails with `Named export 'queue' not found`. With `reserved: ["exports", "module"]` the output imports correctly (verified end-to-end in node, including running a queue task).

## Why an opt-in list instead of always keeping these names

Renaming them is ecosystem-standard. Verified empirically — minifying the same UMD sample and importing it in node:

| minifier | renames `exports` param? | `import { queue }` from its output | escape hatch |
| --- | --- | --- | --- |
| terser 5.48 | yes | fails | `mangle.reserved` (verified working) |
| uglify-js 3.19 | yes | fails | `reserved` (verified working) |
| esbuild 0.28 `--minify` | yes | fails | none for identifier mangling |
| swc | yes | fails | terser-style `mangle.reserved` ([swc#3424](swc-project/swc#3424)) |

An earlier revision of this PR kept `exports` / `module` unconditionally; the Minification Size check showed the real cost: ~1% minified on UMD-heavy files (d3: +3.3 kB from ~590 `exports` references, flipping it to *larger than esbuild*), because the point is keeping the literal 7-char token at every export site. No other minifier pays this by default — and rolldown bundles bind `exports` / `module` in every CJS interop wrapper, where node's lexer never looks. So oxc gets the same escape hatch as terser/swc, with the same name.

`MangleOptions` loses `Copy` (it now holds the set); construction sites switch to `..MangleOptions::default()` / `clone()`. Exposed in `oxc-minify` NAPI options (`mangle.reserved: string[]`) and the mangler example (`--reserve-exports`).

monitor-oxc will pass `["exports", "module"]` for its mangler runtime test (its corpus imports prebuilt CJS/UMD dists directly).

For reference, esbuild solves this for its *own* node-platform CJS bundles differently — a dead-code annotation `0 && (module.exports = { a, b })` that cjs-module-lexer recognizes ([esbuild#960](evanw/esbuild#960), [cjs-module-lexer#44](nodejs/cjs-module-lexer#44)); verified that pattern also works appended to fully-mangled output. That could be a future zero-size-cost alternative at the minifier level.
camc314 pushed a commit that referenced this pull request Jul 3, 2026
`collect_exported_symbols` resolved each exported variable declarator with `get_binding_identifier`, which returns `None` for destructuring patterns — so the bindings of `export const { … } = …` were never marked as exported and got mangled, **renaming the module's named exports**. Collect the declarator's `bound_names` instead, which covers object / array patterns, nesting, defaults and rest elements.

Surfaced by the monitor-oxc mangler runtime test (previously masked by the idempotency failures fixed in #24033): mangled `css-tree` lost its `find` export and `@asamuzakjp/dom-selector` failed with `SyntaxError: The requested module 'css-tree' does not provide an export named 'find'` ([failing run](https://github.com/oxc-project/monitor-oxc/actions/runs/28562614557/job/84683456673)). The same export shape appears in commander, csso, colorette, ansis and `@actions/io`, so those were broken too.

## Example

```js
import syntax from "./syntax/index.js";
export const { tokenize, parse, find } = syntax;
```

Before:

```js
import e from "./syntax/index.js";
export const { tokenize: t, parse: n, find: s } = e; // exports `t`, `n`, `s`
```

After:

```js
import e from "./syntax/index.js";
export const { tokenize, parse, find } = e;
```

Verified end-to-end by mangling every file in `[email protected]` and exercising `import { find, parse, generate, walk } from "css-tree"` in node.
camc314 pushed a commit that referenced this pull request Jul 3, 2026
…ed (#24041)

Adds `MangleOptions::reserved` — equivalent to terser / uglify-js / swc `mangle.reserved`: names in the set are never used as mangled names, and bindings that already carry them keep them. Default empty; default output is byte-identical to main (minsize snapshot unchanged).

## Motivation

Node's cjs-module-lexer detects a CommonJS module's named exports by **lexically** scanning for `exports.<name> =` / `module.exports` token patterns — no scope analysis ([its README documents renamed identifiers as "DETECTS: NO EXPORTS"](https://github.com/nodejs/cjs-module-lexer)). UMD / CommonJS wrappers bind `exports` / `module` as ordinary function parameters, and the mangler renames them, erasing every named export the lexer can see.

Surfaced by the monitor-oxc mangler runtime test ([failing run](https://github.com/oxc-project/monitor-oxc/actions/runs/28569108563/job/84702922472), previously masked by #24033 / #24036): `archiver` does `import { queue } from "async"`, and `async`'s dist is a UMD bundle — mangled, the factory parameter `exports` became `e` and node fails with `Named export 'queue' not found`. With `reserved: ["exports", "module"]` the output imports correctly (verified end-to-end in node, including running a queue task).

## Why an opt-in list instead of always keeping these names

Renaming them is ecosystem-standard. Verified empirically — minifying the same UMD sample and importing it in node:

| minifier | renames `exports` param? | `import { queue }` from its output | escape hatch |
| --- | --- | --- | --- |
| terser 5.48 | yes | fails | `mangle.reserved` (verified working) |
| uglify-js 3.19 | yes | fails | `reserved` (verified working) |
| esbuild 0.28 `--minify` | yes | fails | none for identifier mangling |
| swc | yes | fails | terser-style `mangle.reserved` ([swc#3424](swc-project/swc#3424)) |

An earlier revision of this PR kept `exports` / `module` unconditionally; the Minification Size check showed the real cost: ~1% minified on UMD-heavy files (d3: +3.3 kB from ~590 `exports` references, flipping it to *larger than esbuild*), because the point is keeping the literal 7-char token at every export site. No other minifier pays this by default — and rolldown bundles bind `exports` / `module` in every CJS interop wrapper, where node's lexer never looks. So oxc gets the same escape hatch as terser/swc, with the same name.

`MangleOptions` loses `Copy` (it now holds the set); construction sites switch to `..MangleOptions::default()` / `clone()`. Exposed in `oxc-minify` NAPI options (`mangle.reserved: string[]`) and the mangler example (`--reserve-exports`).

monitor-oxc will pass `["exports", "module"]` for its mangler runtime test (its corpus imports prebuilt CJS/UMD dists directly).

For reference, esbuild solves this for its *own* node-platform CJS bundles differently — a dead-code annotation `0 && (module.exports = { a, b })` that cjs-module-lexer recognizes ([esbuild#960](evanw/esbuild#960), [cjs-module-lexer#44](nodejs/cjs-module-lexer#44)); verified that pattern also works appended to fully-mangled output. That could be a future zero-size-cost alternative at the minifier level.
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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