Awaiting for mutation promise makes error and data undefined.

[Grsz]

If we have const [mutate, { data, error }] = useMutation(), and call mutate() alone, data, and error are populated as expected.

However, when awaiting the result of mutate like mutate().then(() => {}), data, and error are undefined.

I wouldn't expect this behaviour, and cannot seem to find it documented anywhere.

[phryneas]

Hi @Grsz,

we might need some more information here, so it would be great if you could share some more code.

That said, if your code snippet looks something like

const [mutate, { data, error }] = useMutation()

mutate().then(() => {
  console.log(data)
})

this is not a problem specific to Apollo Client - you are running into a stale closure:

Your .then function tries to access data of the scope that existed when the function was called. data here is a constant that will never update. Instead, on the next render, a new variable named data will exist in a different scope with a different value. That variable can never be accessed from that "old callback" that you defined with .then as it exists completely independently at a different point in time.

This is not an Apollo Client problem, it is a very common in React apps in general - in this case, if you need access to the new data, you will have to access the arguments passed into your .then function.