Comments (27)
khuey
commented on May 31, 2024
Try conn.prepare(blahblahblah).compat().then(do_stuff)?
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Texlo-Dev
commented on May 31, 2024
Okay. Now, with the following function:
async fn try_cmd(mg: Message, mut args: Args, state: Arc<State>) -> Result<()> {
state.postgres.run(|mut conn| {
conn.prepare("SELECT slot_1, slot_2, slot_3 FROM loadouts WHERE user_id = $1")
.compat()
.then(|st| {
let query = conn.query(&st.unwrap(), &[&(mg.author.id.0 as i64)]);
// Work with query
Ok(())
})
});
Ok(())
}I get the following:
error[E0277]: the trait bound `std::result::Result<(), _>: core::future::future::Future` is not satisfied
--> src/commands/loadout.rs:38:14
|
38 | .then(|st| {
| ^^^^ the trait `core::future::future::Future` is not implemented for `std::result::Result<(), _>`
error[E0277]: the trait bound `futures_util::future::then::Then<futures_util::compat::compat01as03::Compat01As03<tokio_postgres::impls::Prepare>, std::result::Result<(), _>, [closure@src/commands/loadout.rs:38:19: 41:14 conn:_, mg:_]>: futures::future::Future` is not satisfied
--> src/commands/loadout.rs:35:20
|
35 | state.postgres.run(|mut conn| {
| ^^^ the trait `futures::future::Future` is not implemented for `futures_util::future::then::Then<futures_util::compat::compat01as03::Compat01As03<tokio_postgres::impls::Prepare>, std::result::Result<(), _>, [closure@src/commands/loadout.rs:38:19: 41:14 conn:_, mg:_]>`
|
= note: required because of the requirements on the impl of `futures::future::IntoFuture` for `futures_util::future::then::Then<futures_util::compat::compat01as03::Compat01As03<tokio_postgres::impls::Prepare>, std::result::Result<(), _>, [closure@src/commands/loadout.rs:38:19: 41:14 conn:_, mg:_]>`
I'd ultimately want to port this code to async/await if possible. Any suggestions here?
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khuey
commented on May 31, 2024
You should probably read https://jsdw.me/posts/rust-asyncawait-preview/. I think rather than using the compat method you should import the futures 0.1 Future trait and convert only to a new style future at the outermost layer (the state.postgres.run)
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khuey
commented on May 31, 2024
Feel free to keep commenting but because this is not actually a bug in bb8 I'm going to close this issue.
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Texlo-Dev
commented on May 31, 2024
@khuey I know this isn't an issue with bb8, but would you have a clue on how to get a solution like async/await working?
From the guide you mentioned, it says that you can use the tokio::await!() to convert an old style future to a new stylle future. So I've done something like this:
fn execute(&self, mg: Message, args: Args, state: Arc<State>) {
tokio::run_async(async move {
let mut resp = CommandResponse::new(mg.channel_id.0, state);
await!(resp.text("Testing my Text").execute()).unwrap();
tokio::await!(state.postgres.run(async move |mut conn| {
let stmt = tokio::await!(conn.prepare("SELECT slot_1, slot_2, slot_3 FROM loadouts WHERE user_id = $1"))?;
let query = conn.query(&stmt, &[&(mg.author.id.0 as i64)]);
await!(resp.text("Testing my Text").execute())?;
}))
Ok(())
});
}However, I am greeted with this error:
error[E0271]: type mismatch resolving `<impl core::future::future::Future as core::future::future::Future>::Output == ()`
--> src/commands/help.rs:27:9
|
27 | tokio::run_async(async move {
| ^^^^^^^^^^^^^^^^ expected enum `std::result::Result`, found ()
|
= note: expected type `std::result::Result<(), _>`
found type `()`
= note: required by `tokio::run_async`
error[E0277]: the trait bound `impl core::future::future::Future: tokio::prelude::Future` is not satisfied
--> src/commands/loadout.rs:31:42
|
31 | tokio::await!(state.postgres.run(async move |mut conn| {
| ^^^ the trait `tokio::prelude::Future` is not implemented for `impl core::future::future::Future`
|
= note: required because of the requirements on the impl of `tokio::prelude::IntoFuture` for `impl core::future::future::Future`
error[E0271]: type mismatch resolving `<impl core::future::future::Future as core::future::future::Future>::Output == ()`
--> src/commands/loadout.rs:28:9
|
28 | tokio::run_async(async move {
| ^^^^^^^^^^^^^^^^ expected enum `std::result::Result`, found ()
|
= note: expected type `std::result::Result<_, _>`
found type `()`
= note: required by `tokio::run_async`
Am in misinterpreting something here?
