Also import `ScopeStorage` from `Base` with Julia >= 1.11

[Drvi]

While migrating from ContextVariablesX.jl, we needed an "empty scope" in place of empty ContextSnapshot{T}. To do that in a way that is works both before and after Julia 1.11, we needed this hack:

const _EMPTY_SCOPE = ScopedValues.Scope(
    isdefined(ScopedValues, :ScopeStorage) ?
        ScopedValues.ScopeStorage() :
        Base.ScopedValues.ScopeStorage()
)

Since ScopeStorage is not imported to the package from Base in 1.11.
Could we please import it?:)

[vchuravy]

Why do you need an empty Scope? Scope is not something user-facing and I would like to examine the pattern first,
before we commit to supporting something.

[Drvi]

Hey Valentin, sure -- we have a TaskGroup construct that runs "TaskQueueEntries" (which are similar to Base.Tasks) according to their priority, and we store the scope in each of these TaskQueueEntries like this:

task_scope = @something(ScopedValues.current_scope(), _EMPTY_SCOPE)

When running our task, we reconstruct the scope using enter_scope (and its variant for Julia 1.11+).

[vchuravy]

Enter_scope is not public and we need to be careful with the semantics here. Long-term I want to be able to support compiler optimization over scoped values and letting the user manipulate the scope directly would break those.

We can discuss snapshotting (x-ref #6), but I am not comfortable with user packages directly manipulating the internals.

[Drvi]

Gotcha, thanks, too bad there seems to be no way to implement snapshotting in userspace. Any time estimate for the snapshotting feature to be finalized? Once done, would it be possible to snapshot the current_scope()? Any way I could help?

[vchuravy]

@Drvi I think the best thing would be to help with #6

E.g. if we implement snapshotting here instead in your code basis we can make sure that it doesn't break semantics

[kpamnany]

We think #24 will satisfy our needs (so far so good!) so this can probably be closed. Attn: @Drvi.