feat(openapi3): Add @list decorator when x-ms-list extension is true

[Copilot]

OpenAPI specs using x-ms-list: true to mark list operations weren't generating the corresponding @list decorator in TypeSpec output.

Changes

• Modified getExtensions() in decorators.ts to detect x-ms-list: true and emit both @list and @extension("x-ms-list", true) decorators
• Added test suite covering true/false/absent scenarios for the extension

Example

Input OpenAPI:

paths:
  /widgets:
    get:
      x-ms-list: true
      operationId: Widgets_list
      responses:
        '200':
          content:
            application/json:
              schema:
                type: array
                items:
                  $ref: '#/components/schemas/Widget'

Generated TypeSpec (before):

@extension("x-ms-list", true)
@route("/widgets")
@get
op Widgets_list(): Widget[];

Generated TypeSpec (after):

@list
@extension("x-ms-list", true)
@route("/widgets")
@get
op Widgets_list(): Widget[];

The @list decorator marks the operation as paginated, while the @extension preserves roundtrip compatibility.

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Original prompt

---

This section details on the original issue you should resolve

<issue_title>Add support for adding list decorator to operations when detecting the corresponding extension</issue_title>
<issue_description>### Clear and concise description of the problem

Related https://github.com/microsoft/openai-openapi-pr/issues/568

Based on the following OpenAPI description, we should get the following TypeSpec definition imported

openapi: 3.0.0
info:
  title: Widget Service
  version: 0.0.0
tags:
  - name: Widgets
paths:
  /widgets:
    get:
      # this is the extension that matters
      x-ms-list: true
      operationId: Widgets_list
      description: List widgets
      parameters: []
      responses:
        '200':
          description: The request has succeeded.
          content:
            application/json:
              schema:
                type: array
                items:
                  $ref: '#/components/schemas/Widget'
        default:
          description: An unexpected error response.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Error'
      tags:
        - Widgets
    post:
      operationId: Widgets_create
      description: Create a widget
      parameters: []
      responses:
        '200':
          description: The request has succeeded.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Widget'
        default:
          description: An unexpected error response.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Error'
      tags:
        - Widgets
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/Widget'
  /widgets/{id}:
    get:
      operationId: Widgets_read
      description: Read widgets
      parameters:
        - name: id
          in: path
          required: true
          schema:
            type: string
            readOnly: true
      responses:
        '200':
          description: The request has succeeded.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Widget'
        default:
          description: An unexpected error response.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Error'
      tags:
        - Widgets
    patch:
      operationId: Widgets_update
      description: Update a widget
      parameters:
        - name: id
          in: path
          required: true
          schema:
            type: string
            readOnly: true
      responses:
        '200':
          description: The request has succeeded.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Widget'
        default:
          description: An unexpected error response.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Error'
      tags:
        - Widgets
      requestBody:
        required: true
        content:
          application/merge-patch+json:
            schema:
              $ref: '#/components/schemas/WidgetMergePatchUpdate'
    delete:
      operationId: Widgets_delete
      description: Delete a widget
      parameters:
        - name: id
          in: path
          required: true
          schema:
            type: string
            readOnly: true
      responses:
        '204':
          description: 'There is no content to send for this request, but the headers may be useful. '
        default:
          description: An unexpected error response.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Error'
      tags:
        - Widgets
  /widgets/{id}/analyze:
    post:
      operationId: Widgets_analyze
      description: Analyze a widget
      parameters:
        - name: id
          in: path
          required: true
          schema:
            type: string
            readOnly: true
      responses:
        '200':
          description: The request has succeeded.
          content:
            text/plain:
              schema:
                type: string
        default:
          description: An unexpected error response.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Error'
      tags:
        - Widgets
components:
  schemas:
    Error:
      type: object
      required:
        - code
        - message
      properties:
        code:
          type: integer
          format: int32
        message:
          type: string
    Widget:
      type: object
      required:
        - id
        - weight
        - color
      properties:
        id:
          type: string
      ...

</details>



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- Fixes microsoft/typespec#9608

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commit: 5e6c6f1

[github-actions]

All changed packages have been documented.

• ✅ @typespec/openapi3

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@typespec/openapi3 - feature ✏️

importer - Add support for x-ms-list extension to add @list decorator to operations

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