random incorrect response about graphql-tools

[helfer]

@bsr203 Looking just at the query and response it's really hard to tell. Can you show me the relevant part of your schema and how you're passing it to the server? Is node always a viewer? And is this using actual resolve functions, or are you using mocking?

[bsr203]

thanks for the quick response. I will try to get a reproducible case. Node is an interface with 9 implementations. I don't have any resolve/ custom mock function, but just the default mock by graphql-tools. Is there anything like sampling from 9 implementation? but anyway, I will try to make a reproducible case. thanks again.

[helfer]

Okay, so this could be due to the mocking indeed, because if you don't have resolve functions and don't specify the mocks then it will randomly pick one of the implementing types for the interface. Since you only ask for a fragment on the Viewer type, the response will come back empty in 8 out of 9 cases, because Viewer is only one of the 9 types.

[bsr203]

so, is it feasible to identify the fragment type and mock appropriately by graphql-tools, or it should be the responsibility of the user to provide a resolve function? Do you have any rough sketch or any example/test case to point to. thanks again.

[helfer]

I think looking into fragments to decide what interface gets mocked would make things a bit more complicated, but it shouldn't be too hard to do. One thing to keep in mind however is that what you're getting right now is a completely valid GraphQL response, so your program should be able to deal with it.
If you want to mock only a certain type of the interface, one way to go about it would be to specify the node mock and return an object with { typename: "Viewer"}. I'm not 100% sure, but believe that would give you what you want.

You can find a test case in the test folder, just search for interface. The actual implementation is in mock.js

[bsr203]

thank you. I will close this now, as you said, it is a valid response. Will try out the options you suggested and get back with you. thanks again.