Make QueryClientConfig generic

[SevenOutman]

Current declaration for QueryClientConfig makes it impossible to specify an TError type for DefaultOptions.
https://github.com/tannerlinsley/react-query/blob/0c667273125e5307ff148c0ce621b5d24950517f/src/core/types.ts#L679-L688

This makes things hard when your TError is certain, e.g. AxiosError.

I'd suggest make QueryClientConfig generic that accepts a TError type argument.

export interface QueryClientConfig<TError = unknown> { 
   queryCache?: QueryCache 
   mutationCache?: MutationCache 
   defaultOptions?: DefaultOptions<TError>
 } 
  
 export interface DefaultOptions<TError = unknown> { 
   queries?: QueryObserverOptions<unknown, TError> 
   mutations?: MutationObserverOptions<unknown, TError, unknown, unknown> 
 } 

[TkDodo]

This makes things hard when your TError is certain, e.g. AxiosError.

is it though? I don't think you can be certain of that. For example, if you have a runtime error in select, your query will also go into Error state with that error. A simple instanceOf Error check, or to use a runtime type guard from axios (axios.isAxiosError(error)) is one line of code.

https://tkdodo.eu/blog/react-query-and-type-script#what-about-error

[SevenOutman]

You're right. I didn't realize that select error also triggers onError. But yes I still missed the point that queryFn may throw any runtime error as well. Thanks!

[SevenOutman]

Hi @TkDodo, I just couldn't think up why DefaultOptions has this TError arg then?

[TkDodo]

yeah I also don't know because we never use that generic. Maybe we should just remove it?