Add support for wasm32-unknown-unknown target#232
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tokio_postgres::Socket is not supported for wasm32-unknown-unknown target. tokio_postgres, additionally, may return a Connection type whose first bound is not a tokio_postgres::Socket. Accordingly, let's relax the bounds on try_from_client_and_connection so that we match the loosest type that may be returned by tokio_postgres's connection methods, which enables try_from_client_and_connection to work for a wasm32-unknown-unknown target.
weiznich
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May 9, 2025
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Thanks for opening this PR. Generally speaking I'm open to support this.
That written, there are a few things that I would like to clarify/improve before merging.
- The inline comments
- Changing the cfgs to rather use something like
#[cfg(target_family = "wasm")]instead to also support other wasm targets - Adding some test/example
- Adding some sort of CI check that this works. That should at least check if it compiles, ideally run all tests. Maybe diesel-rs/diesel#4411 could serve as an example for the testing?
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| #[cfg(not(target_arch = "wasm32"))] | ||
| fn establish(database_url: &str) -> impl Future<Output = ConnectionResult<Self>> + Send; |
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I would like to keep this method in all configuration.
It should be possible to provide an implementation for this for wasm32 as you somehow need to establish a connection there as well, right?
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| #[cfg(target_arch = "wasm32")] | ||
| wasm_bindgen_futures::spawn_local(async move { | ||
| match futures_util::future::select(shutdown_rx, conn).await { | ||
| Either::Left(_) | Either::Right((Ok(_), _)) => {} | ||
| Either::Right((Err(e), _)) => { | ||
| let _ = error_tx.send(Arc::new(e)); | ||
| } | ||
| } | ||
| }); | ||
|
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Given that the only difference here to the tokio::spawn call above is the name of the spawn function we maybe could refactor this to something like that to minimize code duplication:
let background_future = async move {
match futures_util::future::select(shutdown_rx, conn).await {
Either::Left(_) | Either::Right((Ok(_), _)) => {}
Either::Right((Err(e), _)) => {
let _ = error_tx.send(Arc::new(e));
}
}
};
#[cfg(not(target_arch = "wasm32"))]
tokio::spawn(background_future);
#[cfg(target_arch = "wasm32")]
wasm_bindgen_futures::spawn_local(background_future);
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tokio-postgresincludes support for targetingwasm32-unknown-unknown, and it would be wonderful to have ORM functionality with Diesel in WASM environments.This PR enables
diesel-asynccompilation with thepostgresfeature for thewasm32-unknown-unknowntarget. Please note that I have not explored what is required to supportwasm32-unknown-unknownfor other database or connection types.I am currently using this within a Cloudflare Workers deployment. (As an aside to anyone exploring, I have not yet been able to configure
diesel-asyncto work with Hyperdrive, presumably due to some Postgres feature set thatdiesel-asyncleverages and that Hyperdrive is not currently supporting. Usingdiesel-asyncwith a direct connection string without Hyperdrive, however, works as expected.)