[Bug]: http-client-js emits unused private contexts for empty clients

[yoskeoka]

Describe the bug

@typespec/http-client-js emits private context fields for generated clients that have no operations. Those fields are initialized but never read. A consumer that enables TypeScript noUnusedLocals cannot compile the generated client because TypeScript reports TS6133 for each field.

This is specific to the JavaScript client emitter. It is related to, but distinct from, #8479, which is scoped to the C# client emitter.

Reproduction

The following public TypeSpec project reproduces the issue:

https://github.com/yoskeoka/ai-arena/tree/f41393621ba220d01a1841e523e11b34c573c938/typespec

From the repository root:

pnpm --dir typespec install
pnpm --dir typespec run build
pnpm --dir operator-ui install --frozen-lockfile
pnpm --dir operator-ui run build

The TypeSpec service emits empty AiArenaClient and SharedClient classes. The generated
operator-ui/src/generated/operator-api/src/aiArenaClient.ts contains equivalent output to:

export class AiArenaClient {
  #context: AiArenaClientContext;

  constructor(endpoint: string, options?: AiArenaClientOptions) {
    this.#context = createAiArenaClientContext(endpoint, options);
    // ... subclients
  }
}

export class SharedClient {
  #context: SharedClientContext;

  constructor(endpoint: string, options?: SharedClientOptions) {
    this.#context = createSharedClientContext(endpoint, options);
  }
}

Neither #context field is read. The final command fails with:

src/generated/operator-api/src/aiArenaClient.ts(...): error TS6133: '#context' is declared but its value is never read.

The service TypeSpec source and generated-client configuration are at the linked revision. The
consumer enables noUnusedLocals in operator-ui/tsconfig.app.json.

Versions

The issue reproduces with the current npm stable release line tested on 2026-09-16:

• @typespec/compiler, @typespec/http, @typespec/openapi3: 1.16.0
• @typespec/rest: 0.86.0
• @typespec/http-client-js: 0.16.2
• generated runtime: @typespec/ts-http-runtime: 0.3.9

It also reproduces with the project's previous pins (1.13.0 / 0.83.0 / 0.15.0 / 0.2.1).

Expected behavior

The JS emitter should generate strict-TypeScript-safe output for clients with no operations.
For example, it could omit the unused context state and imports, omit empty clients where that is
compatible with the generated API, or otherwise reference the created context. Consumers should
not need to weaken noUnusedLocals or permanently hand-edit generated artifacts.

[github-actions]

🎯 Issue Triage
@typespec/http-client-js emits initialized private context fields for clients with no operations, but generated code never reads those fields.
Projects enabling TypeScript noUnusedLocals therefore fail compilation with TS6133.
Category: Bug
Area: emitter:client:js

⚠️ No reproduction provided. A minimal repro would help diagnose this issue.

🔍 Analysis

The linked external project provides an end-to-end reproduction, but no minimal TypeSpec snippet or playground link. Empty client generation appears to declare and initialize #context unconditionally even though only operations consume it. Searches for the TS6133, empty-client, and unused-context signatures found no matching JS emitter issue. #8479 is C#-specific, and #5388 concerned suppressing empty MGC clients rather than strict TypeScript compatibility.

📝 Suggested next steps

• Reduce the linked project to a minimal inline TypeSpec case.
• Add a JS emitter regression test for an empty client with noUnusedLocals.
• Emit context state only when the generated client consumes it, while preserving required subclient initialization.

Generated by Agentic Triage