Copy the broadcaster auth state directly

Instead of re-registering the central channels on the tenant broadcaster one by one, copy the properties directly. Also the authenticated user callback wasn't copied before, so user authentication (/broadcasting/user-auth) that worked in central context would 403 in tenant context if the callback was registered in central context.

Author: lukinovec

src/Bootstrappers/BroadcastingConfigBootstrapper.php

@@ -91,27 +91,11 @@ public function bootstrap(Tenant $tenant): void
         // contract gets the same tenant broadcaster that the manager uses, instead of the stale central one.
         // The closure runs immediately (the extended singleton is already resolved), and it's also what makes
         // channel auth work in tenant context -- the broadcaster resolved here gets cached as the tenant
-        // manager's default driver and receives the central channel auth closures (see below).
+        // manager's default driver and receives the central broadcaster's auth state (see copyAuthState()).
         $this->app->extend(BroadcasterContract::class, function (BroadcasterContract $centralBroadcaster) {
             $tenantBroadcaster = $this->app->make(BroadcastManager::class)->connection();
 
-            // The newly resolved broadcaster doesn't have any channel auth closures registered, so the
-            // closures registered in central context (e.g. in routes/channels.php) have to be passed to it
-            // manually, otherwise, Broadcast::auth() would throw a 403 for those channels.
-            // Since Laravel only ever uses the default broadcaster's channel auth closures for broadcasting auth,
-            // we only have to pass the channel closures to the default broadcaster.
-            //
-            // The channel() and getChannels() methods aren't part of the Broadcaster contract -- they come
-            // from the abstract Broadcaster class, so the closures can only be copied between broadcasters extending it
-            // (which all of Laravel's default broadcasters, e.g. PusherBroadcaster, do).
-            if ($centralBroadcaster instanceof Broadcaster && $tenantBroadcaster instanceof Broadcaster) {
-                // invade() because the channel options can't be retrieved through any of the broadcaster's public methods
-                $channelOptions = invade($centralBroadcaster)->channelOptions;
-
-                foreach ($centralBroadcaster->getChannels() as $channel => $callback) {
-                    $tenantBroadcaster->channel($channel, $callback, $channelOptions[$channel] ?? []);
-                }
-            }
+            $this->copyAuthState($centralBroadcaster, $tenantBroadcaster);
 
             return $tenantBroadcaster;
         });
@@ -122,6 +106,32 @@ public function bootstrap(Tenant $tenant): void
         Broadcast::clearResolvedInstance();
     }
 
+    /**
+     * Copy the auth state (the channel auth closures, their options, and the authenticated user
+     * callback) from one broadcaster to another. A freshly resolved broadcaster has no auth state,
+     * so without the copying, channel auth and user auth would stop working (403) in tenant context.
+     *
+     * The auth state is stored on the abstract Broadcaster class, not in the Broadcaster
+     * contract, and it's stored in protected properties. Because of that, we have
+     * to check that both broadcasters are instances of the abstract Broadcaster class and
+     * use invade() to access the protected properties (for the $channels property, there
+     * is a public accessor -- getChannels() -- but since invade is already used here,
+     * we access the property directly for consistency).
+     */
+    protected function copyAuthState(BroadcasterContract $from, BroadcasterContract $to): void
+    {
+        if (! $from instanceof Broadcaster || ! $to instanceof Broadcaster) {
+            return;
+        }
+
+        $fromState = invade($from);
+        $toState = invade($to);
+
+        $toState->channels = $fromState->channels;
+        $toState->channelOptions = $fromState->channelOptions;
+        $toState->authenticatedUserCallback = $fromState->authenticatedUserCallback;
+    }
+
     public function revert(): void
     {
         // Revert the bound BroadcastManager and Broadcaster singletons back to their original state