OAS 3.0<>Swagger 2.0 Mismatch with FormData Binary Payloads

[nielsbox]

Description

When using Swagger 2.0 we can define our binary payloads like this:

       - description: The file payload
          format: document
          in: formData
          name: payload
          required: true
          type: file

Meaning the file would get validated as a file and if you used jsonschema's draft4_format_checker extensions, you would get a File-Like object as input.

def add_checks():
    """Extend connexion's default validation with additional checks
    """

    def check_payload(payload):
        """Check whether the uploaded document is supported."""
        check = validate_mimetype(payload)
        payload.seek(0)
        return check

    draft4_format_checker.checks('binary')(check_payload)

Now using the OAS 3.0 spec, we define formdata payloads this way:

requestBody:
          content:
            multipart/form-data:
              schema:
                type: object
                properties:
                  payload:
                    description: The file payload
                    format: binary
                    type: string
                required: 
                  - payload

Meaning that when validating the request the file is expected to be a string. As a hack, we now replace the File-Like objects with empty strings. This code only gets executed if the consumed mimetype (that we now need to define by the OAS 3.0 spec) is in the FORM_CONTENT_TYPES list. https://github.com/spec-first/connexion/blob/main/connexion/decorators/validation.py#L173

Because of this line and the changed spec our extended validation doesn't work anymore as it just validates an empty string. This creates a mismatch between OAS 3.0 and Swagger 2.0 functionality.

Expected behaviour

The File-Like or bytestring object gets prompted during validation.

Actual behaviour

Empty string gets validated.

Steps to reproduce

See above code scripts.

Additional info:

Output of the commands:

• python --version
• Python 3.8
• pip show connexion | grep "^Version\:"
• 2.13.0