77 lines
2.6 KiB
Markdown
77 lines
2.6 KiB
Markdown
# Rolldown minifier drops `while(` keyword — invalid syntax in Safari
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**Status:** To be filed
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**Workaround applied:** `build: { minify: "esbuild" }` in `vite.config.mts`
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## Summary
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Rolldown's minifier drops the `while(`/`for(;` keyword when a `while (x in globalThis)` loop is bundled alongside other module-level variable declarations. The resulting output is a syntax error that crashes Safari.
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## Target repositories
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- https://github.com/rolldown/rolldown/issues
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- https://github.com/oxc-project/oxc/issues (underlying minifier)
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## Environment
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| Package | Version |
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|---|---|
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| `vite` | 8.0.1 |
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| `rolldown` | 1.0.0-rc.10 |
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| `@oxc-project/types` | 0.120.0 |
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| Triggered by | `@ark/schema` 0.56.0 / `arktype` 2.1.29 |
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## Source
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File: `node_modules/@ark/schema/out/shared/registry.js`
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```js
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let _registryName = "$ark";
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let suffix = 2;
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while (_registryName in globalThis)
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_registryName = `$ark${suffix++}`;
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export const registryName = _registryName;
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```
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## Actual minified output
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```js
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un=Pe(`implementedTraits`),dn=`$ark`,fn=2;dn in globalThis;)dn=`$ark${fn++}`;var pn=dn;
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```
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The `while(` keyword is missing. The orphaned `)` is a syntax error.
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## Expected output
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```js
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var dn=`$ark`,fn=2;for(;dn in globalThis;)dn=`$ark${fn++}`;var pn=dn;
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```
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## Impact
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Safari throws: `SyntaxError: Unexpected keyword 'in'. Expected a ';' following a return statement.`
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Chrome and Firefox appear to tolerate the malformed output.
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## Reproduction attempts
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Direct Rolldown calls (even with the full `arktype` + `@better-fetch/fetch` bundle) do **not** reproduce the bug. It only manifests through Vite's full production build pipeline. This strongly suggests the issue is in the interaction between **Vite's module preprocessing** (dependency pre-bundling, plugin transforms, scope-flattening of ESM modules) and Rolldown's minifier `sequences` optimization pass.
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Hypothesis: Vite's pipeline produces a flattened scope where multiple `var` declarations from different original modules are consecutive. When the `sequences` optimizer then tries to fold those `var` declarations into the `for` loop init, it incorrectly drops the `for(var ` prefix when the loop condition contains the `in` operator.
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## Notes
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- Related closed issue: [rolldown/rolldown#8146](https://github.com/rolldown/rolldown/issues/8146) — "Minifier incorrectly merges statements into for-in expression via comma operator"
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- To reproduce: run `pnpm build` in this project **without** `build.minify: "esbuild"` — the broken chunk is `getAuthor-*.js`
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## Workaround
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Add to `vite.config.mts`:
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```ts
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build: {
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minify: "esbuild",
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},
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```
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esbuild correctly outputs `for(;Dt in globalThis;)Dt=\`$ark${za++}\``.
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