What is the advantage of the useMutation callbacks over the native Promise syntax?

[githorse]

Why do we need callbacks on useMutation? Is there a distinction between

const {mutate} = useMutation({
  mutationFn: cat => post(`/cats`, cat),
  onSuccess: cat => toast.success('Made a cat')
})

and

const {mutate} = useMutation({
  mutationFn: cat => post(`/cats`, cat)
    .then(cat => toast.success('Made a cat'))
})

Related to #2651, but there the difference comes down to the way promise rejections are handled, which (I don't think?) is relevant here.

[TkDodo]

you can use both, there isn't a big difference. The callbacks are nice to read, and they can be overwritten if you use an abstraction where the mutationFn is provided for you, like with trpc. Or, if you have a defaultMutationFn.

[githorse]

Worth noting one other distinction is that, with the native promise version, you need to be sure that any .then() returns the original data in order for the mutation function to make sense:

// ❌ bad
mutationFn: cat => post(`/cats`, cat).then(cat => toast.success('Made a cat'))

// ✔️ good
mutationFn: cat => post(`/cats`, cat).then(cat => {toast.success('Made a cat'); return cat})