Generage code for upload file is wrong

Swagger-codegen version

3.0.36

Description

I have a api as follow:

  /v1/mch-mgr/merchants/{merchantId}/products/{productId}/head:

If i write detail info with the api in the same file, it is work success

  /v1/mch-mgr/merchants/{merchantId}/products/{productId}/head:
    post:
      operationId: updateHead
      tags:
        - MchMgrProduct
      requestBody:
        content:
          multipart/form-data:
            schema:
              type: object
              properties:
                file:
                  type: string
                  format: binary

      security:
        - BearerAuth: [ ]
      responses:
        200:
          description: "success"

Tthe generate code is right:

   @Override
    public ResponseEntity<Void> updateHead(MultipartFile file) {
        return MchMgrProductApi.super.updateHead(file);
    }

If i write detail info with the api in different files, it is wrong:

/v1/mch-mgr/merchants/{merchantId}/products/{productId}/head:
    $ref: ./resources/mch-mgr/product/product-head.yaml
    

product-head.yaml file:

    post:
          operationId: updateHead
          tags:
            - MchMgrProduct
          requestBody:
            content:
              multipart/form-data:
                schema:
                  type: object
                  properties:
                    file:
                      type: string
                      format: binary

          security:
            - BearerAuth: [ ]
          responses:
            200:
              description: "success"

Tthe generate code is wrong:

    @Override
    public ResponseEntity<Void> updateHead(String file) {
        return MchMgrProductApi.super.updateHead(file);
    }

Start by reproducing the difference in Swagger-codegen 3.0.36 between the inline endpoint and the external product-head.yaml reference. Trace Java generation for the multipart/form-data file property and compare the generated updateHead signatures. Done means both definitions generate MultipartFile rather than String.