Support OpenAPI V3 YAML/JSON oneof about goa HOT 4 CLOSED

I'd love to find a better way of encoding unions in a way that works across various encoders that is compatible with clients generated from the OpenAPI specification!

As mentioned in the linked issue the current implementation adds a Type field as the union discriminator and the value itself is serialized as a JSON string in the Value field. The client code that a oneof OpenAPI spec would generate would not be compatible with what the current implementation does. So it's not just a matter of updating the generated spec but it's mostly about how Goa handles union types in HTTP. We'd need to come up with a scheme that makes it possible for server and client Go methods to understand the underlying type so responses and/or requests can be unmarshaled correctly.

from goa.

So it's not just a matter of updating the generated spec but it's mostly about how Goa handles union types in HTTP.

Isn't this actually exactly what's required? It seems that all that's missing is the enumeration of the acceptable types for the serialised value - the response is JSON anyway, what is stopping the generated spec from including the type references?

anyOf:
      - $ref: '#/components/schemas/Dog'
      - $ref: '#/components/schemas/Cat'

from goa.

Not quite, the spec above would describe a response like:

{ "pet1": { "bark": true }, "pet2": { "claws": 20 } }

where Goa generates:

{ "pet1": { "Type": "dog", "Value": "{\"bark\":true}" }, "pet2": { "Type": "cat", "Value": "{\"claws\":20}" } }

Also to make the problem clearer the spec above would also work for:

<data><pet1><bark>true</bark></pet1><pet2><claws>20</claws></pet2></data>

where Goa generates:

<data><pet1><Type>dog</Type><Value>{"bark":true}</Value></pet1><pet2><Type>cat</Type><Value>{"claws":20}</Value></pet2></data>

from goa.

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from goa.