[Feature Request] Missing support for unions

[jnv]

Given a union structure in profile like this:

[ string! | number! ]

I recieve this exception on one-service start:

.../node_modules/@superfaceai/one-service/dist/schema.types.js:235
            throw new Error(`Variable type not implemented for: ${structure.kind}`);
                  ^

Error: Variable type not implemented for: UnionStructure
    at outputType (.../node_modules/@superfaceai/one-service/dist/schema.types.js:235:19)
    at outputType (.../node_modules/@superfaceai/one-service/dist/schema.types.js:231:46)
    at .../node_modules/@superfaceai/one-service/dist/schema.types.js:219:27
    at Array.forEach (<anonymous>)
    at outputType (.../node_modules/@superfaceai/one-service/dist/schema.types.js:217:89)
    at outputType (.../node_modules/@superfaceai/one-service/dist/schema.types.js:231:46)
    at generateStructureResultType (.../node_modules/@superfaceai/one-service/dist/schema.types.js:102:18)
    at generateUseCaseFieldConfig (.../node_modules/@superfaceai/one-service/dist/schema.types.js:60:24)
    at generateProfileTypes (.../node_modules/@superfaceai/one-service/dist/schema.types.js:28:36)
    at generate (.../node_modules/@superfaceai/one-service/dist/schema.js:41:91)

Profile example

usecase GetRoomsAvailability {
  input {
    arrivalDate! string!
    departureDate! string!

    "Room/apartment IDs"
    rooms! [string! | number!]
  }

  result [
    {
      date! string!
      availableQuantity! number!
      rooms! [string! | number!]
    }
  ]
}

[freaz]

After some dive to unions in GraphQL, I don't see a way how to support them. Because GraphQL doesn't allow unions in input at all and for outputs it must be an object.

So only unions defined in Comlink as below would work.

model WeatherInformation {
  airTemperature
  atmosphericPressure
}

model WeatherDetailedInformation {
  airTemperature
  atmosphericPressure
  wind
  windGusts
  rain
}

model WeatherData WeatherInformation | WeatherDetailedInformation

Since the limitation in GraphQL is big, I wouldn't implement it. Also because the union in profile can be rewritten to single type.

Action item here is to document it in README as known limitation.

• Specification
• GitHub Issue

---

There is new specification and suggested as an alternative for unions for inputs. It is called OneOf Input Objects. Once implementation is merged, we should be able to use it to map Comlink Profile Unionsas OneOf Input Objects.