Merge branch 'main' into fix-tracing-channel-has-subscribers

The `TracingChannel` class in `node:diagnostics_channel` was missing the
`hasSubscribers` getter, causing it to return `undefined` instead of a
boolean. This adds the getter which returns `true` if any of the five
sub-channels (start, end, asyncStart, asyncEnd, error) have subscribers,
matching Node.js behavior.

Closes #27805

src/js/node/diagnostics_channel.ts

@@ -255,6 +255,16 @@ class TracingChannel {
   asyncEnd;
   error;
 
+  get hasSubscribers() {
+    return (
+      this.start.hasSubscribers ||
+      this.end.hasSubscribers ||
+      this.asyncStart.hasSubscribers ||
+      this.asyncEnd.hasSubscribers ||
+      this.error.hasSubscribers
+    );
+  }
+
   constructor(nameOrChannels) {
     if (typeof nameOrChannels === "string") {
       this.start = channel(`tracing:${nameOrChannels}:start`);

test/js/node/test/parallel/test-diagnostics-channel-tracing-channel-has-subscribers.js

@@ -0,0 +1,51 @@
+'use strict';
+
+const common = require('../common');
+const dc = require('diagnostics_channel');
+const assert = require('assert');
+
+const handler = common.mustNotCall();
+
+{
+  const handlers = {
+    start: common.mustNotCall()
+  };
+
+  const channel = dc.tracingChannel('test');
+
+  assert.strictEqual(channel.hasSubscribers, false);
+
+  channel.subscribe(handlers);
+  assert.strictEqual(channel.hasSubscribers, true);
+
+  channel.unsubscribe(handlers);
+  assert.strictEqual(channel.hasSubscribers, false);
+
+  channel.start.subscribe(handler);
+  assert.strictEqual(channel.hasSubscribers, true);
+
+  channel.start.unsubscribe(handler);
+  assert.strictEqual(channel.hasSubscribers, false);
+}
+
+{
+  const handlers = {
+    asyncEnd: common.mustNotCall()
+  };
+
+  const channel = dc.tracingChannel('test');
+
+  assert.strictEqual(channel.hasSubscribers, false);
+
+  channel.subscribe(handlers);
+  assert.strictEqual(channel.hasSubscribers, true);
+
+  channel.unsubscribe(handlers);
+  assert.strictEqual(channel.hasSubscribers, false);
+
+  channel.asyncEnd.subscribe(handler);
+  assert.strictEqual(channel.hasSubscribers, true);
+
+  channel.asyncEnd.unsubscribe(handler);
+  assert.strictEqual(channel.hasSubscribers, false);
+}