fix: ignore module federation source maps to prevent build warnings

[intagliated]

Description

This PR resolves an issue where building extensions produces verbose source map parsing warnings from upstream packages (specifically @module-federation/error-codes).

While these builds complete successfully, missing TypeScript source files in third-party modules trigger ENOENT: no such file or directory errors from source-map-loader, which clutters the build logs.

By adding an exclude rule targeting /node_modules\/@module-federation/ inside src/extensionConfig.ts, the builder now defensively skips parsing these known broken/missing upstream source maps.

Related Issues

Fixes #111

Type of Change

• Bug fix (non-breaking change which fixes an issue)

[Darshan808]

Thanks for working on this @intagliated
Do you really see those logs?
Can you share your output, or even better write a test proving they exist currently.

What I see: #111 (comment)

[Darshan808]

Thanks for digging. Yes if the fix is already in the upstream and warning logs are no longer seen here, than we can close this PR.

[intagliated]

Hi @Darshan808.
The original warning from the issue:

WARNING in ./node_modules/@module-federation/error-codes/dist/index.cjs.js
    ⚠ Module Warning (from source-map-loader):
    │ Failed to parse source map from '.../node_modules/@module-federation/error-codes/src/error-codes.ts'
    │ Error: ENOENT: no such file or directory

The dependency chain that caused it:

@jupyterlab/builder@4.6.0-alpha.0   ← the early test release of the builder (Dec 2025)
  → @rspack/core@1.6.4              ← the bundler it depended on at that time (version 1.6.4)
    → @module-federation/runtime-tools@0.21.4
      → @module-federation/runtime@0.21.4
        → @module-federation/error-codes@0.21.4  ← the package that caused the warning

These are all version numbers — the number after @ identifies the exact release of a package. 0.21.4 is an older release of @module-federation/error-codes, while 2.5.1 is the current stable release pulled in today. The jump from 0.x to 2.x indicates a major rewrite happened between these releases.

Why @module-federation/error-codes@0.21.4 caused the warning:
Its source map file (dist/index.cjs.js.map) pointed to source files that were never included in the published package:

"sources": [
    "../src/error-codes.ts",
    "../src/getShortErrorMsg.ts",
    "../src/desc.ts"
]

So source-map-loader tried to find these .ts files, couldn't, and printed the ENOENT warning.

Why @module-federation/error-codes@2.5.1 no longer causes the warning:
The newer release now embeds the source content directly inside the map file via sourcesContent — so the build tool no longer needs to look up any external files on disk. Nothing goes missing, no warning.

Tests added:
I've also added regression tests in tests/test_extension_config.py that verify:

1. The @module-federation exclude rule exists in src/extensionConfig.ts
2. The rule survived TypeScript compilation in lib/extensionConfig.js
3. The exclude rule is placed directly alongside the source-map-loader rule, not just mentioned elsewhere in the file

[intagliated]

Sure.

[intagliated]

Hi, I want to reopen the pull request again to understand why the CI failed -16/21

[Darshan808]

I added a extension build job in a PR and here' the CI https://github.com/jupyterlab/jupyter-builder/actions/runs/28006945873/job/82890989868?pr=126
There's no any warnings as mentioned in #111. I believe we should close this PR as well as the issue.

[intagliated]

ok