feat(minifier): replace `const` with `let` for non-exported read-only variables by sapphi-red · Pull Request #8733 · oxc-project/oxc

sapphi-red · 2025-01-26T10:49:36Z

Replace const with let when that value does not have any assignments and not exposed.

sapphi-red · 2025-01-26T10:49:58Z

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Boshen · 2025-01-26T10:55:19Z

esbuild does const replacements, I'd like to do that at some point too.

So this should go to late pass instead of pre pass?

sapphi-red · 2025-01-26T10:59:36Z

esbuild does const replacements, I'd like to do that at some point too.

So this should go to late pass instead of pre pass?

I first implemented in the late pass and it wasn't idempotent because collapse_variable_declarations can merge const a = 1; let b = 2; into let a = 1, b = 2.
The information that it was a const can be obtained from SymbolFlags::ConstVariable. Would that work for const replacements?

codspeed-hq · 2025-01-26T11:02:47Z

CodSpeed Performance Report

Merging #8733 will not alter performance

_{Comparing 01-26-feat_minifier_replace_const_with_let_for_non-exported_read-only_variables (e0117db) with main (dc0b0f2)}

Summary

✅ 33 untouched benchmarks

Boshen · 2025-01-26T12:35:22Z

esbuild does const replacements, I'd like to do that at some point too.
So this should go to late pass instead of pre pass?

I first implemented in the late pass and it wasn't idempotent because collapse_variable_declarations can merge const a = 1; let b = 2; into let a = 1, b = 2. The information that it was a const can be obtained from SymbolFlags::ConstVariable. Would that work for const replacements?

Yes, we can merge this PR regardless.

Boshen · 2025-01-26T12:35:32Z

Merge activity

Jan 26, 7:35 AM EST: The merge label '0-merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
Jan 26, 7:35 AM EST: A user added this pull request to the Graphite merge queue.
Jan 26, 7:51 AM EST: A user merged this pull request with the Graphite merge queue.

… variables (#8733) Replace `const` with `let` when that value does not have any assignments and not exposed.

## [0.48.1] - 2025-01-26 ### Features - b7f13e6 ast: Implement utf8 to utf16 span converter (#8687) (Boshen) - 6589c3b mangler: Reuse variable names (#8562) (翠 / green) - 29bd215 minifier: Minimize `Infinity.toString(radix)` to `'Infinity'` (#8732) (Boshen) - e0117db minifier: Replace `const` with `let` for non-exported read-only variables (#8733) (sapphi-red) - 9e32f55 minifier: Evaluate `Math.sqrt` and `Math.cbrt` (#8731) (sapphi-red) - 360d49e minifier: Replace `Math.pow` with `**` (#8730) (sapphi-red) - 2e9a560 minifier: `NaN.toString(radix)` is always `NaN` (#8727) (Boshen) - cbe0e82 minifier: Minimize `foo(...[])` -> `foo()` (#8726) (Boshen) - e9fb5fe minifier: Dce pure expressions such as `new Map()` (#8725) (Boshen) ### Bug Fixes - 0944758 codegen: Remove parens from `new (import(''), function() {})` (#8707) (Boshen) - 33de70a mangler: Handle cases where a var is declared in a block scope (#8706) (翠 / green) - d982cdb minifier: `Unknown.fromCharCode` should not be treated as `String.fromCharCode` (#8709) (sapphi-red) - e7ab96c transformer/jsx: Incorrect `isStaticChildren` argument for `Fragment` with multiple children (#8713) (Dunqing) - 3e509e1 transformer/typescript: Enum merging when same name declared in outer scope (#8691) (branchseer) ### Performance - dc0b0f2 manger: Remove useless `tmp_bindings` (#8735) (Dunqing) - e472ced mangler: Optimize handling of collecting lived scope ids (#8724) (Dunqing) - 8587965 minifier: Normalize `undefined` to `void 0` before everything else (#8699) (Boshen) ### Refactor - 58002e2 ecmascript: Remove the lifetime annotation on `MayHaveSideEffects` (#8717) (Boshen) - 10e5920 linter: Move finishing default diagnostic message to `GraphicalReporter` (#8683) (Sysix) - 52a37d0 mangler: Simplify initialization of `slots` (#8734) (Dunqing) - 6bc906c minifier: Allow mutating arguments in methods called from `try_fold_known_string_methods` (#8729) (sapphi-red) - bf8be23 minifier: Use `Ctx` (#8716) (Boshen) - 0af0267 minifier: Side effect detection needs symbols resolution (#8715) (Boshen) - 32e0e47 minifier: Clean up `Normalize` (#8700) (Boshen) - c792068 semantic: Simplify `ScopeTree::iter_bindings` (#8723) (Dunqing) ### Testing - 03229c5 minifier: Fix broken tests (#8722) (Boshen) Co-authored-by: Boshen <1430279+Boshen@users.noreply.github.com>

github-actions bot added A-minifier Area - Minifier A-ast Area - AST C-enhancement Category - New feature or request labels Jan 26, 2025

