'idle' state (removal) in v4 - queries vs. mutations

[targumon]

First of all, thanks for the great v4 migration guide! 🙏

One of the things I liked is the streamlining of Queries & Mutations (e.g. auto garbage collection for mutations just like for queries, or aligning their NotifyEvents).

Which is why I was surprised to see their statuses diverge:

export type QueryStatus = 'loading' | 'error' | 'success'
export type MutationStatus = 'loading' | 'error' | 'success' | 'idle'

I totally understand why 'idle' was removed from Queries.
But now that I have to fix a small bit of my code (because I assumed the types are compatible and they no longer are - it's a small fix, no hassle), I was just wondering if it wasn't supposed to be removed from Mutations as well. 🤔

WDYT?

[TkDodo]

queries and mutations are fundamentally different. mutations don't have a fetchStatus like queries do. Every mutation starts off in idle state, while only a small amount of queries did actually start out in idle state.

When we introduced the fetchStatus for queries, the idle state stood out because it couldn't be combined with certain fetch states. For example, you couldn't be idle and paused - that didn't make sense.

So while unification is generally good, I think we have two different cases here that justify the differences.