fix: preserve default-scope shared cache aliases

[dmchoi77]

Close #858
Follow-up to #861

Summary

This adds a shared cache compatibility layer for default share-scope modules.

#861 fixes the dev optimizeDeps gate for shared singleton React, but the repro in #858 can still fail when generated runtime code looks for the same shared module under different cache keys. Newer scoped cache keys use values such as default:react, while default-scope compatibility paths can still observe the older unscoped shape, such as react.

This patch centralizes that behavior with a canonical shared cache descriptor plus default-scope aliases.

Problem

Shared dependency configuration and runtime shared cache storage are separate layers.

For example:

shared: {
  react: { singleton: true, import: false },
}

At runtime, generated loadShare wrappers and remoteEntry code store resolved shared modules in globalThis.__mf_module_cache__.share.

The same default-scope shared module may be addressed as:

default:react  # canonical scoped key
react          # default-scope compatibility alias

If one generated path writes default:react while another path reads react, the remote can miss the host-provided singleton and fall back to its own React instance. That can still produce duplicate React symptoms even after React is excluded from dev pre-bundling.

Changes

• Added getSharedCacheDescriptor() in src/utils/packageUtils.ts.

  • canonical is the scoped cache key, for example default:react.
  • aliases contains default-scope compatibility keys, for example react.
  • Custom share scopes do not get default-scope aliases, preserving scope isolation.

• Added generated runtime helpers:

  • __mfGetSharedCacheDescriptor
  • __mfReadSharedCache
  • __mfWriteSharedCache

• Updated generated loadShare modules to read and write through the shared cache helpers.

• Updated generated remoteEntry and host auto-init code to use the same helpers for:

  • external shared provider bridging,
  • singleton cache aliasing,
  • direct shared cache seeding,
  • import: false shared provider seeding,
  • host auto-init shared preloading.

• Updated the react/compiler-runtime pre-build path to resolve React through the same compatible shared cache read.

Tests

• Added src/utils/__tests__/packageUtils.test.ts coverage for:

  • default-scope canonical keys and aliases,
  • custom scope isolation,
  • alias read promotion to the canonical key,
  • writes to canonical and default-scope alias keys.

• Updated virtual module tests to assert shared cache helper usage in generated loadShare, remoteEntry, and host auto-init code.

• Updated integration coverage to verify generated shared chunks use the compatibility helpers and default-scope descriptors.

Verification

pnpm exec tsc -p tsconfig.json --noEmit
pnpm exec vitest run --dir src
pnpm exec vitest run integration
git diff --check

Results:

• TypeScript check passed.
• Source tests passed: 34 files / 569 tests.
• Integration tests passed: 9 files / 34 tests.
• Diff whitespace check passed.

pnpm exec vitest run --dir src still prints the existing MaxListenersExceededWarning, but all tests pass.

Compatibility Notes

This intentionally keeps default-scope compatibility while preserving custom-scope isolation.

New generated code reads the canonical key first. If only a default-scope alias exists, the helper promotes that value to the canonical key. Writes always store the canonical key and also fill empty alias slots for default-scope compatibility.

This should allow version-skewed host and remote builds to share the same singleton module while avoiding cross-scope collisions.

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@module-federation/vite@862

commit: df18257

[gioboa]

@abhayzmp is this pre-release working for you?

[abhayzmp]

I work in IST hours and I'm packed up for the day. But feel free to just clone the repro and follow readme.md to test the changes. Once I login tomorrow I can test and revert

[gioboa]

@dmchoi77 I tested the @abhayzmp 's repo an the issue is not solved.

[gioboa]

Tests With Different Frameworks

[gioboa]

I tested the repo with the issue and now it's working.
Thanks @dmchoi77 for your help 👏