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fix(javascript): keep new and Array() on a built-in the program assigns in the minifier - #22761
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…ssigns in the minifier
Dropping `new` from a built-in, writing `Array()` or `Object()` as a literal and reading Babel's rest loop as `[...arguments]` checked only that the name is undeclared, so `Error = function () {}` before `new Error()` changed what it built. Read them as built-ins only where the program never assigns the name, through a pattern or loop head included.
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Priority: ➖ Normal Change: Bug fix Merge Risk: 🟡 Moderate · up to
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Review comments at @lib/javascript/syntax-printer.js:
- Line 24355: Update optimizeNew and the original-call optimization path to
apply the assigned-built-in guard before any unsafe rewrite, including
converting `new` expressions to calls or `Array(...)` and `Object()` calls to
literals; preserve the existing rewrites when the built-in is not assigned.
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📒 Files selected for processing: 5
.changeset/070-minify-assigned-built-in.mdlib/javascript/syntax-printer.jstest/helpers/swcSmaller.jstest/specCases/minify-corpora.spectest.jstest/unitCases/syntax-printer.unittest.js
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- test/specCases/minify-corpora.spectest.js
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This PR is packaged and the instant preview is available (10f2d19). Install it locally:
npm i -D webpack@https://pkg.pr.new/webpack@10f2d19
yarn add -D webpack@https://pkg.pr.new/webpack@10f2d19
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This PR contains the following updates: | Package | Change | [Age](https://docs.renovatebot.com/merge-confidence/) | [Confidence](https://docs.renovatebot.com/merge-confidence/) | |---|---|---|---| | [webpack](https://github.com/webpack/webpack) | [`5.112.0` → `5.112.2`](https://renovatebot.com/diffs/npm/webpack/5.112.0/5.112.2) |  |  | --- >⚠️ **Warning** > > Some dependencies could not be looked up. Check the [Dependency Dashboard](issues/99) for more information. --- ### Release Notes <details> <summary>webpack/webpack (webpack)</summary> ### [`v5.112.2`](https://github.com/webpack/webpack/blob/HEAD/CHANGELOG.md#51122) [Compare Source](webpack/webpack@v5.112.1...v5.112.2) ##### Patch Changes - Reduce repeated scans when concatenating imported modules. (by [@​xiaoxiaojx](https://github.com/xiaoxiaojx) in [#​22865](webpack/webpack#22865)) - Avoid allocating CSS module sets for single-group chunks. (by [@​xiaoxiaojx](https://github.com/xiaoxiaojx) in [#​22866](webpack/webpack#22866)) - Return the value of every module type loaded with `importModule()`. (by [@​alexander-akait](https://github.com/alexander-akait) in [#​22869](webpack/webpack#22869)) ### [`v5.112.1`](https://github.com/webpack/webpack/blob/HEAD/CHANGELOG.md#51121) [Compare Source](webpack/webpack@v5.112.0...v5.112.1) ##### Patch Changes - Rebuild a lazy barrel in watch when what it defers changes, and keep the imports and re-exports it still runs. (by [@​aryanraj45](https://github.com/aryanraj45) in [#​22699](webpack/webpack#22699)) - Rebuild under `cacheUnaffected` a module whose re-export target goes or returns. (by [@​aryanraj45](https://github.com/aryanraj45) in [#​22749](webpack/webpack#22749)) - Fix "Self-reference dependency has unused export name" for CommonJS namespace re-exports. (by [@​alexander-akait](https://github.com/alexander-akait) in [#​22791](webpack/webpack#22791)) - Fix `exportType: "style"` CSS modules throwing outside the runtime chunk. (by [@​lazerg](https://github.com/lazerg) in [#​22833](webpack/webpack#22833)) - Fix crash when a CSS module with `exportType: "style"` imports an ignored stylesheet. (by [@​codeXsidd](https://github.com/codeXsidd) in [#​22846](webpack/webpack#22846)) - Keep empty process environment variables that `.env` files don't define in `DotenvPlugin`. (by [@​alexander-akait](https://github.com/alexander-akait) in [#​22794](webpack/webpack#22794)) - Rehash an ESM entry chunk when a chunk it imports by file name changes. (by [@​alexander-akait](https://github.com/alexander-akait) in [#​22804](webpack/webpack#22804)) - Handle a NUL inside an HTML CDATA section the way the parsing spec does. (by [@​dependabot](https://github.com/apps/dependabot) in [#​22811](webpack/webpack#22811)) - Keep module exports live across chunks, runtimes, HMR and eval, sparing globals. (by [@​alexander-akait](https://github.com/alexander-akait) in [#​22733](webpack/webpack#22733)) - Await asynchronous modules that `ProvidePlugin` injects into ES modules. (by [@​alexander-akait](https://github.com/alexander-akait) in [#​22728](webpack/webpack#22728)) - Keep a resolve that ends after the compiler closed from throwing. (by [@​alexander-akait](https://github.com/alexander-akait) in [#​22795](webpack/webpack#22795)) - Preserve string names passed to SharedWorker constructors. (by [@​bjohansebas](https://github.com/bjohansebas) in [#​22770](webpack/webpack#22770)) - Preserve string contents when extracting