[BUG][typescript-fetch] @deprecated JSDoc missing on operation parameters (parameter isDeprecated always false)

[babariviere]

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 and looked for the fix?

Description

typescript-fetch does not emit @deprecated for operation parameters marked deprecated: true in the spec. #11522 / #11523 added @deprecated for operations and model properties, but individual parameters are still undocumented, and when useSingleRequestParameter is enabled the generated XxxRequest parameter interfaces have no JSDoc at all.

Root cause: DefaultCodegen.fromParameter correctly sets CodegenParameter.isDeprecated from the spec, but TypeScriptFetchClientCodegen.ExtendedCodegenParameter's copy constructor copies ~70 fields and omits isDeprecated, resetting it to false. As a result {{#isDeprecated}} is always false for parameters. The operation and model wrappers copy their own isDeprecated, which is why those cases work.

openapi-generator version

master (7.25.0-SNAPSHOT). Present since the Extended* wrappers were introduced in typescript-fetch.

OpenAPI declaration file content to reproduce

openapi: 3.0.3
info: { title: Example API, version: '1.0' }
paths:
  /items:
    get:
      operationId: listItems
      parameters:
        - name: q
          in: query
          description: Free-text search query.
          schema: { type: string }
        - name: legacyId
          in: query
          deprecated: true
          description: Deprecated. Use id instead.
          schema: { type: string }
      responses:
        '200': { description: OK }

Steps to reproduce

java -jar openapi-generator-cli.jar generate -i spec.yaml -g typescript-fetch -o out \
  --additional-properties=useSingleRequestParameter=true

Current output

export interface ListItemsRequest {
    q?: string;
    legacyId?: string;
}

Expected output

export interface ListItemsRequest {
    /**
     * Free-text search query.
     * @type {string}
     * @memberof ListItemsRequest
     */
    q?: string;
    /**
     * Deprecated. Use id instead.
     * @type {string}
     * @memberof ListItemsRequest
     * @deprecated
     */
    legacyId?: string;
}

Related

• [REQ] Add @deprected JSDoc to deprecated parameters, operations in typescript-fetch #11522 (original REQ)
• typescript-fetch: Support deprecated parameters, operations #11523 (added @deprecated for operations and model properties only)

Suggested fix

Copy isDeprecated in the ExtendedCodegenParameter(CodegenParameter) constructor (as the operation and model wrappers already do), and document the request-parameter interfaces in apis.mustache. PR: #24510