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fix(minify): preserve destructuring assignment targets - #22839
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This PR is packaged and the instant preview of its latest commit is available. Install it locally:
npm i -D webpack@https://pkg.pr.new/webpack@22839
yarn add -D webpack@https://pkg.pr.new/webpack@22839
pnpm add -D webpack@https://pkg.pr.new/webpack@22839 |
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Priority: ⬇️ Low Change: Bug fix Merge Risk: 🟡 Moderate · up to
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Inline comments:
Review comments at @lib/javascript/syntax-printer.js:
- Line 31299: Update the Sub optimization path to check whether the access is a
pattern target before optimizeSub can flatten it via flattenArrayRead; preserve
the original access when it is part of an assignment pattern.
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📒 Files selected for processing: 4
lib/javascript/syntax-printer.jstest/configCases/optimization/minify-assignment-targets/array.jstest/configCases/optimization/minify-assignment-targets/regexp.jstest/configCases/optimization/minify-assignment-targets/webpack.config.js
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Merging this PR will not alter performance1 warning, 1 note
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Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #22839 +/- ##
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- Coverage 96.54% 96.16% -0.39%
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Files 778 778
Lines 139689 139686 -3
Branches 47804 47801 -3
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- Hits 134866 134328 -538
- Misses 4823 5358 +535
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…the minify CI leg - `[[1][0]] = a` keeps its target: the flattened `[1] = a` does not parse (CodeRabbit on #22839) - a `new Set` or a built-in given an array literal stays where the program patches `Array.prototype`, whose iterator may run code (CodeRabbit on #22837) - the corpora and the fuzzer run as two CI legs, the corpora bounded at 90 min: together they took 37 of the 60 min on a fast runner and passed the limit on a slower one Claude-Session: https://claude.ai/code/session_01ViD41i2KdwwGxrDk7yrjeD
…the minify CI leg - `[[1][0]] = a` keeps its target: the flattened `[1] = a` does not parse (CodeRabbit on #22839) - a `new Set` or a built-in given an array literal stays where the program patches `Array.prototype`, whose iterator may run code (CodeRabbit on #22837) - the corpora and the fuzzer run as two CI legs, the corpora bounded at 90 min: together they took 37 of the 60 min on a fast runner and passed the limit on a slower one Claude-Session: https://claude.ai/code/session_01ViD41i2KdwwGxrDk7yrjeD
* fix(minify): preserve observable string conversions * fix(minify): keep pattern targets and patched array iteration; split the minify CI leg - `[[1][0]] = a` keeps its target: the flattened `[1] = a` does not parse (CodeRabbit on #22839) - a `new Set` or a built-in given an array literal stays where the program patches `Array.prototype`, whose iterator may run code (CodeRabbit on #22837) - the corpora and the fuzzer run as two CI legs, the corpora bounded at 90 min: together they took 37 of the 60 min on a fast runner and passed the limit on a slower one Claude-Session: https://claude.ai/code/session_01ViD41i2KdwwGxrDk7yrjeD * fix(minify): address the open CodeRabbit findings on the minify PRs - an optional call folds on a value `fixedValue` gives only where the name is never written again (#22789) - a `case` label reading a `let` its own case declares keeps the switch, which throws in its dead zone (#22754) - improved cases snapshot their output instead of comparing a string (#22829), and the property-write test logs and snapshots what it writes (#22814) Claude-Session: https://claude.ai/code/session_01ViD41i2KdwwGxrDk7yrjeD * fix(minify): keep what a patched Array.prototype runs, and conversions not pure - a spread array literal stays, kept for its effects, and an array literal is no constant to a built-in, a `+` or a template, where the program patches `Array.prototype` - `"a" + x` read for its truthiness keeps `x`'s conversion unless `pure_conversions` - the parser job's checkout keeps no credentials, and the changeset fits 80 characters Claude-Session: https://claude.ai/code/session_01ViD41i2KdwwGxrDk7yrjeD * fix(minify): keep a dot access a pattern writes from folding Claude-Session: https://claude.ai/code/session_01ViD41i2KdwwGxrDk7yrjeD * fix(minify): keep a spread that must run inside an array literal Dropped alone, `...[1]` printed as a statement does not parse. Claude-Session: https://claude.ai/code/session_01ViD41i2KdwwGxrDk7yrjeD * fix(minify): keep array method calls and `new` spreads a patched `Array.prototype` changes Also record `Array["prototype"]` writes as patches. Claude-Session: https://claude.ai/code/session_01ViD41i2KdwwGxrDk7yrjeD * fix(minify): keep calls to a built-in static the program writes `Math.max = f` or `Object.defineProperty(Math, ...)` before `Math.max(1)` no longer folds or drops the call. Claude-Session: https://claude.ai/code/session_01ViD41i2KdwwGxrDk7yrjeD * test(minify): observe the inherited `arguments[1]` getter Claude-Session: https://claude.ai/code/session_01ViD41i2KdwwGxrDk7yrjeD * test(minify): check inherited holes in the printer's unit tests An indexed property on `Array.prototype` or `Object.prototype`, even once deleted, turns off V8's no-elements fast path for the whole process, which slowed every later config case past its timeout (`require/cjs-and-mjs`). Claude-Session: https://claude.ai/code/session_01ViD41i2KdwwGxrDk7yrjeD * test(minify): update the snapshot main's fixed rules fold Claude-Session: https://claude.ai/code/session_01ViD41i2KdwwGxrDk7yrjeD --------- Co-authored-by: alexander-akait <4567934+alexander-akait@users.noreply.github.com>
Summary
Fix two regressions from #22829: folding array elements or
RegExp.sourceinside assignment patterns changes the destination or produces invalid JavaScript. Reuse the existing pattern-target check, including rest and defaulted targets.let value = 1; [...[value][0]] = [2, 3]valuebecomes[2, 3]valuestays1let value = 1; ({ ...[value][0] } = { answer: 2 })valuebecomes an objectvaluestays1({ answer: /a/.source } = { answer: "b" })in strict modeTypeErrorWhat kind of change does this PR introduce?
fix
Did you add tests for your changes?
Yes:
test/configCases/optimization/minify-assignment-targets/covers writes, nested patterns, loops, defaults, computed keys and reads.main.yarn lintpassed.Does this PR introduce a breaking change?
No.
If relevant, what needs to be documented once your changes are merged or what have you already documented?
n/a
Use of AI
Codex reproduced the regressions, implemented the fixes and tests, and ran validation under the contributor's direction.
Summary by CodeRabbit