FR: option to produce MergePatch types readme.com can consume

[blakew]

Per readme.com support, they don't support type: null to clear field values. Instead, they require type: [null, "string"]

This ticket is a feature request to support this compound type in MergePatch where parameters can be cleared.

Example:

interfaces:
  Target:
     ...
     members:
       payload_map:
          required: false
          initializable: true
          mutable: true
          schema:
            type: object
            additionalProperties:
              type: string

Current output:

components:
  schemas:
    ...
    TargetMergePatch:
      type: object
      properties:
        payload_map:
          oneOf:
            - type: object
              additionalProperties:
                type: string
              description: Pass this value to overwrite the existing value.
              title: Overwrite
            - type: "null"       # unsupported by readme.com
              description: "Pass `null` to clear this field's existing value."
              title: Clear
      additionalProperties: false

Desired output:

components:
  schemas:
    ...
    TargetMergePatch:
      type: object
      properties:
        payload_map:
          oneOf:
            - type: object
              additionalProperties:
                type: string
              description: Pass this value to overwrite the existing value.
              title: Overwrite
            - type: [string, "null"]       # required by readme.com
              pattern: ^null$
              description: "Pass `null` to clear this field's existing value."
              title: Clear
      additionalProperties: false

[emk]

Hmm, I think we'll probably need a more concrete example of a readme.com-compatible merge patch type, including one with a $ref property in it. :-(

[emk]

Also, type: [string, "null"] broke a lot of OpenAPI tools about 6 months ago. The array version of type: [..] was extremely poorly supported. SO we'll need to look at compatibility.

[blakew]

ref example:

    Target:
      members:
        limit:
          required: false
          initializable: true
          mutable: true
          schema:
            $interface: "TargetLimit#SameAsInterface"

Current:

    TargetMergePatch:
      type: object
      properties:
        limit:
          oneOf:
            - $ref: "#/components/schemas/TargetLimitMergePatch"
            - type: "null"
              description: "Pass `null` to clear this field's existing value."
              title: Clear

Desired:

    TargetMergePatch:
      type: object
      properties:
        limit:
          oneOf:
            - $ref: "#/components/schemas/TargetLimitMergePatch"
            - type: [string, "null"]
              pattern: ^null$
              description: "Pass `null` to clear this field's existing value."
              title: Clear