[REQ] Infer const type during 3.1 normalization

[jmspiewak]

Is your feature request related to a problem? Please describe.

Some 3.1 schemas represent enumerations as oneOf consts without type. Current normalization doesn't convert such schemas to enums.

Describe the solution you'd like

During normalization, if a schema with const has no type, it should be inferred from the const value.

Example

  # Input (3.1 schema)
  oneOf:
    - const: "foo"
    - const: "bar"

  # Expected normalized output
  type: string
  enum:
    - foo
    - bar

[amorozov]

I'm sorry in advance if my comment doesn't fit the issue purpose, but is such a normalization (const -> enum) correct at all?

OpenAPI-3.1 permits more complex scenarios for oneOf/const, , e.g. like this:

  oneOf:
    - const: "foo"
    - const: "bar"
    - pattern: '^custom:^\S(?:.*\S)?$'

Such a normalization would break things completely. How to deal with it? Is there a more suitable issue for the problem?