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khuey
commented on May 31, 2024
You should unwrap (or actually handle errors) from the await! and then get rid of the Ok(()) at the end.
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Texlo-Dev
commented on May 31, 2024
Right now, I'm currently at this error.
error[E0277]: the trait bound `impl core::future::future::Future: tokio::prelude::Future` is not satisfied
--> src/commands/loadout.rs:44:34
|
44 | tokio::await!(state.postgres.run(async move |mut conn| {
| ^^^ the trait `tokio::prelude::Future` is not implemented for `impl core::future::future::Future`
|
= note: required because of the requirements on the impl of `tokio::prelude::IntoFuture` for `impl core::future::future::Future`
error: aborting due to previous error
For more information about this error, try `rustc --explain E0277I feel like its something to do with the run() method not directly returning a future?
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khuey
commented on May 31, 2024
postgres.run wants an old style future, not the async stuff. I think you can just get rid of the async keyword there and fix up the return value.
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Texlo-Dev
commented on May 31, 2024
Problem with that being, I want to be able to use the await macro inside, since I have async operations that rely on the result from the query.
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khuey
commented on May 31, 2024
Ok, then follow the steps in the article that I linked about converting from a new style future to an old style one?
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Texlo-Dev
commented on May 31, 2024
Well I ended up doing that.
Now I need to fix to return value to what?
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khuey
commented on May 31, 2024
Idk, what errors do you have now?
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Texlo-Dev
commented on May 31, 2024
error[E0277]: the trait bound `(): core::future::future::Future` is not satisfied
--> src/commands/loadout.rs:47:10
|
47 | .then(move |st| {
| ^^^^ the trait `core::future::future::Future` is not implemented for `()`
error[E0277]: the trait bound `futures_util::future::then::Then<futures_util::compat::compat01as03::Compat01As03<tokio_postgres::impls::Prepare>, (), [closure@src/commands/loadout.rs:47:15: 49:10 conn:_, mg:_]>: tokio::prelude::Future` is not satisfied
--> src/commands/loadout.rs:44:34
|
44 | tokio::await!(state.postgres.run(move |mut conn| {
| ^^^ the trait `tokio::prelude::Future` is not implemented for `futures_util::future::then::Then<futures_util::compat::compat01as03::Compat01As03<tokio_postgres::impls::Prepare>, (), [closure@src/commands/loadout.rs:47:15: 49:10 conn:_, mg:_]>`
|
= note: required because of the requirements on the impl of `tokio::prelude::IntoFuture` for `futures_util::future::then::Then<futures_util::compat::compat01as03::Compat01As03<tokio_postgres::impls::Prepare>, (), [closure@src/commands/loadout.rs:47:15: 49:10 conn:_, mg:_]>`
error: aborting due to 2 previous errors
This is using the compat() way to be able to return a futures 0.1 future.
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khuey
commented on May 31, 2024
And what's in the then closure?
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Texlo-Dev
commented on May 31, 2024
.then(move |st| {
let query = conn.query(&st.unwrap, [&(mg.author.id.0 as i64)]);
})from bb8.
khuey
commented on May 31, 2024
The return value of that closure needs to be a future. Also you're not actually calling unwrap, and you wouldn't need it at all if you used and_then instead of then for this closure.
Try something like
.and_then(move |st| {
conn.query(&st, [&(mg.author.id.0 as i64)])
})from bb8.
