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Updating the async API client example
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Added some code to show how you can run blocking Rust code inside a
foreign task queue.
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bendk committed Mar 19, 2024
1 parent 6ddd8cd commit e6c7523
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Showing 8 changed files with 305 additions and 132 deletions.
76 changes: 76 additions & 0 deletions examples/async-api-client/src/api_client.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,76 @@
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */

use crate::{run_task, ApiError, Result, TaskRunner};
use std::sync::Arc;

#[async_trait::async_trait]
pub trait HttpClient: Send + Sync {
async fn fetch(&self, url: String, credentials: String) -> Result<String>;
}

impl From<serde_json::Error> for ApiError {
fn from(e: serde_json::Error) -> Self {
Self::Json {
reason: e.to_string(),
}
}
}

#[derive(Debug, serde::Deserialize)]
pub struct Issue {
pub url: String,
pub title: String,
pub state: IssueState,
}

#[derive(Debug, serde::Deserialize)]
pub enum IssueState {
#[serde(rename = "open")]
Open,
#[serde(rename = "closed")]
Closed,
}

pub struct ApiClient {
http_client: Arc<dyn HttpClient>,
task_runner: Arc<dyn TaskRunner>,
}

impl ApiClient {
// Pretend this is a blocking call that needs to load the credentials from disk/network
fn load_credentials_sync(&self) -> String {
String::from("username:password")
}

async fn load_credentials(self: Arc<Self>) -> String {
let self_cloned = Arc::clone(&self);
run_task(&self.task_runner, move || {
self_cloned.load_credentials_sync()
})
.await
}
}

impl ApiClient {
pub fn new(http_client: Arc<dyn HttpClient>, task_runner: Arc<dyn TaskRunner>) -> Self {
Self {
http_client,
task_runner,
}
}

pub async fn get_issue(
self: Arc<Self>,
owner: String,
repository: String,
issue_number: u32,
) -> Result<Issue> {
let credentials = self.clone().load_credentials().await;
let url =
format!("https://api.github.com/repos/{owner}/{repository}/issues/{issue_number}");
let body = self.http_client.fetch(url, credentials).await?;
Ok(serde_json::from_str(&body)?)
}
}
17 changes: 15 additions & 2 deletions examples/async-api-client/src/async-api-client.udl
Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,20 @@ interface ApiError {
[Trait, WithForeign]
interface HttpClient {
[Throws=ApiError, Async]
string fetch(string url); // fetch an URL and return the body
string fetch(string url, string credentials); // fetch an URL and return the body
};

// Run Rust tasks in a thread pool.
// Implemented by the foreign bindings
[Trait, WithForeign]
interface TaskRunner {
[Async]
void run_task(RustTask task);
};

[Trait]
interface RustTask {
void execute();
};

dictionary Issue {
Expand All @@ -29,7 +42,7 @@ enum IssueState {

// Implemented by the Rust code
interface ApiClient {
constructor(HttpClient http_client);
constructor(HttpClient http_client, TaskRunner task_runner);

[Throws=ApiError, Async]
Issue get_issue(string owner, string repository, u32 issue_number);
Expand Down
131 changes: 7 additions & 124 deletions examples/async-api-client/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,13 @@
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */

use std::sync::Arc;
mod api_client;
mod tasks;
mod test_data;

pub use api_client::{ApiClient, HttpClient, Issue, IssueState};
pub use tasks::{run_task, RustTask, TaskRunner};
pub use test_data::test_response_data;

#[derive(Debug, thiserror::Error)]
pub enum ApiError {
Expand All @@ -16,127 +22,4 @@ pub enum ApiError {

pub type Result<T> = std::result::Result<T, ApiError>;

#[async_trait::async_trait]
pub trait HttpClient: Send + Sync {
async fn fetch(&self, url: String) -> Result<String>;
}

#[derive(Debug, serde::Deserialize)]
pub struct Issue {
url: String,
title: String,
state: IssueState,
}

#[derive(Debug, serde::Deserialize)]
pub enum IssueState {
#[serde(rename = "open")]
Open,
#[serde(rename = "closed")]
Closed,
}

pub struct ApiClient {
http_client: Arc<dyn HttpClient>,
}

impl ApiClient {
pub fn new(http_client: Arc<dyn HttpClient>) -> Self {
Self { http_client }
}

pub async fn get_issue(
&self,
owner: String,
repository: String,
issue_number: u32,
) -> Result<Issue> {
let url =
format!("https://api.github.com/repos/{owner}/{repository}/issues/{issue_number}");
let body = self.http_client.fetch(url).await?;
Ok(serde_json::from_str(&body)?)
}
}

impl From<serde_json::Error> for ApiError {
fn from(e: serde_json::Error) -> Self {
Self::Json {
reason: e.to_string(),
}
}
}

