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fix(build): disable SWC mangling on the runtime chunk for AMO determinism - #46236
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SWC still flakes Flask runtime identifier assignment under parallel:false. Keeping SWC compress with mangle disabled was identical across 10/10 Ubuntu Docker Flask rebuilds and faster than classic Terser. Co-authored-by: Cursor <cursoragent@cursor.com>
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Sibling option for discussion: #46235 (classic |
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✨ Files requiring CODEOWNER review ✨👨🔧 @MetaMask/extension-platform (1 files, +23 -9)
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Co-authored-by: Cursor <cursoragent@cursor.com>
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Without SWC mangling, readable-stream keeps `new ErrorWrapper`, and the validator matched that as `new Error`, failing MV2 CI. Co-authored-by: Cursor <cursoragent@cursor.com>
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Builds ready [2c607e8]
⚡ Performance Benchmarks (Total: 🟢 17 pass · 🟡 0 warn · 🔴 0 fail)
Bundle size diffs [🚨 Warning! Bundle size has increased!]
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Global mangle:false broke LavaMoat kits (module/module1 mismatches). Keep mangling for app chunks and disable it only on runtime.* for AMO stability. Co-authored-by: Cursor <cursoragent@cursor.com>
…lidation" This reverts commit 2c607e8.
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Builds ready [fc13092]
⚡ Performance Benchmarks (Total: 🟢 14 pass · 🟡 9 warn · 🔴 2 fail)
Bundle size diffs [🚨 Warning! Bundle size has increased!]
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Co-authored-by: Cursor <cursoragent@cursor.com>
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Builds ready [6c4232e]
⚡ Performance Benchmarks (Total: 🟢 12 pass · 🟡 11 warn · 🔴 2 fail)
Bundle size diffs [🚨 Warning! Bundle size has increased!]
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| * rebuild comparisons (mtree) even when the bundles are otherwise equivalent. | ||
| * Disabling parallel minify keeps that step deterministic and has also been a | ||
| * small wall-clock win in local `yarn dist:mv2` timings. | ||
| * SWC mangling can still produce different `runtime.[contenthash].js` output |
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Any idea why this only seems to impact the runtime bundle? If SWC manging is non-deterministic, I would imagine it might impact other bundles too.
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Unfortunately not. Scoping "mangle: false" to runtime is just an empirical attempt to fix the symptom, but I have no proof that SWC mangling is deterministic elsewhere (it's just empirical at this point).
That said, we've discussed during refinement yesterday that the real solution shall rather be to bump @swc/core, see if it fixes nondeterminism, and if not, understand the root cause, and fix @swc/core directly. That's what I'm trying in this other PR, but I'm not there yet.
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Interesting. Well, at least I was able to test that this worked (details in Slack about struggles to reproduce the issue).
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Description
Reason for the change
Firefox AMO rebuilds MetaMask from source and checks that every file matches the published zip (
mtree/ content hashes). That check was failing becauseruntime.[contenthash].jswas not byte-identical across Linux builds: SWC mangling sometimes picks different short names (for examplecvsl) even withparallel: false.Solution
Disable SWC mangling only for the webpack
runtime.*chunk. Keep mangling on for every other chunk.Turning mangling off for the whole bundle broke the extension at runtime (LavaMoat errors such as
Cannot set properties of undefined (setting 'LavaDome')). Scopingmangle: falseto the runtime chunk keeps AMO builds stable without that breakage.Changelog
CHANGELOG entry: null
Related issues
Fixes: INFRA-3920
Manual testing steps
yarn webpack:lavamoat:build:mv2or the usual dist MV2 command).runtime.[contenthash].jshas the same content hash across builds.LavaDomeconsole errors).Pre-merge author checklist
Pre-merge reviewer checklist
Note
Low Risk
Build-time minification only; scoped to the webpack runtime chunk with mangling unchanged elsewhere.
Overview
Fixes Firefox AMO
mtreefailures whereruntime.[contenthash].jsdiffered byte-for-byte across Linux rebuilds because SWC mangling could pick different short names even withparallel: false.getMinimizers()now uses twoTerserPlugin(SWC) passes: one keeps mangling on for all chunks except@lavamoat/snowand the runtime asset (matched byruntimeChunkRe), and a second appliesmangle: falseonly toruntime.*chunks while still minifying them. Other bundles stay mangled so the extension avoids the LavaMoat /LavaDomebreakage seen when mangling was disabled globally.Reviewed by Cursor Bugbot for commit 6c4232e. Bugbot is set up for automated code reviews on this repo. Configure here.