Refactor AsyncData/AsyncError with isLoading:true to AsyncLoading instead

[rrousselGit]

During refresh, it was made so that instead of emitting an AsyncLoading, the provider would emit an AsyncData/AsyncError corresponding to the previous state; but with isLoading=true/isRefreshing=true.

This was due to an implementation detail of how AsyncValue.when/map work.
But this impacts features like whenData/asData negatively. From experience, this is confusing to folks.

We could fix that behaviour such that an AsyncLoading is always emitted, with either isRefreshing or isReloading set.

Considerations

We'd have to double check how this impacts pattern matches.

Currently folks can do:

switch ()
  AsyncData(:final value) =>,
  AsyncError(:final error) =>,
  _ =>,

which will show previous data during refreshes but not show previous data during reloads.
This wouldn't behave like this anymore with the new behavior, and would instead show data/error only once they completed.

To match this behavior, folks would have to do:

switch ()
  AsyncValue(:final value?, isReloading: false) =>,
  AsyncValue(:final error?, isReloading: false) =>,
  _ =>,

Omitting the isReloading: false would have the switch show data/error during reloads (ref.watch updates).

[AhmedLSayed9]

LGTM.

[mboyamike]

Curious, is there a way of matching the behaviour if value is nullable?

[rrousselGit]

You can use hasData

AsyncValue(:final value, hasData: true, isReloading: false)

[woprandi]

I discovered recently AsyncLoading is emitting for a reload / rebuild (with hasValue to true) but AsyncData for a refresh (ref.refresh / ref.invalidate). I think it's not very consistent and I feel both behavior should be close

EDIT : with old syntax AsyncValue.when() we had skipLoadingOnReload and skipLoadingOnRefresh to handle these cases so this behavior is less opaque

[jeanlucthumm]

@woprandi I don't understand the difference between reload vs refresh.

Would reload / rebuild be when the provider is disposed and we are later calling it again? But then how can the loading state have a value, given it was disposed?

[rrousselGit]

Coming back to this:
I'm not sure a change is truly desirable

The main reason for the current design is so that we can do:

switch (asyncValue) {
  AsyncData(:final value) => 'data'
  AsyncError(:final error) => 'error',
  _ => 'loading',
}

Where the loading is skipped during ref.refresh but shown when caused by ref.watch (aka refresh vs reload)`