How to generate nullable struct references?

[benjamin-ratier]

Hello,

I want to be able to make a struct nullable:

type Bar struct {
   Foo *FooStruct `json:"foo"`
}

I’m using kin-openapi, to validate my http calls against my generated OpenAPI file, and for a struct to be optional in my http response, I need:

...
  - foo:
    - nullable: true 
    - allOf:
      - $ref: '#components/schemas/foostruct'
...

I was able to move the generated $ref into allOf with reflector.DefaultOptions and InterceptNullability (or InterceptProperty), but I don't see how to set nullable in the jsonschema.Schema object and propagate it in openapi3.schema object.

Would you have any suggestions ?

Thanks a lot in advance !

[vearutop]

I think jsonschema.InterceptNullability would be suitable for this, please check an example.

https://go.dev/play/p/Dt5HxQ8XJUp

	jr.DefaultOptions = append(jr.DefaultOptions, jsonschema.InterceptNullability(func(params jsonschema.InterceptNullabilityParams) {
		if params.RefDef != nil && params.Type.Kind() == reflect.Ptr {
			params.Schema.WithAllOf(jsonschema.Null.ToSchemaOrBool(), params.OrigSchema.ToSchemaOrBool())
			params.Schema.Ref = nil
		}
	}))

components:
  schemas:
    Bar:
      properties:
        foo:
          allOf:
          - nullable: true
          - $ref: '#/components/schemas/FooStruct'
          type: object
      type: object

or

	jr.DefaultOptions = append(jr.DefaultOptions, jsonschema.InterceptNullability(func(params jsonschema.InterceptNullabilityParams) {
		if params.RefDef != nil && params.Type.Kind() == reflect.Ptr {
			params.Schema.AddType(jsonschema.Null)
			params.Schema.WithAllOf(params.OrigSchema.ToSchemaOrBool())
			params.Schema.Ref = nil
		}
	}))

components:
  schemas:
    Bar:
      properties:
        foo:
          allOf:
          - $ref: '#/components/schemas/FooStruct'
          nullable: true
          type: object
      type: object
    FooStruct:

Alternatively, you can put nullability under the refrence, but this would also affect the cases when field is a value, not a pointer (might be undesirable).

https://go.dev/play/p/_J09FYf8uRF

	jr.DefaultOptions = append(jr.DefaultOptions, jsonschema.InterceptNullability(func(params jsonschema.InterceptNullabilityParams) {
		if params.Type.Kind() == reflect.Ptr {
			params.Schema.AddType(jsonschema.Null)
		}
	}))

components:
  schemas:
    Bar:
      properties:
        foo:
          $ref: '#/components/schemas/FooStruct'
      type: object
    FooStruct:
      nullable: true
      properties:
        baz:
          type: string
      type: object

[benjamin-ratier]

Perfect !

params.Schema.AddType(jsonschema.Null) did exactly what I wanted.

Thanks a lot :)