For Forms: Enum Contains Default Against Configuration, and Default is Unsubmittable Anyways

[MarioIshac]

Q&A (please complete the following information)

• OS: Ubuntu 20.04.1
• Browser: Firefox, Chrome
• Installation: Tested on editor.swagger.io
• Swagger-UI version: 3.43.0
• Swagger/OpenAPI version: OpenAPI 3.0.3

Content & configuration

openapi: 3.0.3
paths:
  /test:
    post:
      requestBody:
        content:
          multipart/form-data:
            schema: 
              $ref: '#/components/schemas/TestBody'
components:
  schemas:
    TestBody:
      required:
        - test_enum
      type: object
      properties:
        test_enum:
          allOf:
            - $ref: "#/components/schemas/TestEnum"
    TestEnum:
      enum:
        - A
        - B

Plug into editor.swagger.io.

Describe the bug you're encountering

1. Enum contains default even though no default was configured.
2. Leaving default selected leaves request unsubmittable with red visual indicator, must manually select.

To reproduce

1. Expand /test.
2. Press Try it out.
3. Press execute.
4. See red visual indicator.

Expected behavior

Enum should not have default available in first place, but looking past this, the default should be submittable anyways. Instead, manual selection is required. Not sure if these bugs are related or separate.

Screenshots

Additional Context

Same issue as #3706 and #3890, both closed in 2017.

This applies to enums in form bodies, not as parameters (see below comments). So application/x-www-form-urlencoded and multipart/form-data are affected.

[mathis-m]

valid Minimal Reproduction:
https://editor.swagger.io/?url=https://gist.githubusercontent.com/mathis-m/c3c097c16174acad5415affcc22886e1/raw/7cd158e43b1062aeb4c1eea5ffa88af7824cefc0/KCgSSD1Lqe.txt

openapi: 3.0.3
info:
  title: asd
  version: 0.0.1
paths:
  /test:
    post:
      requestBody:
        content:
          multipart/form-data:
            schema: 
              $ref: '#/components/schemas/TestBody'
      responses:
        200:
          description: ok
components:
  schemas:
    TestBody:
      required:
        - test_enum
      type: object
      properties:
        test_enum:
          allOf:
            - $ref: "#/components/schemas/TestEnum"
    TestEnum:
      enum:
        - A
        - B

[mathis-m]

@MarioIshac Could you include multipart/form-data in the issues description and title because I could not reproduce this for parameters.

[MarioIshac]

Thanks for fixing up my example to add the fields I missed, and will change title & description to include multipart/form-data (and also application/x-www-form-urlencoded, was able to reproduce w/ that).