add initialDataUpdatedAt

[Nadelopo]

#292
I suggest adding initialDataUpdatedAt as in tanstack. otherwise it is not clear how use Query with initialData

[posva]

What isn't clear?

[Nadelopo]

example from 292.
I want the cache time to be 5 minutes, and I want a refetch when count changes. How can I achieve this? placeholderData is not an option because a default state is usually always needed to avoid errors where data might be undefined.
In tanstack you can use initialDataUpdatedAt: 0, then the request will be sent immediately at initialization, and subsequent requests will be sent when the key is changed.

[posva]

Where is placeholder data failing?

[Nadelopo]

placeholder means that the value can be undefined. this is inconvenient if you get an array of posts, you want the initial value to be an empty array, if it is undefined you will have to do constant checks on the value.

posts.value?.[index] 
if(!post.value) return

its annoying

[posva]

Thats not correct. It’s what I have been trying to tell you all this time 😅

[Nadelopo]

what is not correct?

[posva]

Value cannot be undefined with placeholder

[Nadelopo]

???

[posva]

I remember there are cases where the data can be undefined so it’s typed accordingly (https://github.com/posva/pinia-colada/blob/main/src/use-query.test-d.ts#L238) but IIRC it was always be defined in the demo you shared

Edit: I remember it now: it’s because the fetch can error and in that case the data will be undefined