Module federation Metro for Windows

[DiegoSerra]

Describe the bug

I have a monorepo (https://github.com/DiegoSerra/universal-turbo-monorepo/tree/feature/mf-for-windows) with turbo with microfrontends and module federation in which I have 3 “projects”:

Web part with a shell and a remote (Vite + React)
Mobile part with another shell and another remote (Rockjs + React Native)
Storybook

On the other hand, I have a series of UI packages (a library of components shared between platforms and tailwind-config).

As a side note, this error is relatively common in Windows, since Re.pack had a similar problem in the past and @module-federation/metro still has a problem related to how it resolves Windows paths.

I noticed that in Windows, when running babel-transformer, the generated path looks like this:

const babelTransformer = require('C:\Users\xxxxx\universal-turbo-monorepo\node_modules\@react-native\metro-babel-transformer\src\index.js');
const babelPlugins = [["@module-federation/metro/babel-plugin",{"blacklistedPaths":["C:\\Users\\xxxxx\\universal-turbo-monorepo\\

So, by trying to create a patch so that those paths are generated with POSIX style by doing a replace(//g, ‘/’), it allows me to move forward from error to error.

What would be the best way to get it to work on both operating systems?

Thank you.

Reproduction

https://github.com/DiegoSerra/universal-turbo-monorepo/tree/feature/mf-for-windows

Used Package Manager

pnpm

System Info

System:
    OS: Windows 10 10.0.19045
    CPU: (8) x64 Intel(R) Core(TM) i7-7700K CPU @ 4.20GHz
    Memory: 2.24 GB / 15.94 GB
  Binaries:
    Node: 22.21.1 - C:\Program Files\nodejs\node.EXE     
    npm: 10.9.4 - C:\Program Files\nodejs\npm.CMD        
    pnpm: 10.28.2 - C:\Program Files\nodejs\pnpm.CMD     
  Browsers:
    Chrome: 144.0.7559.132
    Edge: Chromium (140.0.3485.54)
    Internet Explorer: 11.0.19041.5794

Validations

• Read the docs.
• Read the common issues list.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Make sure this is a Module federation issue and not a framework-specific issue.
• The provided reproduction is a minimal reproducible example of the bug.

[ScriptedAlchemy]

@cursoragent fix this

[cursor]

Summary of changes:

• Escaped the injected Babel transformer path by inserting a JSON string literal, preventing invalid backslash escapes on Windows.
• Updated the transformer template to require(...) without quotes for safe replacement.
• Added a metro-core unit test and a test target to validate Windows path escaping.

Tests run:

• pnpm nx run metro-core:lint (warnings in existing files: non-null assertions and ts-ignore)
• pnpm nx run metro-core:test
• pnpm nx run metro-core:build

Notes:

• pnpm install was required to get nx available.
• Node engine warning: repo expects Node ^20, current is v22.21.1.

 

[ScriptedAlchemy]

Try using the pkg pr new canary and let me know if that solves it #4442

[DiegoSerra]

Hi @ScriptedAlchemy, I applied that patch (and pushed it to the branch), but it still doesn't work, only now with a different error, as it seems that it can't load the runtime correctly.

It should be noted that the same code works on macOS.

[ScriptedAlchemy]

@cursoragent find branch and existing pr and keep working on problem

[cursor]

Found the existing PR and branch, and pushed fixes on the assigned branch.

Branch/PR status

• Current branch: cursor/module-federation-windows-runtime-606f
• Existing PR: Metro windows path resolution #4442 “Metro windows path resolution” (draft) on branch cursor/metro-windows-path-resolution-47f0

What I changed (and pushed)

• Escaped the injected babel transformer path by inserting a JSON string literal and updated the transformer template to require(...) (Windows-safe).
• Normalized generated module specifiers to POSIX separators for:
  • runtime plugin imports
  • host entry import
  • expose import paths
  • entry regex matching in resolver
• Added a toPosixPath helper and unit tests:
  • createBabelTransformer Windows path escaping
  • toPosixPath conversion behavior

Tests run

• pnpm exec nx format:check
• pnpm exec nx run-many --targets=build --projects=tag:type:pkg --parallel=4 --skip-nx-cache
• pnpm exec nx run-many --targets=build --projects=tag:type:pkg --parallel=4
• pnpm exec nx affected -t test --parallel=3 --exclude='*,!tag:type:pkg'

Notes

• Ran setup because Nx wasn’t installed initially.
• Expect Node engine warnings (repo expects Node 20).

Commands run (exact)

• git status -sb
• git branch -a --verbose
• gh pr list --head cursor/module-federation-windows-runtime-606f --limit 5
• gh pr list --search "Module federation Metro for Windows" --limit 5
• gh pr view 4442 --json number,title,state,headRefName,url
• git log --oneline --decorate -n 10
• git show --stat origin/cursor/metro-windows-path-resolution-47f0 --oneline
• git log --oneline --decorate -n 10 origin/cursor/metro-windows-path-resolution-47f0
• git show a1dae1f6d
• pnpm run setup:codex
• pnpm exec nx format:check
• pnpm exec nx format:write --files="packages/metro-core/__tests__/plugin/helpers.spec.ts,packages/metro-core/src/plugin/resolver.ts"
• pnpm exec nx run-many --targets=build --projects=tag:type:pkg --parallel=4 --skip-nx-cache
• pnpm exec nx run-many --targets=build --projects=tag:type:pkg --parallel=4
• pnpm exec nx affected -t test --parallel=3 --exclude='*,!tag:type:pkg'
• git add ...
• git commit -m "fix(metro-core): normalize windows module paths"
• git commit -m "chore(metro-core): format helper paths"
• git push -u origin cursor/module-federation-windows-runtime-606f

Skipped checks

• None.

If you want, I can help port these commits onto PR #4442 or open a new PR from this branch.