feat(nestjs): support file upload in DTO with @format binary JSDoc tag

[hyeonss0417]

Summary

Add support for file upload fields in DTOs using the @format binary JSDoc tag for NestJS integration.

Problem

Previously, file uploads were only recognized when using the @UploadedFile() decorator. When a DTO class contained a MulterFile type property, TJS would convert the entire MulterFile interface into a schema, causing buffer, stream, and other internal properties to appear in the Swagger UI.

Solution

Use the @format binary JSDoc tag to explicitly indicate file upload fields in DTOs.

Usage

export class CreateFoodIntakeFromImageDto {
  /**
   * Food image file
   * @format binary
   */
  file!: any;

  /**
   * Intake time (defaults to current time if not provided)
   * @format date-time
   * @example "2024-11-24T12:30:00.000Z"
   */
  intakeAt?: string;
}

Generated OpenAPI Schema

requestBody:
  required: true
  content:
    multipart/form-data:
      schema:
        type: object
        properties:
          file:
            type: string
            format: binary
            description: Food image file
          intakeAt:
            type: string
            format: date-time
        required:
          - file

Changes

• schemaBuilder.ts: Detect @format binary tag in mergeJsDocAnnotations and convert to { type: 'string', format: 'binary' } schema
• openapiGenerator.ts: Automatically use multipart/form-data content type when Body DTO contains @format binary properties
• tests: Add tests for file upload scenarios with @format binary

Why @format binary instead of type detection?

We chose @format binary JSDoc tag over hardcoding type names (MulterFile, Express.Multer.File, etc.):

• Follows OpenAPI standard
• Explicit and clear intent
• Flexible and not dependent on specific type names

[github-actions]

LGTM 👍