From 0a46e017b86216119cb2d8f86254132f898c9e9a Mon Sep 17 00:00:00 2001
From: Joe Neeman <joeneeman@gmail.com>
Date: Wed, 22 Feb 2023 13:12:29 -0600
Subject: [PATCH] Make wasm requests cancel when the future drops.

---
 Cargo.toml           |  2 ++
 src/wasm/client.rs   |  7 +++++--
 src/wasm/mod.rs      | 26 ++++++++++++++++++++++++++
 src/wasm/response.rs | 10 +++++++++-
 4 files changed, 42 insertions(+), 3 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index 1102d4e87..6dd3f1639 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -159,6 +159,8 @@ wasm-streams = { version = "0.2", optional = true }
 [target.'cfg(target_arch = "wasm32")'.dependencies.web-sys]
 version = "0.3.25"
 features = [
+    "AbortController",
+    "AbortSignal",
     "Headers",
     "Request",
     "RequestInit",
diff --git a/src/wasm/client.rs b/src/wasm/client.rs
index 56849db77..cfe97bf03 100644
--- a/src/wasm/client.rs
+++ b/src/wasm/client.rs
@@ -4,7 +4,7 @@ use std::{fmt, future::Future, sync::Arc};
 use url::Url;
 use wasm_bindgen::prelude::{wasm_bindgen, UnwrapThrowExt as _};
 
-use super::{Request, RequestBuilder, Response};
+use super::{AbortGuard, Request, RequestBuilder, Response};
 use crate::IntoUrl;
 
 #[wasm_bindgen]
@@ -216,6 +216,9 @@ async fn fetch(req: Request) -> crate::Result<Response> {
         }
     }
 
+    let abort = AbortGuard::new()?;
+    init.signal(Some(&abort.signal()));
+
     let js_req = web_sys::Request::new_with_str_and_init(req.url().as_str(), &init)
         .map_err(crate::error::wasm)
         .map_err(crate::error::builder)?;
@@ -247,7 +250,7 @@ async fn fetch(req: Request) -> crate::Result<Response> {
     }
 
     resp.body(js_resp)
-        .map(|resp| Response::new(resp, url))
+        .map(|resp| Response::new(resp, url, abort))
         .map_err(crate::error::request)
 }
 
diff --git a/src/wasm/mod.rs b/src/wasm/mod.rs
index 249b4a284..e99fb11fb 100644
--- a/src/wasm/mod.rs
+++ b/src/wasm/mod.rs
@@ -1,4 +1,5 @@
 use wasm_bindgen::JsCast;
+use web_sys::{AbortController, AbortSignal};
 
 mod body;
 mod client;
@@ -25,3 +26,28 @@ where
         .dyn_into::<T>()
         .map_err(|_js_val| "promise resolved to unexpected type".into())
 }
+
+/// A guard that cancels a fetch request when dropped.
+struct AbortGuard {
+    ctrl: AbortController,
+}
+
+impl AbortGuard {
+    fn new() -> crate::Result<Self> {
+        Ok(AbortGuard {
+            ctrl: AbortController::new()
+                .map_err(crate::error::wasm)
+                .map_err(crate::error::builder)?,
+        })
+    }
+
+    fn signal(&self) -> AbortSignal {
+        self.ctrl.signal()
+    }
+}
+
+impl Drop for AbortGuard {
+    fn drop(&mut self) {
+        self.ctrl.abort();
+    }
+}
diff --git a/src/wasm/response.rs b/src/wasm/response.rs
index 83c7a98c1..9b98da4f3 100644
--- a/src/wasm/response.rs
+++ b/src/wasm/response.rs
@@ -5,6 +5,8 @@ use http::{HeaderMap, StatusCode};
 use js_sys::Uint8Array;
 use url::Url;
 
+use crate::wasm::AbortGuard;
+
 #[cfg(feature = "stream")]
 use wasm_bindgen::JsCast;
 
@@ -17,16 +19,22 @@ use serde::de::DeserializeOwned;
 /// A Response to a submitted `Request`.
 pub struct Response {
     http: http::Response<web_sys::Response>,
+    _abort: AbortGuard,
     // Boxed to save space (11 words to 1 word), and it's not accessed
     // frequently internally.
     url: Box<Url>,
 }
 
 impl Response {
-    pub(super) fn new(res: http::Response<web_sys::Response>, url: Url) -> Response {
+    pub(super) fn new(
+        res: http::Response<web_sys::Response>,
+        url: Url,
+        abort: AbortGuard,
+    ) -> Response {
         Response {
             http: res,
             url: Box::new(url),
+            _abort: abort,
         }
     }