Texlo-Dev
commented on May 31, 2024
@khuey Sorry about the delay,
So this is what we have now:
async fn my_cmd(mg: Message, mut args: Args, state: Arc<State>) -> Result<()> {
let mut resp = CommandResponse::new(mg.channel_id.0, state);
await!(resp.text("Testing my Text").execute())?;
tokio::await!(state.postgres.run(move |mut conn| {
conn.prepare("SELECT slot_1, slot_2, slot_3 FROM loadouts WHERE user_id = $1")
.compat()
.and_then(move |st| {
let query = conn.query(&st, &[&(mg.author.id.0 as i64)]);
})
}));
Ok(())
}This yields the following:
|
47 | .and_then(move |st| {
| ^^^^^^^^ the trait `core::future::future::Future` is not implemented for `()`
|
= note: required because of the requirements on the impl of `futures_core::future::TryFuture` for `()`
error[E0277]: the trait bound `futures_util::try_future::and_then::AndThen<futures_util::compat::compat01as03::Compat01As03<tokio_postgres::impls::Prepare>, (), [closure@src/commands/loadout.rs:47:19: 49:10 conn:_, mg:_]>: tokio::prelude::Future` is not satisfied
--> src/commands/loadout.rs:44:34
|
44 | tokio::await!(state.postgres.run(move |mut conn| {
| ^^^ the trait `tokio::prelude::Future` is not implemented for `futures_util::try_future::and_then::AndThen<futures_util::compat::compat01as03::Compat01As03<tokio_postgres::impls::Prepare>, (), [closure@src/commands/loadout.rs:47:19: 49:10 conn:_, mg:_]>`
|
= note: required because of the requirements on the impl of `tokio::prelude::IntoFuture` for `futures_util::try_future::and_then::AndThen<futures_util::compat::compat01as03::Compat01As03<tokio_postgres::impls::Prepare>, (), [closure@src/commands/loadout.rs:47:19: 49:10 conn:_, mg:_]>`
error: aborting due to 2 previous errors
For more information about this error, try `rustc --explain E0277`.
So if I understand correctly, I have to return a future in the .and_then() closure as well?
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khuey
commented on May 31, 2024
Right. Try something like this:
async fn my_cmd(mg: Message, mut args: Args, state: Arc<State>) -> Result<()> {
let mut resp = CommandResponse::new(mg.channel_id.0, state);
await!(resp.text("Testing my Text").execute())?;
let results = tokio::await!(state.postgres.run(move |mut conn| {
conn.prepare("SELECT slot_1, slot_2, slot_3 FROM loadouts WHERE user_id = $1")
.then(move |r| {
match r {
Ok(st) => {
conn.query(&st, &[&(mg.author.id.0 as i64)])
.then(move |r| {
match r {
Ok(results) => Ok((results, conn)),
Err(e) => {
eprintln!("Got postgres error on query: {}", e);
Err(((), conn))
}
}
})
}
Err(e) => {
eprintln!("Got postgres error on prepare: {}", e);
Err((), conn)
}
}
})
}))?;
println!("My results are {:?}", results);
Ok(())
}from bb8.
khuey
commented on May 31, 2024
https://github.com/khuey/bb8/blob/master/postgres/examples/static_select.rs has a working example without async/await, btw, if you haven't seen that.
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Texlo-Dev
commented on May 31, 2024
A brief question:
On the error handling for the first prepare statement, why do you return an Err((), conn)? Won't Rust be expecting a Then with the result of the prepare?
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Texlo-Dev
commented on May 31, 2024
Yeah...it seems like using this library with async/await is going to be much more difficult than I had anticipated.
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khuey
commented on May 31, 2024
The basic premise of a the run function in bb8 is that you "check out" a connection from a pool, do some stuff with it, and return it when you're done. You can see the type signature of run https://github.com/khuey/bb8/blob/36b635b4741f36af2907fd32fe91b281ca0a2b93/src/lib.rs#L721. run takes a closure that returns something that implements IntoFuture<Item = (T, M::Connection), Error = (E, M::Connection)>.
In old style futures Result<T, E> implements IntoFuture<Item = T, Error = E> so you'll see that a lot. Operations that can fail but happen synchronously take advantage of this: and_then and then combinator closures often produce a Result instead of a "real" future.
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Texlo-Dev
commented on May 31, 2024
@khuey One thing I don't understand.
What is the Either enum that you are using and how do I get it?
It doesn't seem to be part of the futures package.
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Texlo-Dev
commented on May 31, 2024
I don't believe that the PostgreSQL example provided even compiles correctly though. :(
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khuey
commented on May 31, 2024
Either comes from https://docs.rs/futures/0.1.25/futures/future/enum.Either.html
If you check out this repository and cargo build --all --examples that fails?
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Texlo-Dev
commented on May 31, 2024
It doesn't fail, just thought I saw some syntax errors there. I guess not.
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Texlo-Dev
commented on May 31, 2024
However, I noticed that the futures crate does clash with the futures-preview crate I have installed. Do you know a way to have both installed under different names?
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