Update

vendor/tailscale.com/util/eventbus/publish.go

@@ -0,0 +1,74 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package eventbus
+
+import (
+	"reflect"
+)
+
+// publisher is a uniformly typed wrapper around Publisher[T], so that
+// debugging facilities can look at active publishers.
+type publisher interface {
+	publishType() reflect.Type
+	Close()
+}
+
+// A Publisher publishes typed events on a bus.
+type Publisher[T any] struct {
+	client *Client
+	stop   stopFlag
+}
+
+func newPublisher[T any](c *Client) *Publisher[T] {
+	return &Publisher[T]{client: c}
+}
+
+// Close closes the publisher.
+//
+// Calls to Publish after Close silently do nothing.
+//
+// If the Bus or Client from which the Publisher was created is closed,
+// the Publisher is implicitly closed and does not need to be closed
+// separately.
+func (p *Publisher[T]) Close() {
+	// Just unblocks any active calls to Publish, no other
+	// synchronization needed.
+	p.stop.Stop()
+	p.client.deletePublisher(p)
+}
+
+func (p *Publisher[T]) publishType() reflect.Type {
+	return reflect.TypeFor[T]()
+}
+
+// Publish publishes event v on the bus.
+func (p *Publisher[T]) Publish(v T) {
+	// Check for just a stopped publisher or bus before trying to
+	// write, so that once closed Publish consistently does nothing.
+	select {
+	case <-p.stop.Done():
+		return
+	default:
+	}
+
+	evt := PublishedEvent{
+		Event: v,
+		From:  p.client,
+	}
+
+	select {
+	case p.client.publish() <- evt:
+	case <-p.stop.Done():
+	}
+}
+
+// ShouldPublish reports whether anyone is subscribed to the events
+// that this publisher emits.
+//
+// ShouldPublish can be used to skip expensive event construction if
+// nobody seems to care. Publishers must not assume that someone will
+// definitely receive an event if ShouldPublish returns true.
+func (p *Publisher[T]) ShouldPublish() bool {
+	return p.client.shouldPublish(reflect.TypeFor[T]())
+}