From 7e1414efcfc29f9ff142efa5622f3f7b1234c819 Mon Sep 17 00:00:00 2001
From: Connor Peet <connor@peet.io>
Date: Fri, 8 Nov 2024 22:21:57 -0800
Subject: [PATCH] fix: propagate abort reason in derived signals Fixes #101

---
 src/common/Event.ts      |  8 ++++----
 src/common/abort.test.ts | 21 +++++++++++++++++++++
 src/common/abort.ts      |  4 ++--
 3 files changed, 27 insertions(+), 6 deletions(-)
 create mode 100644 src/common/abort.test.ts

diff --git a/src/common/Event.ts b/src/common/Event.ts
index 59dddb0..1f84c7e 100644
--- a/src/common/Event.ts
+++ b/src/common/Event.ts
@@ -79,10 +79,10 @@ export namespace Event {
 }
 
 /** Creates an Event that fires when the signal is aborted. */
-export const onAbort = (signal: AbortSignal): { event: Event<void> } & IDisposable => {
-  const evt = new OneShotEvent<void>();
+export const onAbort = (signal: AbortSignal): { event: Event<unknown> } & IDisposable => {
+  const evt = new OneShotEvent<unknown>();
   if (signal.aborted) {
-    evt.emit();
+    evt.emit(signal.reason);
     return { event: evt.addListener, dispose: () => {} };
   }
 
@@ -90,7 +90,7 @@ export const onAbort = (signal: AbortSignal): { event: Event<void> } & IDisposab
 
   // @types/node is currently missing the event types on AbortSignal
   const l = () => {
-    evt.emit();
+    evt.emit(signal.reason);
     dispose();
   };
 
diff --git a/src/common/abort.test.ts b/src/common/abort.test.ts
new file mode 100644
index 0000000..d8b5f78
--- /dev/null
+++ b/src/common/abort.test.ts
@@ -0,0 +1,21 @@
+import { expect } from 'chai';
+import { deriveAbortController } from './abort';
+
+describe('deriveAbortController', () => {
+  it('should return an aborted AbortController when the provided signal is already aborted', () => {
+    const parentCtrl = new AbortController();
+    parentCtrl.abort(new Error('asdf'));
+    const { ctrl } = deriveAbortController(parentCtrl.signal);
+    expect(ctrl.signal.aborted).to.be.true;
+    expect(ctrl.signal.reason).to.equal(parentCtrl.signal.reason);
+  });
+
+  it('should abort the new AbortController when the provided signal aborts', () => {
+    const parentCtrl = new AbortController();
+    const { ctrl } = deriveAbortController(parentCtrl.signal);
+    expect(ctrl.signal.aborted).to.be.false;
+    parentCtrl.abort(new Error('asdf'));
+    expect(ctrl.signal.aborted).to.be.true;
+    expect(ctrl.signal.reason).to.equal(parentCtrl.signal.reason);
+  });
+});
diff --git a/src/common/abort.ts b/src/common/abort.ts
index 264c319..9862997 100644
--- a/src/common/abort.ts
+++ b/src/common/abort.ts
@@ -22,10 +22,10 @@ export const deriveAbortController = (
   }
 
   if (signal.aborted) {
-    ctrl.abort();
+    ctrl.abort(signal.reason);
   } else {
     const abortEvt = onAbort(signal);
-    abortEvt.event(() => ctrl.abort());
+    abortEvt.event(reason => ctrl.abort(reason));
     dispose = abortEvt.dispose;
   }