This was referenced Jan 26, 2025

refactor(minifier): allow mutating arguments in methods called from try_fold_known_string_methods #8729

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feat(minifier): replace Math.pow with ** #8730

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sapphi-red mentioned this pull request Jan 26, 2025

feat(minifier): evaluate Math.sqrt and Math.cbrt #8731

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sapphi-red marked this pull request as ready for review January 26, 2025 10:50

sapphi-red marked this pull request as draft January 26, 2025 10:51

sapphi-red force-pushed the 01-26-feat_minifier_evaluate_math.sqrt_and_math.cbrt_ branch from 9556f95 to 3378661 Compare January 26, 2025 11:08

sapphi-red force-pushed the 01-26-feat_minifier_replace_const_with_let_for_non-exported_read-only_variables branch from e554c5c to 655a300 Compare January 26, 2025 11:08

sapphi-red force-pushed the 01-26-feat_minifier_evaluate_math.sqrt_and_math.cbrt_ branch from 3378661 to 899d108 Compare January 26, 2025 11:12

sapphi-red force-pushed the 01-26-feat_minifier_replace_const_with_let_for_non-exported_read-only_variables branch from 655a300 to a40e368 Compare January 26, 2025 11:12

Boshen force-pushed the 01-26-feat_minifier_evaluate_math.sqrt_and_math.cbrt_ branch from 899d108 to 2f3b1d4 Compare January 26, 2025 11:18

Boshen force-pushed the 01-26-feat_minifier_replace_const_with_let_for_non-exported_read-only_variables branch from a40e368 to f8f8355 Compare January 26, 2025 11:18

sapphi-red force-pushed the 01-26-feat_minifier_evaluate_math.sqrt_and_math.cbrt_ branch from 2f3b1d4 to ad8ec4a Compare January 26, 2025 11:21

sapphi-red force-pushed the 01-26-feat_minifier_replace_const_with_let_for_non-exported_read-only_variables branch from f8f8355 to 4ff54aa Compare January 26, 2025 11:21

sapphi-red marked this pull request as ready for review January 26, 2025 11:24

sapphi-red force-pushed the 01-26-feat_minifier_evaluate_math.sqrt_and_math.cbrt_ branch from ad8ec4a to dda3b76 Compare January 26, 2025 12:08

sapphi-red force-pushed the 01-26-feat_minifier_replace_const_with_let_for_non-exported_read-only_variables branch from 4ff54aa to 413c513 Compare January 26, 2025 12:08

sapphi-red changed the base branch from 01-26-feat_minifier_evaluate_math.sqrt_and_math.cbrt_ to graphite-base/8733 January 26, 2025 12:14

sapphi-red force-pushed the graphite-base/8733 branch from dda3b76 to 9e32f55 Compare January 26, 2025 12:19

sapphi-red force-pushed the 01-26-feat_minifier_replace_const_with_let_for_non-exported_read-only_variables branch from 413c513 to 2a1f336 Compare January 26, 2025 12:19

sapphi-red changed the base branch from graphite-base/8733 to main January 26, 2025 12:20

sapphi-red force-pushed the 01-26-feat_minifier_replace_const_with_let_for_non-exported_read-only_variables branch from 2a1f336 to cf091dd Compare January 26, 2025 12:20

Boshen added the 0-merge Merge with Graphite Merge Queue label Jan 26, 2025

feat(minifier): replace const with let for non-exported read-only…

e0117db

… variables (#8733) Replace `const` with `let` when that value does not have any assignments and not exposed.

Boshen force-pushed the 01-26-feat_minifier_replace_const_with_let_for_non-exported_read-only_variables branch from cf091dd to e0117db Compare January 26, 2025 12:44

graphite-app bot merged commit e0117db into main Jan 26, 2025
25 checks passed

graphite-app bot deleted the 01-26-feat_minifier_replace_const_with_let_for_non-exported_read-only_variables branch January 26, 2025 12:51

oxc-bot mentioned this pull request Jan 26, 2025

release(crates): v0.48.1 #8738

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feat(minifier): replace `const` with `let` for non-exported read-only variables#8733

feat(minifier): replace `const` with `let` for non-exported read-only variables#8733
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01-26-feat_minifier_replace_const_with_let_for_non-exported_read-only_variables

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