/// Sample data downloaded from a real github api call
///
/// The tests don't make real HTTP calls to avoid them failing because of network errors.
pub fn test_response_data() -> String {
String::from(
r#"{
"url": "https://api.github.com/repos/mozilla/uniffi-rs/issues/2017",
"repository_url": "https://api.github.com/repos/mozilla/uniffi-rs",
"labels_url": "https://api.github.com/repos/mozilla/uniffi-rs/issues/2017/labels{/name}",
"comments_url": "https://api.github.com/repos/mozilla/uniffi-rs/issues/2017/comments",
"events_url": "https://api.github.com/repos/mozilla/uniffi-rs/issues/2017/events",
"html_url": "https://github.com/mozilla/uniffi-rs/issues/2017",
"id": 2174982360,
"node_id": "I_kwDOECpYAM6Bo5jY",
"number": 2017,
"title": "Foreign-implemented async traits",
"user": {
"login": "bendk",
"id": 1012809,
"node_id": "MDQ6VXNlcjEwMTI4MDk=",
"avatar_url": "https://avatars.githubusercontent.com/u/1012809?v=4",
"gravatar_id": "",
"url": "https://api.github.com/users/bendk",
"html_url": "https://github.com/bendk",
"followers_url": "https://api.github.com/users/bendk/followers",
"following_url": "https://api.github.com/users/bendk/following{/other_user}",
"gists_url": "https://api.github.com/users/bendk/gists{/gist_id}",
"starred_url": "https://api.github.com/users/bendk/starred{/owner}{/repo}",
"subscriptions_url": "https://api.github.com/users/bendk/subscriptions",
"organizations_url": "https://api.github.com/users/bendk/orgs",
"repos_url": "https://api.github.com/users/bendk/repos",
"events_url": "https://api.github.com/users/bendk/events{/privacy}",
"received_events_url": "https://api.github.com/users/bendk/received_events",
"type": "User",
"site_admin": false
},
"labels": [
],
"state": "open",
"locked": false,
"assignee": null,
"assignees": [
],
"milestone": null,
"comments": 0,
"created_at": "2024-03-07T23:07:29Z",
"updated_at": "2024-03-07T23:07:29Z",
"closed_at": null,
"author_association": "CONTRIBUTOR",
"active_lock_reason": null,
"body": "We currently allow Rust code to implement async trait methods, but foreign implementations are not supported. We should extend support to allow for foreign code.\\r\\n\\r\\nI think this is a key feature for full async support. It allows Rust code to define an async method that depends on a foreign async method. This allows users to use async code without running a Rust async runtime, you can effectively piggyback on the foreign async runtime.",
"closed_by": null,
"reactions": {
"url": "https://api.github.com/repos/mozilla/uniffi-rs/issues/2017/reactions",
"total_count": 0,
"+1": 0,
"-1": 0,
"laugh": 0,
"hooray": 0,
"confused": 0,
"heart": 0,
"rocket": 0,
"eyes": 0
},
"timeline_url": "https://api.github.com/repos/mozilla/uniffi-rs/issues/2017/timeline",
"performed_via_github_app": null,
"state_reason": null
}"#,
)
}

uniffi::include_scaffolding!("async-api-client");
90 changes: 90 additions & 0 deletions examples/async-api-client/src/tasks.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,90 @@
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */

use std::sync::{Arc, Mutex};

#[async_trait::async_trait]
pub trait TaskRunner: Send + Sync {
async fn run_task(&self, task: Arc<dyn RustTask>);
}

pub trait RustTask: Send + Sync {
fn execute(&self);
}

pub async fn run_task<F, T>(runner: &Arc<dyn TaskRunner>, closure: F) -> T
where
F: FnOnce() -> T + Send + Sync + 'static,
T: Send + 'static,
{
let closure = Arc::new(TaskClosure::new(closure));
runner
.run_task(Arc::clone(&closure) as Arc<dyn RustTask>)
.await;
closure.into_result()
}

struct TaskClosure<F, T>
where
F: FnOnce() -> T + Send + Sync,
T: Send,
{
inner: Mutex<TaskClosureInner<F, T>>,
}

enum TaskClosureInner<F, T>
where
F: FnOnce() -> T + Send + Sync,
T: Send,
{
Pending(F),
Running,
Complete(T),
Finished,
}

impl<F, T> TaskClosure<F, T>
where
F: FnOnce() -> T + Send + Sync,
T: Send,
{
fn new(closure: F) -> Self {
Self {
inner: Mutex::new(TaskClosureInner::Pending(closure)),
}
}

fn into_result(&self) -> T {
let mut inner = self.inner.lock().unwrap();
match *inner {
TaskClosureInner::Pending(_) => panic!("Task never ran"),
TaskClosureInner::Running => panic!("Task still running"),
TaskClosureInner::Finished => panic!("Task already finished"),
TaskClosureInner::Complete(_) => (),
};
match std::mem::replace(&mut *inner, TaskClosureInner::Finished) {
TaskClosureInner::Complete(v) => v,
_ => unreachable!(),
}
}
}

impl<F, T> RustTask for TaskClosure<F, T>
where
F: FnOnce() -> T + Send + Sync,
T: Send,
{
fn execute(&self) {
let mut inner = self.inner.lock().unwrap();
match std::mem::replace(&mut *inner, TaskClosureInner::Running) {
TaskClosureInner::Pending(f) => {
let result = f();
*inner = TaskClosureInner::Complete(result)
}
TaskClosureInner::Running => panic!("Task already started"),
TaskClosureInner::Complete(_) => panic!("Task already executed"),
TaskClosureInner::Finished => panic!("Task already finished"),
}
}
}
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