[Bug]: http-client-csharp relies on NPM hoisting behavior

[ascott18]

Describe the bug

Installing packages with pnpm v11 with enableGlobalVirtualStore: true results in the following issues due to undeclared dependencies in Typespec's package.json files:

@typespec/http-client-csharp has undeclared dependency on @azure-tools/typespec-azure-core

$ pnpm --dir typespec exec tsp compile .
TypeSpec compiler v1.12.0

× Compiling
Diagnostics were reported during compilation:

error js-error: Failed to load D:/.pnpm-store/v11/links/@typespec/http-client-csharp/1.0.0-alpha.20260521.5/aac8d44bffe0a214616303272337d1a59a3706494728983f23fcaec0feda23b2/node_modules/@typespec/http-client-csharp/dist/emitter/src/index.js due to the following JS error: Cannot find package '@azure-tools/typespec-azure-core' imported from D:\.pnpm-store\v11\links\@typespec\http-client-csharp\1.0.0-alpha.20260521.5\aac8d44bffe0a214616303272337d1a59a3706494728983f23fcaec0feda23b2\node_modules\@typespec\http-client-csharp\dist\emitter\src\type\operation-final-state-via.js
Did you mean to import "@azure-tools/typespec-azure-core/dist/src/index.js"?

Found 1 error.

@azure-tools/typespec-azure-core has undeclared dependency on @typespec/versioning

$ pnpm --dir typespec exec tsp compile .
TypeSpec compiler v1.12.0

× Compiling
Diagnostics were reported during compilation:

error js-error: Failed to load D:/.pnpm-store/v11/links/@typespec/http-client-csharp/1.0.0-alpha.20260518.6/9fa168bf69d3ecf1dc8bd5eb38e6c7c9be586b3e1d1c239f299a9bdba77df5cd/node_modules/@typespec/http-client-csharp/dist/emitter/src/index.js due to the following JS error: Cannot find package '@typespec/versioning' imported from D:\.pnpm-store\v11\links\@azure-tools\typespec-azure-core\0.68.0\bab52293e26dd81b1928d49e8e2dcb9748ba2fa13ac81adaa31dfa2c4bb7ca5b\node_modules\@azure-tools\typespec-azure-core\dist\src\decorators\preview-version.js
Did you mean to import "@typespec/versioning/dist/src/index.js"?

Found 1 error.

Workaround, via pnpm-workspace.yaml:

packageExtensions:
  "@typespec/http-client-csharp":
    dependencies:
      "@azure-tools/typespec-azure-core": "*"
  "@azure-tools/typespec-azure-core":
    dependencies:
      "@typespec/versioning": "*"

Reproduction

package.json:

{
  "name": "backend-api",
  "version": "0.1.0",
  "type": "module",
  "private": true,
  "dependencies": {
    "@typespec/compiler": "latest",
    "@typespec/http": "latest",
    "@typespec/openapi3": "latest",
    "@typespec/http-client-csharp": "latest"
  }
}

pnpm-workspace.yaml:

enableGlobalVirtualStore: true

Then,

pnpm i
pnpm exec tsp compile .

Checklist

• Follow our Code of Conduct
• Check that there isn't already an issue that request the same bug to avoid creating a duplicate.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion.
• The provided reproduction is a minimal reproducible example of the bug.

[github-actions]

🎯 Issue Triage

The http-client-csharp package has an undeclared runtime dependency on typespec-azure-core, and typespec-azure-core has an undeclared dependency on typespec/versioning. These missing declarations cause failures when using pnpm v11 with enableGlobalVirtualStore: true, which enforces strict dependency isolation.

Category: Bug
Area: emitter:client:csharp

⚠️ No TypeScript reproduction provided — the issue is in package.json dependency declarations, not TypeSpec source code. The package.json + pnpm-workspace.yaml repro in the issue is sufficient to reproduce.

🔍 Analysis

• http-client-csharp's package.json is missing typespec-azure-core as a declared dependency (relying on hoisting in standard npm/pnpm layouts).
• typespec-azure-core's package.json is missing typespec/versioning as a declared dependency.
• With pnpm's enableGlobalVirtualStore: true (pnpm v11), packages only have access to their explicitly declared dependencies — hoisting is not available as a fallback.
• The workaround (packageExtensions in pnpm-workspace.yaml) confirms the root cause is missing dependencies entries.
• Fix should be to add the missing entries to each package's dependencies or peerDependencies.

📝 Suggested next steps

• Add typespec-azure-core to the declared dependencies or peerDependencies in http-client-csharp's package.json
• Coordinate with the typespec-azure-core maintainers to add typespec/versioning to that package's declared dependencies
• Verify the fix works with pnpm enableGlobalVirtualStore: true

Generated by Agentic Triage

[JoshLove-msft]

@ascott18 the csharp emitter is built using npm rather than pnpm. Do you hit the same issue using npm?

[ascott18]

No, because npm hoists all packages, its able to find the undeclared runtime dependencies "by accident" by their virtue of being included as dependencies of other packages. But pnpm (and yarn) don't hoist all dependencies - they need to be properly declared in the package.json of the package which depends upon them.