introduce new intersection type #941
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sorry, did I miss something, a lot maybe? - where's the discussion? Straight PR into spec? |
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alternative to #939 |
This is a continuation of/alternative to the "unions implementing interfaces" work I presented at the last WG. |
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| @@ -343,6 +343,19 @@ UnionTypeExtension : | |||
| - extend union Name Directives[Const]? UnionMemberTypes | |||
| - extend union Name Directives[Const] | |||
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| IntersectionTypeDefinition : Description? intersection Name Directives[Const]? | |||
| IntersectionMemberTypes? | |||
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so IntersectionMemberTypes element is optional? we can have intersection with empty list of types?
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It is same as Union it could be extended later. So valid to be empty initially in sdl. When validated, it has to be non/empty if I recall correctly, just like unions. But we do allow an intersection with non empty list of member types and currently empty list of possible types due to conflict.
Just like interfaces without implementing types are allowed. I believe :)
| claims it returns an Intersection type, it will return only types that are | ||
| contained within all of the Intersections's Unions and types that implement all | ||
| of the Intersection's Interfaces. | ||
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- what is Intersection's Unions? in the grammar rule you mention IntersectionMemberTypes
- so... if at runtime field resolver returns a value of type that IS one of union types but does not implement one of interfaces - then what? it is replaced with null? what if field is not nullable? Hell confusing
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At runtime, only concrete object types can be returned as the actual type just like with any other abstract type.
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And yes, an intersection's unions are its member types that are unions. I copied the grammar from unions where even though object types are the only currently allowed member types, that is not specified at the grammar level, it's specified only as part of validation.
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If a non possible type is returned at runtime you get the same error as if you return a non implementing type when using an interface or an object type not in the Union.
In the implementation changes, there was no need to directly touch Execution because the only thing that changes is what goes on in the isSubType method
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Summary of discussion from WG https://github.com/graphql/graphql-wg/blob/main/agendas/2022/2022-05-05.md :
The action item will then be to move forward as possible with #939 . Immediate next steps is to refine the implementation at graphql/graphql-js#3527 with further checking for all the necessary validation and test changes. |
see graphql/graphql-js#3550
[Edit by @benjie]: Explanation/discussion at graphql/graphql-wg#944