Enable WASIP2 asyncio in guest #25
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Add wasip2 1.0 and futures 0.3 as dependencies to enable WASI Preview 2 async stream APIs and AsyncRead/AsyncWrite trait implementations needed for Cap'n Proto transports.
Replace synchronous echo with async implementation using WASI Preview 2 streams and polling. This enables non-blocking I/O that allows wasmtime to yield back to the host's Tokio runtime at WASI function call boundaries. Key changes: - Implement AsyncStdin wrapper with poll_read using stream.subscribe() and poll::poll() for non-blocking reads - Implement AsyncStdout wrapper with poll_write using blocking_write_and_flush() - Replace LocalPool with manual future polling using noop_waker - Fix EOF handling: return Poll::Ready(Ok(0)) when stream closes This maintains AsyncRead/AsyncWrite trait implementations for Cap'n Proto compatibility while preventing OS thread blocking.
Update documentation to reflect the async echo implementation using WASI Preview 2 streams. Document the AsyncRead/AsyncWrite trait implementations and their use for Cap'n Proto transports.
Prefix unused cx parameter with underscore to silence compiler warning. The parameter is required by the AsyncRead trait signature but not used since WASI polling handles waiting internally.
Replace find-based file discovery with explicit reference to default_kernel.wasm for better reliability and clarity. This ensures we always copy the correct WASM file produced by cargo.
- Fix default-kernel README: replace 'pollster' with 'manual future polling with noop_waker' - Update examples README: correct default-kernel description (async echo, not Cap'n Proto RPC) - Update requirements: clarify that examples have different dependencies - Update development guide: make ww dependency optional, clarify wasip2 feature usage
mikelsr
approved these changes
Nov 25, 2025
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🟢 Does what it says on the tin.
default-kernelupgraded to an asyncioechoexample.I plan to re-introduce your
guestmodule asap.