source map comments. (by [@​bjohansebas](https://github.com/bjohansebas) in [#​22768](webpack/webpack#22768)) - Scope strict-mode, async and generator block function declarations to their block. (by [@​alexander-akait](https://github.com/alexander-akait) in [#​22800](webpack/webpack#22800)) - Preserve raw dotenv values when reusing cached environment files. (by [@​Eshiv-Pandey](https://github.com/Eshiv-Pandey) in [#​22787](webpack/webpack#22787)) - Preserve assigned or patched built-ins, conversions and pattern targets. (by [@​aryanraj45](https://github.com/aryanraj45) in [#​22761](webpack/webpack#22761)) - Keep globals a `globalThis` write replaces, and `slice` on a patched array. (by [@​alexander-akait](https://github.com/alexander-akait) in [#​22862](webpack/webpack#22862)) - Skip HTML script tags for shared chunks that emit no JavaScript. (by [@​bjohansebas](https://github.com/bjohansebas) in [#​22779](webpack/webpack#22779)) - Keep the digits Firefox lays out a minified CSS percentage with. (by [@​alexander-akait](https://github.com/alexander-akait) in [#​22718](webpack/webpack#22718)) - Reject a second `srcset` descriptor after a `0x` density descriptor. (by [@​alexander-akait](https://github.com/alexander-akait) in [#​22741](webpack/webpack#22741)) - Minify JavaScript faster, folding string methods on constants and `x -= 1`. (by [@​alexander-akait](https://github.com/alexander-akait) in [#​22823](webpack/webpack#22823)) - Shorten minified JavaScript, and keep it running like its source. (by [@​alexander-akait](https://github.com/alexander-akait) in [#​22717](webpack/webpack#22717)) - Drop more unused functions, arguments, calls, global reads and variable copies when minifying JavaScript. (by [@​alexander-akait](https://github.com/alexander-akait) in [#​22789](webpack/webpack#22789)) - Minify JavaScript smaller where swc does, and fold a function's `length` right. (by [@​alexander-akait](https://github.com/alexander-akait) in [#​22826](webpack/webpack#22826)) - Reduce JavaScript output size where oxc or swc produce smaller output. (by [@​alexander-akait](https://github.com/alexander-akait) in [#​22829](webpack/webpack#22829)) - Update watchpack to 2.6.3 and rebuild on a `node_modules` created mid-build. (by [@​alexander-akait](https://github.com/alexander-akait) in [#​22743](webpack/webpack#22743)) - Support `concatenateModules` with `cacheUnaffected`. (by [@​alexander-akait](https://github.com/alexander-akait) in [#​22746](webpack/webpack#22746)) - Update schema-utils to 4.8.1. (by [@​alexander-akait](https://github.com/alexander-akait) in [#​22774](webpack/webpack#22774)) - Keep CSS fallbacks, vendor overrides, `oklch()` hues and HTML elements. (by [@​alexander-akait](https://github.com/alexander-akait) in [#​22753](webpack/webpack#22753)) - Validate `CleanPlugin` and `DotenvPlugin` options with a precompiled check, so valid options no longer compile their schema at startup. (by [@​alexander-akait](https://github.com/alexander-akait) in [#​22758](webpack/webpack#22758)) - Speed up startup and CSS minification, sharing the compile cache with workers. (by [@​xiaoxiaojx](https://github.com/xiaoxiaojx) in [#​22706](webpack/webpack#22706)) - Use precise, generic types for modules, parsers, generators, stats and loaders. (by [@​alexander-akait](https://github.com/alexander-akait) in [#​22731](webpack/webpack#22731)) </details> --- ### Configuration 📅 **Schedule**: (UTC) - Branch creation - "before 9am on tuesday" - Automerge - At any time (no schedule defined) 🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied. ♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox. 🔕 **Ignore**: Close this PR and you won't be reminded about this update again. --- - [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check this box --- This PR has been generated by [Mend Renovate CLI](https://github.com/renovatebot/renovate). <!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiI0NC4xNzUuMSIsInVwZGF0ZWRJblZlciI6IjQ0LjE3NS4xIiwidGFyZ2V0QnJhbmNoIjoiZGV2ZWxvcCIsImxhYmVscyI6WyJkZXBlbmRlbmNpZXMiLCJyZW5vdmF0ZSJdfQ==--> Reviewed-on: https://code.futo.org/harbor/harbor/pulls/2035
Summary
Dropping
newfrom a built-in, writingArray()/Object()as a literal, and reading Babel's rest loop as[...arguments]only checked that the name is undeclared. A program that assigns the built-in got different code. They now usereadsUnassignedGlobal, which also checkspatternWritesnow, so an assignment through destructuring or afor…oftarget counts too.What kind of change does this PR introduce?
fix
Did you add tests for your changes?
Yes, in test/unitCases/syntax-printer.unittest.js: two KEPT_CASES (terser equality) and a test running the sweep above plus Babel's rest loop at ES2020. All fail on main, and each of the four changes reverted alone fails one.
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
I directed Claude Code to find the bug while comparing the minifier's output with oxc and swc, write the fix and the tests, break each change on purpose, and check size and the corpora against main. I reviewed every change myself.
Summary by CodeRabbit
ArrayorObjectare reassigned or shadowed. Constructor calls now retain their intended behavior in these cases.