feat(minifier): fold boolean-literal ternary branches in value contexts by Dunqing · Pull Request #24110 · oxc-project/oxc

Dunqing · 2026-07-03T09:08:03Z

What

Fold a ternary with one boolean literal branch into && / ||, in value positions (call arguments, returns, assignments).

Input	Output	Condition
`c ? false : x`	`!c && x`	always safe
`c ? x : true`	`!c \|\| x`	always safe
`c ? true : x`	`c \|\| x`	only when `c` is a boolean
`c ? x : false`	`c && x`	only when `c` is a boolean

We already do this inside if tests. This PR does it everywhere else. The first two rows produce the exact same value for any c. The last two rows would return c itself instead of true/false, so they need a boolean-typed c.

How

New match arms in minimize_conditional_expression, next to the existing a ? true : false => !!a block. The dropped branch must be side-effect free (same check the existing block uses). The fold is skipped when it would make the output longer, e.g. a || b ? false : c would need !(a || b), so it stays as is. Equality tests invert for free: a === b ? false : x => a !== b && x.

Example

// input
use(foo() ? false : bar());
use(a === b ? false : compute());

// before
use(foo()?!1:bar()),use(a===b?!1:compute());

// after
use(!foo()&&bar()),use(a!==b&&compute());

Found by re-minifying oxc's minsize output with terser -c: typescript.js alone has ~290 of these. All minsize fixtures stay equal or smaller.

Implemented with Claude Code, reviewed and verified by me.

codspeed-hq · 2026-07-03T09:12:12Z

Merging this PR will not alter performance

✅ 52 untouched benchmarks
⏩ 19 skipped benchmarks¹

_{Comparing minifier-ternary-bool-fold (cf589f0) with main (bf1a151)}

19 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 · 2026-07-03T09:20:27Z

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Dunqing · 2026-07-06T07:38:51Z

@codex review

chatgpt-codex-connector · 2026-07-06T07:46:08Z

Codex Review: Didn't find any major issues. Chef's kiss.

Reviewed commit: cf589f0b06

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oxc-guard · 2026-07-06T08:01:47Z

Monitor Oxc

Commit: cf589f0b062d

suite	result
Test262	✅
Build	✅
Isolated Declarations	✅
(transformer)	✅
(formatter_dcr)	✅
(dce)	✅
(compressor)	✅
(formatter)	❌
(whitespace)	✅
(mangler)	❌
(codegen)	✅

Dunqing · 2026-07-06T08:25:37Z

Merge activity

Jul 6, 8:25 AM UTC: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
Jul 6, 8:25 AM UTC: Dunqing added this pull request to the Graphite merge queue.
Jul 6, 8:30 AM UTC: Merged by the Graphite merge queue.

…ts (#24110) ## What Fold a ternary with one boolean literal branch into `&&` / `||`, in value positions (call arguments, returns, assignments). | Input | Output | Condition | |---|---|---| | `c ? false : x` | `!c && x` | always safe | | `c ? x : true` | `!c \|\| x` | always safe | | `c ? true : x` | `c \|\| x` | only when `c` is a boolean | | `c ? x : false` | `c && x` | only when `c` is a boolean | We already do this inside `if` tests. This PR does it everywhere else. The first two rows produce the exact same value for any `c`. The last two rows would return `c` itself instead of `true`/`false`, so they need a boolean-typed `c`. ## How New match arms in `minimize_conditional_expression`, next to the existing `a ? true : false` => `!!a` block. The dropped branch must be side-effect free (same check the existing block uses). The fold is skipped when it would make the output longer, e.g. `a || b ? false : c` would need `!(a || b)`, so it stays as is. Equality tests invert for free: `a === b ? false : x` => `a !== b && x`. ## Example ```js // input use(foo() ? false : bar()); use(a === b ? false : compute()); ``` ```js // before use(foo()?!1:bar()),use(a===b?!1:compute()); // after use(!foo()&&bar()),use(a!==b&&compute()); ``` Found by re-minifying oxc's minsize output with `terser -c`: typescript.js alone has ~290 of these. All minsize fixtures stay equal or smaller. Implemented with Claude Code, reviewed and verified by me.

### 🚀 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]>

github-actions Bot added the A-minifier Area - Minifier label Jul 3, 2026

Dunqing force-pushed the minifier-ternary-bool-fold branch from 3260236 to cf589f0 Compare July 6, 2026 07:36

Dunqing added the run-monitor-oxc Add to a PR to dispatch oxc-project/monitor-oxc CI against it label Jul 6, 2026

Dunqing marked this pull request as ready for review July 6, 2026 08:01

Dunqing requested a review from overlookmotel as a code owner July 6, 2026 08:01

oxc-guard Bot removed the run-monitor-oxc Add to a PR to dispatch oxc-project/monitor-oxc CI against it label Jul 6, 2026

Dunqing added the 0-merge Merge with Graphite Merge Queue label Jul 6, 2026

graphite-app Bot force-pushed the minifier-ternary-bool-fold branch from cf589f0 to 2d9b0b3 Compare July 6, 2026 08:26

graphite-app Bot merged commit 2d9b0b3 into main Jul 6, 2026
29 checks passed

graphite-app Bot removed the 0-merge Merge with Graphite Merge Queue label Jul 6, 2026

graphite-app Bot deleted the minifier-ternary-bool-fold branch July 6, 2026 08:30

oxc-guard Bot mentioned this pull request Jul 6, 2026

release(crates): oxc v0.139.0 #24218

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feat(minifier): fold boolean-literal ternary branches in value contexts#24110

feat(minifier): fold boolean-literal ternary branches in value contexts#24110
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