Change from undefined to null doesn't run queryFn

[dmitry-seemetrics]

React-query doesn't run queryFn if queryKey changed from undefined to null or from null to undefined.
From our backend perspective it is different things, undefined - means you didn't send value, null means you set it to null (empty)
Example
What can I do if my queryKey needs to change fron undefined to null for example?

[TkDodo]

Our internal query key hashing is based on JSON.stringify, which will yield '[null]' for both [null] and [undefined].

If that's an issue for you, you can provide your own queryKeyHashFn. You can also do that globally as a default option.

The docs say:

When a query needs more information to uniquely describe its data, you can use an array with a string and any number of serializable objects to describe it. This is useful for:

but I agree that could be described a bit better. If you want, please file a PR to update the docs?

https://tanstack.com/query/latest/docs/react/guides/query-keys#query-keys-are-hashed-deterministically

[wpp-roman-gryndii]

@TkDodo I have another issue related to hashing

I have an endpoint /messages?maxIndex=number|undefined

I am changing this parameter in the key dynamically from
['QUERY_KEY', { parameter: 777 }] > ['QUERY_KEY', { parameter: undefined }]

And then call query.refetch() it is being re-fetched with the previous value 777 instead of undefined

is that expected?

[TkDodo]

show a reproduction please, might be related to:

• Query keys with object property set to undefined are not considered equal to missing property during invalidation #3741