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robhogan
added this pull request to stack #1940
September 17, 2026 11:47
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Summary:
With `includeAsyncPaths`, Metro writes a server-relative URL for each async dependency into the `paths` argument of `__d(...)`, which the client uses to fetch the split bundle. `getDefaultAsyncDependencyPath` builds that URL with `path.relative` and `path.join`, and never converts separators, so on Windows a dependency at `C:\root\src\bar.js` under server root `C:\root` produces:
```
/src\bar.bundle?modulesOnly=true&runModule=false
```
This is a URL, and Metro's own parsing of bundle URLs treats the pathname as posix (`split('/')` in `parseBundleOptionsFromBundleRequestUrl`), so it should be `/src/bar.bundle?...` on every platform. This passes the joined path through `normalizePathSeparatorsToPosix`, already used in the same file for module debug names. No change on posix.
Changelog: [Fix] Fix backslashes in async bundle paths on Windows (`includeAsyncPaths`)
Test Plan:
Removes `js-test.js` from the Windows skip list. Its three async `paths` tests already assert forward-slash URLs from Windows-style inputs.
Before this change, on Windows CI:
```
✕ includes the paths of async dependencies when requested
- "paths":{"1":"/../bar.bundle?param1=true¶m2=1234&modulesOnly=true&runModule=false"}
+ "paths":{"1":"/..\\bar.bundle?param1=true¶m2=1234&modulesOnly=true&runModule=false"}
✕ async bundle paths override modulesOnly and runModule
✕ passes a paths object (not the id array) for async dependencies
```
After, `yarn jest packages/metro/src/DeltaBundler` passes, and Windows CI on this PR is green for `js-test.js`.
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Copilot review overview
🟢 Approval recommended
The focused fix preserves POSIX behavior and is covered by the re-enabled Windows tests.
Review effort: Balanced
Findings: None
What changed in this PR
Normalizes async bundle URLs to POSIX separators on Windows.
Changes:
- Converts generated bundle paths to forward slashes.
- Re-enables serializer tests on Windows.
| File | Description |
|---|---|
scripts/jestFilter.js |
Removes the resolved Windows test exclusion. |
packages/metro/src/DeltaBundler/Serializers/helpers/js.js |
Normalizes async bundle URL separators. |
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Sep 29, 2026
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With
includeAsyncPaths, each__d(...)call carries a server-relative URL per async dependency, which the client uses to fetch the split bundle. On Windows that URL is built with system path separators, so it comes out as/src\bar.bundle?modulesOnly=true&runModule=false. Metro parses bundle URLs as posix paths:metro/packages/metro/src/lib/parseBundleOptionsFromBundleRequestUrl.js
Lines 91 to 100 in 37c767e
This normalises the separators to
/on every platform. No change on posix.Changelog:
Test plan:
Removes
js-test.jsfrom the Windows skip list. Its asyncpathstests assert forward-slash URLs from Windows-style inputs, and failed on Windows CI before this:Windows CI on this PR is green.