Fix TypeError when editing queued job with invalid JSON payload (#468)

When invalid JSON is submitted via the data edit form, the
JsonableBehavior threw a TypeError because json_decode returned null
but the return type was array.

Changes:
- Update _fromJson() to throw InvalidArgumentException with a
  descriptive error message instead of TypeError
- Catch the exception in data() action and show a flash error
- Preserve the user's invalid input so they can fix it
- Add data_string virtual property annotation to QueuedJob entity
- Add test for invalid JSON handling
- Fix PHPStan errors: handle nullable description() in example tasks

Author: dereuromark

src/Controller/Admin/QueuedJobsController.php

@@ -8,6 +8,7 @@
 use Cake\Http\Exception\NotFoundException;
 use Cake\I18n\DateTime;
 use Cake\View\JsonView;
+use InvalidArgumentException;
 use Queue\Queue\TaskFinder;
 use RuntimeException;
 
@@ -304,14 +305,21 @@ public function data(?int $id = null) {
 		}
 
 		if ($this->request->is(['patch', 'post', 'put'])) {
-			$queuedJob = $this->QueuedJobs->patchEntity($queuedJob, $this->request->getData());
-			if ($this->QueuedJobs->save($queuedJob)) {
-				$this->Flash->success(__d('queue', 'The queued job has been saved.'));
+			try {
+				$queuedJob = $this->QueuedJobs->patchEntity($queuedJob, $this->request->getData());
+				if ($this->QueuedJobs->save($queuedJob)) {
+					$this->Flash->success(__d('queue', 'The queued job has been saved.'));
 
-				return $this->redirect(['action' => 'view', $id]);
-			}
+					return $this->redirect(['action' => 'view', $id]);
+				}
 
-			$this->Flash->error(__d('queue', 'The queued job could not be saved. Please try again.'));
+				$this->Flash->error(__d('queue', 'The queued job could not be saved. Please try again.'));
+			} catch (InvalidArgumentException $e) {
+				$this->Flash->error($e->getMessage());
+
+				// Preserve the user's invalid input so they can fix it
+				$queuedJob->data_string = $this->request->getData('data_string');
+			}
 		}
 
 		$this->set(compact('queuedJob'));

src/Model/Behavior/JsonableBehavior.php

@@ -216,10 +216,15 @@ public function _decode($val) {
 	/**
 	 * @param string $val
 	 *
+	 * @throws \InvalidArgumentException
+	 *
 	 * @return array
 	 */
 	protected function _fromJson(string $val): array {
-		$json = json_decode($val, true, JSON_THROW_ON_ERROR);
+		$json = json_decode($val, true);
+		if (!is_array($json)) {
+			throw new InvalidArgumentException('Invalid JSON: ' . json_last_error_msg());
+		}
 
 		return $json;
 	}

src/Model/Entity/QueuedJob.php

@@ -9,6 +9,7 @@
  * @property int $id
  * @property string $job_task
  * @property array|null $data
+ * @property string|null $data_string Virtual property from JsonableBehavior
  * @property string|null $job_group
  * @property string|null $reference
  * @property \Cake\I18n\DateTime $created

tests/TestCase/Controller/Admin/QueuedJobsControllerTest.php

@@ -133,6 +133,27 @@ public function testDataPost() {
 		$this->assertSame($expected, $job->data);
 	}
 
+	/**
+	 * @return void
+	 */
+	public function testDataPostInvalidJson(): void {
+		$job = $this->createJob(['data' => '{"valid":"json"}']);
+
+		$this->enableRetainFlashMessages();
+		$data = [
+			'data_string' => 'not valid json {',
+		];
+		$this->post(['prefix' => 'Admin', 'plugin' => 'Queue', 'controller' => 'QueuedJobs', 'action' => 'data', $job->id], $data);
+
+		$this->assertResponseCode(200);
+		$this->assertFlashMessage('Invalid JSON: Syntax error');
+
+		// Verify original data was not modified
+		/** @var \Queue\Model\Entity\QueuedJob $job */
+		$job = $this->fetchTable('Queue.QueuedJobs')->get($job->id);
+		$this->assertSame('{"valid":"json"}', $job->data);
+	}
+
 	/**
 	 * Test index method
 	 *