fix: avoid unhandled rejection when signal is already aborted

package.json

@@ -28,6 +28,7 @@
     "@types/chai": "^4.3.5",
     "@types/chai-as-promised": "^7.1.5",
     "@types/mocha": "^10.0.1",
+    "@types/node": "^22.10.1",
     "@typescript-eslint/eslint-plugin": "^7.6.0",
     "@typescript-eslint/parser": "^7.6.0",
     "chai": "^4.3.7",

src/index.ts

@@ -9,10 +9,6 @@ export function abortable<T>(
 ): Promise<T> {
   if (!signal) return promise
   return new Promise<T>((resolve, reject) => {
-    if (signal.aborted) {
-      reject(newAbortError())
-      return
-    }
     const cleanup = () => {
       const callbacks = { resolve, reject }
       // Prevent memory leaks.  If the input promise never resolves, then the handlers
@@ -33,5 +29,9 @@ export function abortable<T>(
       (value) => cleanup().resolve(value),
       (error) => cleanup().reject(error)
     )
+    if (signal.aborted) {
+      reject(newAbortError())
+      return
+    }
   })
 }

test/abortable.test.ts

@@ -33,6 +33,18 @@ describe(`abortable`, function () {
       p.resolve(42),
     ])
   })
+  it(`bug - unhandled rejection when signal is aborted`, async function () {
+    const p = withResolvers<number>()
+    const ac = new AbortController()
+    ac.abort()
+    const [, error] = tried(() => ac.signal.throwIfAborted())()
+    p.reject(new Error('test'))
+    await Promise.all([
+      expect(abortable(p.promise, ac.signal))
+        .to.be.rejectedWith(DOMException)
+        .that.eventually.deep.equals(error),
+    ])
+  })
   it(`rejects if signal aborts before promise resolves`, async function () {
     const p = withResolvers<number>()
     const ac = new AbortController()

test/configure.ts

@@ -1,3 +1,7 @@
 import chai from 'chai'
 import chaiAsPromised from 'chai-as-promised'
 chai.use(chaiAsPromised)
+
+process.on('unhandledRejection', () => {
+  throw new Error('unhandled rejection!')
+})