postMessage support
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Module workers are now widely available, and assuming modules allows us to use `import.meta.url` to get the shim script URL directly rather than dynamically generating the script with a value injected. This results in a significantly more bundler-friendly experience, as well as letting us make use of `wasm_thread` in environments where dynamic code execution is not available, such as WebExtensions.
This allows us to run async code on the worker thread. A two-stage approach is used: first, a `Send` function is passed to the thread, which is executed to obtain a non-`Send` future. This supports the ‘work-dealing’ pattern in which the task is first moved to another thread, and then kept there whilst running.
Remove the spawn request functionality, since nested Web workers are now widely supported in browsers. This allows us to return a `Worker` directly that we can post messages to.
jvff
approved these changes
Nov 4, 2024
| scope_data: Option<Arc<ScopeData>>, | ||
| ) -> std::io::Result<JoinInner<'scope, T>> | ||
| ) -> std::io::Result<(Thread, JoinInner<'scope, Fut::Output>)> |
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Nit: would it make sense to return the JoinHandle directly here?
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In order to pass JavaScript objects like shared array buffers or WebAssembly modules into the thread, we need to be able to clone them across with the
structuredClonealgorithm, i.e. by usingpostMessage.In a slightly hacky way, this PR:
es_modulesfeature — for complicated bundler reasons it was a pain to get this working with modules, it would have required a different approach for non-modules, and module worker support is now widespreadasynccode in the spawned thread — this has to happen here because weclose()the worker as soon as the function arrives, so the worker entrypoint has to be async-aware to not close the thread too soonWorkerobject when we spawn as part of theJoinHandleso we canpost_messageto it later