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refactor {Stream,Future}|{Reader,Writer} APIs and internals #11325

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Merged
alexcrichton merged 3 commits into from
Jul 30, 2025
Merged

refactor {Stream,Future}|{Reader,Writer} APIs and internals #11325

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4194e0a
refactor `{Stream,Future}|{Reader,Writer}` APIs and internals
dicej Jul 17, 2025
f1450b8
lower host stream/future writes in background task
dicej Jul 30, 2025
74ee080
fix `tcp.rs` regressions
dicej Jul 30, 2025
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16 changes: 9 additions & 7 deletions crates/misc/component-async-tests/src/resource_stream.rs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,7 @@
use anyhow::Result;
use wasmtime::component::{Accessor, AccessorTask, HostStream, Resource, StreamWriter};
use wasmtime::component::{
Accessor, AccessorTask, GuardedStreamWriter, Resource, StreamReader, StreamWriter,
};
use wasmtime_wasi::p2::IoView;

use super::Ctx;
Expand Down Expand Up @@ -36,31 +38,31 @@ impl bindings::local::local::resource_stream::HostWithStore for Ctx {
async fn foo<T: 'static>(
accessor: &Accessor<T, Self>,
count: u32,
) -> wasmtime::Result<HostStream<Resource<ResourceStreamX>>> {
) -> wasmtime::Result<StreamReader<Resource<ResourceStreamX>>> {
struct Task {
tx: StreamWriter<Option<Resource<ResourceStreamX>>>,
tx: StreamWriter<Resource<ResourceStreamX>>,

count: u32,
}

impl<T> AccessorTask<T, Ctx, Result<()>> for Task {
async fn run(self, accessor: &Accessor<T, Ctx>) -> Result<()> {
let mut tx = self.tx;
let mut tx = GuardedStreamWriter::new(accessor, self.tx);
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@alexcrichton alexcrichton Jul 29, 2025

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Think about this in the context of rebasing with wasi:sockets -- is this necessary? Tasks can only be cancelled for two reasons:

  1. The store is dropped - in this case there's no need to do further cleanup
  2. The AbortHandle is triggered, but in this case it's statically known we just forget about that and ignore it.

Given that does WASI actually need Guarded*?

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@dicej dicej Jul 29, 2025

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Perhaps we don't need it, but it saves us from having to remember to close the handle explicitly before returning, which isn't too onerous for this simple task, but could become a maintenance hazard later.

wasmtime-wasi-http has some pretty complicated control flow, where keeping track of what to close when without RAII would be a real pain.

for _ in 0..self.count {
let item =
accessor.with(|mut view| view.get().table().push(ResourceStreamX))?;
tx.write_all(accessor, Some(item)).await;
tx.write_all(Some(item)).await;
}
Ok(())
}
}

let (tx, rx) = accessor.with(|mut view| {
let instance = view.instance();
instance.stream::<_, _, Option<_>>(&mut view)
instance.stream(&mut view)
})?;
accessor.spawn(Task { tx, count });
Ok(rx.into())
Ok(rx)
}
}

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