fix(es/minifier): Handle `undefined` args by cuyl · Pull Request #11573 · swc-project/swc

cuyl · 2026-02-21T16:47:57Z

Evaluate when parameters is empty or undefined.

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crates/swc_ecma_minifier/src/compress/pure/evaluate.rs

github-actions · 2026-02-21T16:57:01Z

Binary Sizes

File	Size
`swc.linux-x64-gnu.node`	28M (28587208 bytes)

Commit: 1ccae49

codspeed-hq · 2026-02-21T17:05:35Z

Merging this PR will not alter performance

✅ 184 untouched benchmarks

_{Comparing cuyl:handle-undefined-args (29f8cb9) with main (de2a348)}

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crates/swc_ecma_minifier/src/compress/pure/evaluate.rs

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crates/swc_ecma_minifier/src/compress/pure/evaluate.rs

cuyl · 2026-02-22T02:06:18Z

Preserve trailing-argument exceptions in undefined fast path

This toPrecision(undefined) fast path folds the call even when additional arguments are present, but the precheck only filters may_have_side_effects and misses some expressions that throw without side effects. For example, (1.23).toPrecision(undefined, 1n + 1) must throw a TypeError while evaluating the second argument, yet this branch rewrites the whole call to a string literal and suppresses that runtime error. This regression is introduced by the new undefined-argument folding condition.

Useful? React with 👍 / 👎.

These edge cases are exist issue.
We have to refactor fn may_have_side_effects to handle more edge cases.
But I found 100+ use cases in other files.
It may have too much impact, maybe we can do it in another PR.
@kdy1

kdy1 · 2026-02-22T06:19:08Z

You can do it in another PR, but it should be merged before this PR

cuyl · 2026-02-22T07:38:31Z

I'll do it when I have time.

Closes swc-project#11572

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crates/swc_ecma_minifier/src/compress/pure/evaluate.rs

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crates/swc_ecma_minifier/src/compress/pure/evaluate.rs

crates/swc_ecma_utils/src/lib.rs

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crates/swc_ecma_utils/src/lib.rs

socket-security · 2026-02-23T11:40:58Z

No dependency changes detected. Learn more about Socket for GitHub.

👍 No dependency changes detected in pull request

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crates/swc_ecma_utils/src/lib.rs

cuyl · 2026-02-23T13:56:20Z

@codex review

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crates/swc_ecma_minifier/src/compress/pure/evaluate.rs

cuyl · 2026-02-23T15:27:13Z

@codex review

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crates/swc_ecma_utils/src/lib.rs

cuyl · 2026-02-23T16:38:29Z

@codex review

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crates/swc_ecma_utils/src/lib.rs

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crates/swc_ecma_minifier/src/compress/pure/evaluate.rs

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crates/swc_ecma_utils/src/lib.rs

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crates/swc_ecma_minifier/src/compress/pure/evaluate.rs

cuyl · 2026-02-24T07:00:55Z

This PR’s scope has expanded significantly beyond the original issue. I’ve realized that fully addressing may_have_side_effects is an endless task without a full runtime. So I’ve reverted those specific changes. I have kept the new test cases to document the behavior for future work.

Since this is a pre-existing issue not introduced by this PR, I don't think it blocks this PR.

@kdy1

cuyl · 2026-02-24T07:25:00Z

We have a wrong ouput on 1.23.toExponential(undefined), I believe fixing this regression is also a high priority issue.

cuyl · 2026-02-24T07:25:32Z

@codex review

kdy1 · 2026-02-24T07:30:43Z

Can we fix the correctness issue of toPrecision first, with another PR?

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cuyl · 2026-02-24T08:30:00Z

Ok, I will close this PR and open another.
@kdy1

cuyl requested a review from a team as a code owner February 21, 2026 16:47

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cuyl force-pushed the handle-undefined-args branch from bb2ce82 to 343441c Compare February 21, 2026 17:25

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cuyl requested a review from kdy1 February 22, 2026 02:08

kdy1 marked this pull request as draft February 23, 2026 03:13

cuyl force-pushed the handle-undefined-args branch from 2ef47dc to b7b7ee3 Compare February 23, 2026 06:57

cuyl added 3 commits February 23, 2026 15:26

fix(es/minifier): Handle undefined args

95d9760

Closes swc-project#11572

fix(es/minifier): Preserve spread

f28bf97

fix(es/minifier): Fix edge cases

0230bf6

cuyl force-pushed the handle-undefined-args branch from b7b7ee3 to 0230bf6 Compare February 23, 2026 07:27

cuyl marked this pull request as ready for review February 23, 2026 07:27

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cuyl marked this pull request as draft February 23, 2026 08:37

cuyl force-pushed the handle-undefined-args branch from e31f3d4 to 2ce465e Compare February 23, 2026 10:03

chore: add tests

b05433d

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cuyl requested a review from a team as a code owner February 23, 2026 11:40

Handles unary plus with BigInt for side effects detection

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Simplifies control flow for early return in argument handling

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Improves BigInt negative exponent handling in side effect checks

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Extends bigint detection to handle binary expressions

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Fix some edge cases for BigInt-valued operators

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exponential operation may have side effects

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refactor

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cuyl force-pushed the handle-undefined-args branch 2 times, most recently from 2b265de to b9bacc8 Compare February 24, 2026 06:30

Revert all changes of may_have_side_effects and keep test cases

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cuyl closed this Feb 24, 2026

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