Graphqlbundle: Interfaces / inheritance not working (Runtime Object type A is not a possible type for B.)

[paoloposo]

| Q | A
| ---------------- | -----
| Bug report? | yes
| Feature request? | no
| BC Break report? | no
| RFC? | no
| Version/Branch | 0.11.0

In my php model, i have an abstract class Acme\\Entity\\User with some fields, say displayName and username. I also have a concrete class Acme\\Entity\\LocalUser which extends User and has additional fields, say firstName and lastName.

I want to represent that same model in GraphQL. Following the type inheritance documentation, I ended up with this schema:

Query:    # root query
  type: object
  config:
    fields:
      user:
        type: User
        args:
          username: String
          self: Boolean
        resolve: '@=resolver(''my_user_resolver'', [args])'

User:
  type: interface
  config:
    fields:
      username:
        type: "String"
      displayName:
        type: "String" 
    resolveType: '@=resolver(''my_usertype_resolver'', [value])' # returns string 'LocalUser'

LocalUser:
  type: object
  inherits:
    - User
  config:
    fields:
      firstName:
        type: "String"
      lastName:
        type: "String"

However, when I send a query that has to do with these types, like:

{
  user(self: true) {
   displayName
  }
}

I get the following error:

{
"errors": [
    {
     "debugMessage": "Runtime Object type \"LocalUser\" is not a possible type for \"User\".",
     "message": "Internal server Error",
     "category": "internal",
     "locations": [
        {
         "line": 2,
         "column": 3
        }
     ],
     "path": [
        "user"
     ],
     "trace": [
        {
         "file": "\\My\\Project\\Location\\vendor\\webonyx\\graphql-php\\src\\Executor\\Executor.php",
         "line": 1106,
         "call": "GraphQL\\Executor\\Executor::ensureValidRuntimeType('LocalUser', GraphQLType: User, instance of ArrayObject(1), instance of GraphQL\\Type\\Definition\\ResolveInfo, instance of Acme\\Entity\\LocalUser)"
        },
        ...
     ],
     "data": {
        "user": null
     }
    }
}

Also when I use an inline-fragment, I get a slightly differently formulated error, though it essentially says the same:

{
  user(self: true) {
    displayName
    ... on LocalUser {
      firstName
    }
  }
}

{
  "errors": [
    {
      "message": "Fragment cannot be spread here as objects of type \"User\" can never be of type \"LocalUser\".",
      "category": "graphql",
      "locations": [
        {
          "line": 4,
          "column": 5
        }
      ]
    }
  ]
}

Things I tried which didn't work

• declaring User as object
  With this I can get fields of User, but still can't use inline-fragments to get fields of LocalUser (Fragment cannot be spread here as objects of type \"User\" can never be of type \"LocalUser\".")

• added heirs: [ LocalUser ] to User
  I tried this with User as interface as well as object, neither did work.

• explicitly declare LocalUser
  As described in the upgrade guide. Had no effect.

• clearing cache after all the above
  No effect.

[mcg-web]

Your LocalUser type only inherits of User type config (fields) this does not replace graphQL interface implementation. You still have to explicit declare that LocalUser implement User:

LocalUser:
  type: object
  inherits:
    - User
  config:
+   interfaces: [User]
    fields:
      firstName:
        type: "String"
      lastName:
        type: "String"

I'm closing this since it is not a bug but feel free to continue discussion if needed :+1:

[bastos71]

@mcg-web could you please update GraphQLBundle/docs/definitions/type-system/interface.md to introduce a basic usage example of an interface please ?

[mcg-web]

@bastos71 we have in plan to rewrite totally the documentation introducing some examples but we missing time right now, you can find a complete example here https://github.com/mcg-web/graphql-symfony-doctrine-sandbox/tree/master/src/AppBundle/Resources/config/graphql