In what circumstances is context not passed from onMutate to onSuccess?

[RazerM]

I apologise if this has previously been discussed, there are a lot of search results for "context" so I may have missed something.

The type of the useQuery callbacks (onSuccess/onError/onSettled) have context: TContext | undefined.

If my onMutate function returns a type T, is that not guaranteed to be passed to the context parameter of the callbacks?

[TkDodo]

onMutate is async, so it can return a failed / rejected promise, so the return part is never reached if that happens.

[RazerM]

Thanks, so that's clear for onError and onSettled then. If there's nothing else, I think on the onMutate type could be changed from

query/src/core/types.ts

Lines 545 to 547 in 5e37b14

	onMutate?: (
	variables: TVariables
	) => Promise<TContext | undefined> | TContext | undefined

to

  onMutate?: (
    variables: TVariables
  ) => Promise<TContext> | TContext

which would allow onSuccess to be

  onSuccess?: (
    data: TData,
    variables: TVariables,
    context: TContext
  ) => Promise<unknown> | void

onError and onSettled would maintain TContext | undefined obviously.

[RazerM]

It would be nice to document this too, that context may only be undefined if onMutate throws/rejects (unless TContext includes undefined of course)

I could contribute this if my proposed changes aren't invalid.

[TkDodo]

I think on the onMutate type could be changed

I think you are right. would you like to try this in a PR ?