Prevent onError from useMutation from being called in mutationCache

[joaopedrodcf]

Hey everyone thanks for this fantastic library!

I'm trying to understand whats the best way of error handleing globally in a react-query application

What I wanted was a way to prevent the useMutation onError from running when the mutationCache already ran for a specific error.

Example when there is a UNAUTHORIZED error after the createPostMutation is ran, I want to show the toast 'User not authorized' and I don't want to ran the onError of the useMutation

    const queryClient =  new QueryClient({
                mutationCache: new MutationCache({
                    onError: (error) => {
                        if (error instanceof CustomError) {
                            if (error.code === 'UNAUTHORIZED') {
                               toast({
                                   title: 'User not authorized',
                                });
                                
                                // If I retun a promise here the onError on useMutation will not run
                               // return new Promise();
                        }
                    },
                }),
            })
    );

   // useCreatePost

    const mutation = useMutation({
        mutationFn: createPostMutation,
        onSuccess: () => {
            toast({
                title: 'Success',
            });
        },
        onError: (error) => {
            if (error instanceof CustomError) {
                if (error.code === 'POST_ALREADY_EXISTS') {
                      toast({
                        title: 'Post already exists',
                       });
                       return;
                }
            }

            toast({
                title: 'Other problems but not a unauthorized error',
            });
        },
    });

One workaround that works is on the mutationCache return a promise.reject() this way the onError doesn't run his this the best way?

[TkDodo]

I noticed when I switch to another window, then back to the browser, it refetches, and I'm setting that option to false.

I don't think its meant to work that way but it's interesting that it does work 😅