Exposed entries with the same file base name result in duplicated assets in manifest

[dalafik]

Describe the bug

Reproduces on

"@module-federation/rsbuild-plugin": "2.8.0"

If plugin config exposes entry points with the same base name, but different extensions, like these:

exposes: {
  '.': './src/index.tsx',
  './css': './src/index.css',
}

then resulting mf-manifest.json will contain duplicated entries in exposes/assets fields:

"exposes": [
  {
    "id": "App:.",
    "name": ".",
    "assets": {
      "js": {
        "sync": [
          "static/js/async/__federation_expose_default_export.js",
          "static/js/async/__federation_expose_css.js"
        ],
        "async": []
      },
      "css": {
        "sync": [
          "static/css/async/__federation_expose_default_export.css",
          "static/css/async/__federation_expose_css.css"
        ],
        "async": []
      }
    },
    "path": "."
  },
  {
    "id": "App:css",
    "name": "css",
    "assets": {
      "js": {
        "sync": [
          "static/js/async/__federation_expose_default_export.js",
          "static/js/async/__federation_expose_css.js"
        ],
        "async": []
      },
      "css": {
        "sync": [
          "static/css/async/__federation_expose_default_export.css",
          "static/css/async/__federation_expose_css.css"
        ],
        "async": []
      }
    },
    "path": "./css"
  }

Here is AI report of the investigation (if it helps):

This is a bug in @module-federation/manifest v2.8.0, not intentional
behavior.

The plugin uses getFileNameWithOutExt() — which strips the file extension — as
a map key when grouping expose chunks to expose entries:

// @module-federation/manifest/dist/utils.js
function getFileNameWithOutExt(str) {
    return str.replace(path.extname(str), '');
}

When both expose inputs share the same filename stem:

"packages/design-system/src/index.ts"  → key: "packages/design-system/src/index"
"packages/design-system/src/index.css" → key: "packages/design-system/src/index"
//                                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
//                                              COLLISION — same key, different files

The collision chain:

Step	Location	What happens
_getModuleAssets() assigns chunk assets to a bucket map	StatsManager.js:167–220	Both input paths reduce to the same stem key → assets from both chunks are merged into one bucket
fileExposeKeyMap groups expose names by file stem	ContainerManager.js:116–128	Both "." and "./css" map to the same key → Set([".", "./css"])
Final stats generation iterates fileExposeKeyMap	StatsManager.js:410–443	For every expose name in the set, pushes the same merged asset list
mf-stats.json "file" field is also wrong	ModuleHandler.js:386	The ./css expose overwrites the . expose in exposesMap (same stem key)

The strategy was designed for the case documented in the plugin source:
multiple expose aliases pointing to the same file (e.g.
"." → Button.jsx, "./backup" → Button.jsx). It breaks when two
different files happen to share the same stem (index.ts and index.css).

Reproduction

https://github.com/dalafik/module-federation-bug.git

Used Package Manager

npm

System Info

System:
    OS: Linux 6.11 Ubuntu 24.04.2 LTS 24.04.2 LTS (Noble Numbat)
    CPU: (20) x64 13th Gen Intel(R) Core(TM) i7-13700H
    Memory: 18.82 GB / 30.87 GB
    Container: Yes
    Shell: 5.2.21 - /bin/bash
  Binaries:
    Node: 22.17.1
    Yarn: 1.22.22
    npm: 10.9.2
    pnpm: 9.15.4
    bun: 1.3.13
  Browsers:
    Chrome: 148.0.7778.167
    Firefox: 152.0.5
    Firefox Developer Edition: 152.0.5

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.