Type checking not working for resolver return values

[elie222]

Using the recipe example, the following should throw a TS error, but doesn't:

@ObjectType()
class Recipe {
  @Field(type => ID)
  id: string;

  @Field()
  title: string;
}

@Resolver(Recipe)
export class RecipeResolver {
  @Query(returns => Recipe)
  async recipe(@Arg("id") id: string) {
    return {}; // expected to throw a TS error as it doesn't have the `id` or `title` properties, but works fine!
  }
}

Running the following query in GraphQL Playground does throw an error as expected:

{
  recipe(id: "123") {
    id
    title
  }
}

Error:

{
  "errors": [
    {
      "message": "Cannot return null for non-nullable field Recipe.id.",
      "locations": [
        {
          "line": 3,
          "column": 5
        }
      ],
      "path": [
        "recipe",
        "id"
      ],
      "extensions": {
        "code": "INTERNAL_SERVER_ERROR",
        "exception": {
          "stacktrace": [
            "Error: Cannot return null for non-nullable field Recipe.id.",
          ]
        }
      }
    }
  ],
  "data": null
}

[MichalLytek]

The @Field(type => [Rate]) is only for providing type info when there's not enough TypeScript's reflection metadata. It doesn't perform the typechecking - the proposal is described in issue #221.

To have a type checking, you have to provide an explicit type annotation (e.g. : Promise<Recipe>):

  @Query(returns => Recipe)
  async recipe(@Arg("id") id: string): Promise<Recipe> {
    return {}; // throw a TS error
  }