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Pass State in as a reference #3

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Pass State in as a reference #3

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51630b6
make deps more similar to combinator version
alsuren Jan 21, 2020
491cede
can't get the lifetimes right
alsuren Jan 21, 2020
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6 changes: 3 additions & 3 deletions examples/handlers/simple_async_handlers_await/Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -10,8 +10,8 @@ edition = "2018"
gotham = { path = "../../../gotham" }
gotham_derive = { path = "../../../gotham_derive" }

mime = "0.3.16"
mime = "0.3"
futures = "0.3.1"
serde = "1.0.104"
serde_derive = "1.0.104"
serde = "1.0"
serde_derive = "1.0"
tokio = "0.2.9"
29 changes: 8 additions & 21 deletions examples/handlers/simple_async_handlers_await/src/main.rs
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Expand Up @@ -4,9 +4,9 @@ use futures::prelude::*;
use std::pin::Pin;
use std::time::{Duration, Instant};

use gotham::hyper::{Body, StatusCode};
use gotham::hyper::{Body, Response, StatusCode};

use gotham::handler::HandlerResult;
use gotham::handler::{HandlerError, HandlerResult};
use gotham::helpers::http::response::create_response;
use gotham::router::builder::DefineSingleRoute;
use gotham::router::builder::{build_simple_router, DrawRoutes};
Expand Down Expand Up @@ -60,34 +60,21 @@ fn sleep(seconds: u64) -> SleepFuture {

/// This handler sleeps for the requested number of seconds, using the `sleep()`
/// helper method, above.
async fn sleep_handler(mut state: State) -> HandlerResult {
let seconds = QueryStringExtractor::take_from(&mut state).seconds;
async fn sleep_handler(state: &mut State) -> HandlerResult {
let seconds = QueryStringExtractor::take_from(state).seconds;
println!("sleep for {} seconds once: starting", seconds);
// Here, we call the sleep function and turn its old-style future into
// a new-style future. Note that this step doesn't block: it just sets
// up the timer so that we can use it later.
let sleep_future = sleep(seconds);

// Here is where the serious sleeping happens. We yield execution of
// this block until sleep_future is resolved.
// The Ok("slept for x seconds") value is stored in result.
let data = sleep_future.await;

// Here, we convert the result from `sleep()` into the form that Gotham
// expects: `state` is owned by this block so we need to return it.
// We also convert any errors that we have into the form that Hyper
// expects, using the helper from IntoHandlerError.
let res = create_response(&state, StatusCode::OK, mime::TEXT_PLAIN, data);
println!("sleep for {} seconds once: finished", seconds);
Ok((state, res))
Ok(res)
}

/// It calls sleep(1) as many times as needed to make the requested duration.
///
/// Notice how much easier it is to read than the version in
/// `simple_async_handlers`.
async fn loop_handler(mut state: State) -> HandlerResult {
let seconds = QueryStringExtractor::take_from(&mut state).seconds;
async fn loop_handler(state: &mut State) -> HandlerResult {
let seconds = QueryStringExtractor::take_from(state).seconds;
println!("sleep for one second {} times: starting", seconds);

// The code within this block reads exactly like syncronous code.
Expand All @@ -106,7 +93,7 @@ async fn loop_handler(mut state: State) -> HandlerResult {
Body::from(accumulator),
);
println!("sleep for one second {} times: finished", seconds);
Ok((state, res))
Ok(res)
}

/// Create a `Router`.
Expand Down
5 changes: 3 additions & 2 deletions gotham/src/handler/mod.rs
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Expand Up @@ -24,13 +24,14 @@ pub mod assets;
pub use self::error::{HandlerError, IntoHandlerError};

/// A type alias for the results returned by async fns that can be passed to to_async.
pub type HandlerResult = std::result::Result<(State, Response<Body>), (State, HandlerError)>;
pub type HandlerResult = std::result::Result<Response<Body>, HandlerError>;

/// A type alias for the trait objects returned by `HandlerService`.
///
/// When the `Future` resolves to an error, the `(State, HandlerError)` value is used to generate
/// an appropriate HTTP error response.
pub type HandlerFuture = dyn Future<Output = HandlerResult> + Send;
pub type HandlerFuture =
dyn Future<Output = std::result::Result<(State, Response<Body>), (State, HandlerError)>> + Send;

/// A `Handler` is an asynchronous function, taking a `State` value which represents the request
/// and related runtime state, and returns a future which resolves to a response.
Expand Down
25 changes: 18 additions & 7 deletions gotham/src/router/builder/single.rs
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Expand Up @@ -4,7 +4,7 @@ use std::panic::RefUnwindSafe;

use crate::extractor::{PathExtractor, QueryStringExtractor};
use crate::handler::assets::{DirHandler, FileHandler, FileOptions, FilePathExtractor};
use crate::handler::{Handler, HandlerResult, NewHandler};
use crate::handler::{Handler, HandlerFuture, HandlerResult, NewHandler};
use crate::pipeline::chain::PipelineHandleChain;
use crate::router::builder::{
ExtendRouteMatcher, ReplacePathExtractor, ReplaceQueryStringExtractor, SingleRouteBuilder,
Expand Down Expand Up @@ -127,9 +127,9 @@ pub trait DefineSingleRoute {
/// # use gotham::middleware::session::NewSessionMiddleware;
/// # use gotham::test::TestServer;
/// #
/// async fn my_handler(state: State) -> HandlerResult {
/// async fn my_handler(state: &mut State) -> HandlerResult {
/// // Handler implementation elided.
/// # Ok((state, Response::builder().status(StatusCode::ACCEPTED).body(Body::empty()).unwrap()))
/// # Ok(Response::builder().status(StatusCode::ACCEPTED).body(Body::empty()).unwrap())
/// }
/// #
/// # fn router() -> Router {
Expand All @@ -152,13 +152,24 @@ pub trait DefineSingleRoute {
/// # assert_eq!(response.status(), StatusCode::ACCEPTED);
/// # }
/// ```
fn to_async<H, Fut>(self, handler: H)
fn to_async<'s, H, Fut>(self, handler: H)
where
Self: Sized,
H: (FnOnce(State) -> Fut) + RefUnwindSafe + Copy + Send + Sync + 'static,
Fut: Future<Output = HandlerResult> + Send + 'static,
H: (FnOnce(&'_ mut State) -> Fut) + RefUnwindSafe + Copy + Send + Sync + 'static,
Fut: Future<Output = HandlerResult> + Send,
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@alsuren alsuren May 23, 2020 •
edited
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The problem is that you can't tie the lifetime of State to that of Fut, because it has no lifetime parameters, and therefore no way to specify the required higher-ranked lifetime bounds ( https://doc.rust-lang.org/reference/trait-bounds.html#higher-ranked-trait-bounds ). If I manage to work-around this issue then it should fix gotham-rs#431 . I am going to chase this up in the upstream rust repo here:
rust-lang/rust#45994

If we manage to fix this, I will also have a good solution to the ergonomics problems in tag1consulting/goose#22

There is a slightly more self-contained exploration of this issue here: https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=63830174a65ea4adf45eb5b095f0ae9b

{
self.to_new_handler(move || Ok(move |s: State| handler(s).boxed()))
self.to_new_handler(move || {
Ok(move |mut state: State| {
async move {
let res = { handler(&mut state).await };
match res {
Ok(r) => Ok((state, r)),
Err(e) => Err((state, e)),
}
}
.boxed()
})
})
}
/// Directs the route to the given `NewHandler`. This gives more control over how `Handler`
/// values are constructed.
Expand Down