ApiApp throws exception when endpoints return un-JSON-serializable data

[robertklep]

When an ApiApp instance calls an API endpoint (of another app), and that endpoint returns something that cannot be JSON-serialized (like undefined), an exception is thrown by ApiApp (Error: invalid json response body at Remote Process).

It's not documented anywhere that API endpoints should return data that's JSON-serializable.

[tjallingt]

Nice, thanks for reporting!

Do I understand correctly this error happens in the app that performs the call (client), not the one providing the data (server)?
In that case I think we should also print a warning when an api returns data that doesn't json serialize, so the developer of the app in question can spot, and fix, it more easily.

[robertklep]

Correct, the client gets the exception.

Warning on the server side sounds like a good idea 👍🏻

[tjallingt]

So actually the issue was that we internally turn undefined into a 204 No Content response but the client tried to parse that as JSON. I added a check so that a 204 status code gets turned back into undefined as expected. I'm going to take a look at the documentation and see if we can explain this behaviour clearer.