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so yea, probably you'd want to create a value wrapping a Snapshot ?

How on the Python side would I take that `Value` and hydrate it into a `Snapshot` Python object? Given I’ve already called the constructor that we _do_ pass through to the Rust

```    c = ffi.from_handle(context_handle)
    thing = c.from_value(thing_val)```

<@U06A03HV1> Next up… scheduler_test_base… Currently has an unused `context_with_scheduler` function, which calls `self.context` which doesn’t exist…

(i need to refresh and land the base test review. sigh.)

You answered my question! :stuck_out_tongue:

IIRC it landed, reverted, and didn’t re-land

the current issue is the MDB resource constraint one.

schedulers either leaking or just not be torn down quickly enough during tests.

rebasing now, because perhaps that is sufficiently resolved at this point.

Have you rebased past that time I divided the VIRT by 10?

er, nope. false. the RFC has been merged... no implementation yet. sorry.

i actually wonder whether async/await in nightly is a thing that we should legitimately get on and help to give feedback on. it's so fundamental.

I’d be up for trying async/await :slightly_smiling_face:

So… Variants… Do they work today? If so, how? What exactly do they do?

they do not work today. but they're described in the engine readme

they worked for the purposes of experiments, but while productionizing the rust code they bitrotted because we didn't need them to fill the BuildGraph API

the issue mentioned in <https://github.com/pantsbuild/pants/issues/5788> is a pretty fundamental weakness of how they were implemented, so i think there is some design work needed there to nail that down.

When you say the engine readme… It’s not in <https://github.com/pantsbuild/pants/blob/master/src/rust/engine/README.md> or <https://docs.google.com/document/d/1C64MreDeVoZAl3HrqtWUVE-qnj3MyWW0NQ52xejjaWw/edit?usp=sharing> which it links to…

Do you have an opinion on fixing variants vs removing them and writing something from scratch (which may look similar) to solve concrete use-cases?

<https://github.com/pantsbuild/pants/blob/master/src/python/pants/engine/README.md>

more cost to remove than to replace, i think

Is there a handy existing way in rust to lift a `Snapshot` from a `Value` which points to one? The `Vec` of multiply nested `PathStat` structure is a little annoying to be writing a `lift` implementation for, but if one exists already…

Sigh. I suspect it’s going to be non-trivial :disappointed:

on the bright side, the idea of having exactly one concept for "caller provided parameters" is pretty exciting.

<@U06A03HV1> Sadly I still can’t Snapshot -&gt; FilesContent… Any easy tips for how to fix `No installed rules can satisfy Select(Collection.of(FileContent)) for a root subject of type Snapshot`?

If I blindly install a `RootRule(Snapshot)` I instead get a `Throw("No task was available to compute the value.")`… So I guess that’s progress…

It looks like it’s doing `select_literal_single` checks to see whether the `Snapshot` is any of:
`FilesContent`, `PathGlobs`, `HasProducts`