feat: support the wasm32-unknown-emscripten target - #8281
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Motivation
Tokio does not yet support the
wasm32-unknown-emscriptentarget, which is widely used in the WebAssembly ecosystem. This PR initiates a first step towards that.Solution
Supports the single-threaded
wasm32-unknown-emscriptenwithwasm32-unknown-unknownparity:sync,macros,io-util,rt,time, andtest-utilcompile and work.process/signalare compiled out (nofork/execor kernel signal delivery) and the multi_thread flavor is rejected.netremains unsupported (pending the Mio PR in tokio-rs/mio#1969).This is just an initial minimal target support PR, to follow-up on next with the JSPI-based parking and hosted event loop models afterwards. As such, it has no execution-model changes and no design decisions beyond existing Wasm target policy. A
block_onwhose future cannot resolve synchronously behaves as on the other single-threaded Wasm targets.CI runs the
sync/macrostest surface under Node.js, just likewasm-bindgen-test, and checks every supported feature combination for the target.//cc @Darksonn @Noah-Kennedy