FIX unhandled rejections (#1384)

* FIX unhandled rejections

* ADD changelog

* FIX lint

Author: pubkey

.github/README.md

@@ -257,6 +257,8 @@ const elector = createLeaderElection(channel);
 await elector.die();
 ```
 
+**NOTICE:** When the leader dies, its calls to `awaitLeadership()` will no longer resolve.
+
 ### Handle duplicate leaders
 
 Duplicate leadership can happen on rare occurences like when the [CPU is on 100%](https://web.archive.org/web/20201221051328/https://github.com/pubkey/broadcast-channel/issues/385) for longer time, or the browser [has throttled the javascript timers](https://web.archive.org/web/20201221051312/https://github.com/pubkey/broadcast-channel/issues/414).

.github/workflows/main.yml

@@ -98,7 +98,7 @@ jobs:
     runs-on: ubuntu-22.04
     strategy:
       matrix:
-        node: ['18.18.2', '20.9.0']
+        node: ['22.22.0', '24.13.0']
     steps:
       - uses: actions/checkout@v6
       - name: Setup Node.js environment

CHANGELOG.md

@@ -3,6 +3,11 @@
 
 ## X.X.X (comming soon)
 
+## 7.3.0 (20 January 2026)
+
+- FIX `unhandledRejection` thrown when `leader.die()` is called while a call to `awaitLeadership()` is still running.
+
+
 ## 7.2.0 (27 October 2025)
 
 - fix(leader-election-web-lock): rethrow WebLocks acquisition errors to avoid stuck leader election [#1360](https://github.com/pubkey/broadcast-channel/pull/1360)

src/leader-election-web-lock.js

@@ -31,6 +31,7 @@ export const LeaderElectionWebLock = function (broadcastChannel, options) {
 };
 
 
+const LEADER_DIE_ABORT_SIGNAL_MESSAGE = 'LeaderElectionWebLock.die() called';
 
 LeaderElectionWebLock.prototype = {
     hasLeader() {
@@ -65,10 +66,19 @@ LeaderElectionWebLock.prototype = {
                         return returnPromise;
                     }
                 ).catch((err) => {
-                    if (this._wKMC.rej) {
-                        this._wKMC.rej(err);
+                    if (err.message && err.message === LEADER_DIE_ABORT_SIGNAL_MESSAGE) {
+                        /**
+                         * In this case we do nothing!
+                         * The leader died and awaitLeadership()
+                         * will never resolve. Also since this is not an error,
+                         * it will not throw.
+                         */
+                    } else {
+                        if (this._wKMC.rej) {
+                            this._wKMC.rej(err);
+                        }
+                        reject(err);
                     }
-                    reject(err);
                 });
             });
         }
@@ -90,8 +100,13 @@ LeaderElectionWebLock.prototype = {
         if (this._wKMC.res) {
             this._wKMC.res();
         }
+
+        /**
+         * We have to fire an abort signal
+         * so that the navigator.locks.request stops.
+         */
         if (this._wKMC.c) {
-            this._wKMC.c.abort(new Error('LeaderElectionWebLock.die() called'));
+            this._wKMC.c.abort(new Error(LEADER_DIE_ABORT_SIGNAL_MESSAGE));
         }
         return sendLeaderMessage(this, 'death');
     }

test/integration.test.js

@@ -18,6 +18,28 @@ if (isNode) {
         console.dir(origin);
         process.exit(1);
     });
+
+    /**
+     * In no case it should throw an unhandledRejection
+     */
+    process.on('unhandledRejection', async function (error, p) {
+        console.log('unhandledRejection');
+
+        // use log and error because some CI terminals do not show errors.
+        try {
+            console.dir(await p);
+        } catch (err) {
+            console.log('------- COULD NOT AWAIT p');
+            logUnknownError(err);
+            logUnknownError(error);
+            process.exit(5);
+        }
+        console.dir((error).stack);
+        console.error(error);
+        console.dir(error);
+        console.log('------- END OF unhandledRejection debug logs');
+        process.exit(5);
+    });
 }
 
 /**
@@ -797,3 +819,18 @@ if (isNode) {
 }
 
 useOptions.forEach(o => runTest(o));
+
+
+function logUnknownError(err) {
+    if (err instanceof Error) {
+        console.error(err.stack || err.message);
+    } else {
+        console.error('Non-Error rejection:', err);
+        console.error(err.stack || err.message);
+        try {
+            console.error(JSON.stringify(err, null, 2));
+        } catch (err2) {
+            console.error(String(err));
+        }
+    }
+}