feat(PubSub): Add OptimisticSubscribe sample (#2100)

Author: cy-yun

pubsub/api/src/optimistic_subscribe.php

@@ -0,0 +1,66 @@
+<?php
+
+/**
+ * Copyright 2025 Google LLC.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * For instructions on how to run the full sample:
+ *
+ * @see https://github.com/GoogleCloudPlatform/php-docs-samples/blob/main/pubsub/api/README.md
+ */
+
+namespace Google\Cloud\Samples\PubSub;
+
+# [START pubsub_optimistic_subscribe]
+use Google\Cloud\Core\Exception\NotFoundException;
+use Google\Cloud\PubSub\PubSubClient;
+
+/**
+ * Optimistically subscribes to a topic
+ *
+ * @param string $projectId  The Google project ID.
+ * @param string $topicName  The Pub/Sub topic name.
+ * @param string $subscriptionId  The ID of the subscription.
+ */
+function optimistic_subscribe(
+    string $projectId,
+    string $topicName,
+    string $subscriptionId
+): void {
+
+    $pubsub = new PubSubClient([
+        'projectId' => $projectId,
+    ]);
+
+    $subscription = $pubsub->subscription($subscriptionId);
+
+    try {
+        $messages = $subscription->pull();
+        foreach ($messages as $message) {
+            printf('PubSub Message: %s' . PHP_EOL, $message->data());
+            $subscription->acknowledge($message);
+        }
+    } catch (NotFoundException $e) { // Subscription is not found
+        printf('Exception Message: %s' . PHP_EOL, $e->getMessage());
+        printf('StackTrace: %s' . PHP_EOL, $e->getTraceAsString());
+        // Create subscription and retry the pull. Any messages published before subscription creation would not be received.
+        $pubsub->subscribe($subscriptionId, $topicName);
+        optimistic_subscribe($projectId, $topicName, $subscriptionId);
+    }
+}
+# [END pubsub_optimistic_subscribe]
+require_once __DIR__ . '/../../../testing/sample_helpers.php';
+\Google\Cloud\Samples\execute_sample(__FILE__, __NAMESPACE__, $argv);

pubsub/api/test/pubsubTest.php

@@ -562,4 +562,42 @@ public function testSubscriberErrorListener()
         $this->assertMatchesRegularExpression('/Exception Message/', $output);
         $this->assertMatchesRegularExpression(sprintf('/Resource not found \(resource=%s\)/', $subscription), $output);
     }
+
+    public function testOptimisticSubscribe()
+    {
+        $topic = $this->requireEnv('GOOGLE_PUBSUB_TOPIC');
+        $subcriptionId = 'test-subscription-' . rand();
+
+        $output = $this->runFunctionSnippet('optimistic_subscribe', [
+            self::$projectId,
+            $topic,
+            $subcriptionId
+        ]);
+        $this->assertMatchesRegularExpression('/Exception Message/', $output);
+        $this->assertMatchesRegularExpression(sprintf('/Resource not found \(resource=%s\)/',  $subcriptionId), $output);
+
+        $testMessage = 'This is a test message';
+        $output = $this->runFunctionSnippet('publish_message', [
+            self::$projectId,
+            $topic,
+            $testMessage,
+        ]);
+        $this->assertMatchesRegularExpression('/Message published/', $output);
+        $output = $this->runFunctionSnippet('optimistic_subscribe', [
+            self::$projectId,
+            $topic,
+            $subcriptionId
+        ]);
+        $this->assertMatchesRegularExpression(sprintf('/PubSub Message: %s/', $testMessage), $output);
+        $this->assertDoesNotMatchRegularExpression('/Exception Message/', $output);
+        $this->assertDoesNotMatchRegularExpression(sprintf('/Resource not found \(resource=%s\)/', $subcriptionId), $output);
+
+        // Delete subscription
+        $output = $this->runFunctionSnippet('delete_subscription', [
+            self::$projectId,
+            $subcriptionId,
+        ]);
+        $this->assertMatchesRegularExpression('/Subscription deleted:/', $output);
+        $this->assertMatchesRegularExpression(sprintf('/%s/', $subcriptionId), $output);
+    }
 }