Can't format error | onError doesn't get called

[UchihaYuki]

Screenshot

Expected Behaviour
I hope when an error is thrown, onError can get called.

Actual Behaviour
never get called

Debug Information
Help us debug the bug?

Further Information
Anything else you might find helpful.

[enisdenjo]

That is because onError is not handling exceptions in the subscription iterator. There is an open discussion in graphql-js about what to do.

You can read more and handle the thrown error gracefully following the "ws server usage with custom subscribe method that gracefully handles thrown errors" recipe.