Can I use use the this parameter on callbacks such as onMutate and mutationFn?

[tringenbach]

I am looking for a way to access from inside my default mutationFn some options that I set when I call useMutation().

I noticed that if I use a function keyword function (and not an arrow function, of course), the this parameter inside onMutate and mutationFn have the fields I need!

But, I couldn't find that documented anywhere. So I would like to know if this is something I can rely on, or if it is more of an accident that could change at any time.

(Unfortunately I was having trouble searching for this, since it's such as a generic word.)

Is it safe to access this from mutationFn?

If not, is there any other way to get at the options passed to useMutation() from inside the mutationFn?