[BUG] [typescript-nestjs-server] Header parameters generated without @Headers() decorator; values never bound

[Prakash-86]

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Issue title: [BUG][typescript-nestjs-server] Header parameters generated without @Headers() decorator; values never bound at runtime

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Description

The typescript-nestjs-server generator does not emit NestJS @Headers() decorators for OpenAPI parameters with in: header. The generated controller has plain method parameters (e.g. xRequestId: string, xIdempotencyKey: string) with no decorator. In NestJS, only parameters with a decorator (@Body(), @Param(), @Query(), @Headers(), etc.) are bound from the request. As a result, header parameter values are always undefined at runtime even when the client sends the headers.

The generator's documentation lists "Header" as a supported parameter feature (OAS2/OAS3), but the generated code does not fulfill this for NestJS.

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openapi-generator version

• Version used: 7.17.0 (via @openapitools/openapi-generator-cli 2.28.x)
• Regression: Unknown; not tested on earlier versions.

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OpenAPI declaration file content or url

openapi: 3.0.0
info:
  title: Example API
  version: 1.0.0
paths:
  /items:
    post:
      operationId: createItem
      parameters:
        - name: x-request-id
          in: header
          required: false
          schema:
            type: string
        - name: x-idempotency-key
          in: header
          required: false
          schema:
            type: string
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
      responses:
        '201':
          description: Created

---

Generation Details

CLI command:

npx @openapitools/openapi-generator-cli generate \
  -i openapi.yaml \
  -g typescript-nestjs-server \
  -o ./out \
  --additional-properties=useSingleRequestParameter=true,importFileExtension=.js,supportsES6=true

• Generator: typescript-nestjs-server
• Options: useSingleRequestParameter=true (and commonly used .js/supportsES6 for Node)

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Steps to reproduce

1. Save the YAML above as openapi.yaml.
2. Run the generation command above.
3. Open out/controllers/Default.controller.ts (or the generated controller for the operation).
4. Observe that the createItem method has parameters xRequestId: string and xIdempotencyKey: string with no @Headers('...') decorator.

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What's the actual output vs expected output?

Actual (excerpt): Header parameters are plain arguments; Nest does not bind them.

createItem(
  @Body() body: object,
  xRequestId: string,
  xIdempotencyKey: string,
  @Req() request: Request
): SomeResponse | Promise<SomeResponse> | Observable<SomeResponse> {
  return this.api.createItem({ body, xRequestId, xIdempotencyKey }, request);
}

Expected (excerpt): Header parameters should have @Headers() so Nest binds values from the request.

createItem(
  @Body() body: object,
  @Headers('x-request-id') xRequestId: string,
  @Headers('x-idempotency-key') xIdempotencyKey: string,
  @Req() request: Request
): SomeResponse | Promise<SomeResponse> | Observable<SomeResponse> {
  return this.api.createItem({ body, xRequestId, xIdempotencyKey }, request);
}

The controller should also import Headers from @nestjs/common.

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Related issues/PRs

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Suggest a fix

The generator's NestJS controller template (likely under modules/openapi-generator/src/main/resources/typescript-nestjs-server/) should emit @Headers('{{paramName}}') (or the appropriate mustache variable for the header name) for parameters where param.isHeader or equivalent is true, and include Headers in the @nestjs/common import. This would align the generated code with Nest's parameter binding and the documented Header parameter support.

[aryobenholzner]

should be fixed by #22960