Issue #3308828 by omkar.podey, phenaproxima: Handle the case where the marker...

Issue #3308828 by omkar.podey, phenaproxima: Handle the case where the marker file has been detected but can't be decoded

package_manager/src/FailureMarker.php

@@ -78,7 +78,12 @@ final class FailureMarker {
 
     if (file_exists($path)) {
       $data = file_get_contents($path);
-      $data = Json::decode($data);
+      try {
+        $data = json_decode($data, TRUE, 512, JSON_THROW_ON_ERROR);
+      }
+      catch (\JsonException $exception) {
+        throw new ApplyFailedException('Failure marker file exists but cannot be decoded.', $exception->getCode(), $exception);
+      }
 
       throw new ApplyFailedException($data['message']);
     }

package_manager/tests/src/Kernel/FailureMarkerTest.php

+<?php
+
+namespace Drupal\Tests\package_manager\Kernel;
+
+use Drupal\package_manager\Exception\ApplyFailedException;
+
+/**
+ * @coversDefaultClass \Drupal\package_manager\FailureMarker
+ *
+ * @group package_manager
+ */
+class FailureMarkerTest extends PackageManagerKernelTestBase {
+
+  /**
+   * @covers ::assertNotExists
+   */
+  public function testExceptionIfExists(): void {
+    $failure_marker = $this->container->get('package_manager.failure_marker');
+    $failure_marker->write($this->createStage(), 'Disastrous catastrophe!');
+
+    $this->expectException(ApplyFailedException::class);
+    $this->expectExceptionMessage('Disastrous catastrophe!');
+    $failure_marker->assertNotExists();
+  }
+
+  /**
+   * Tests that an exception is thrown if the marker file contains invalid JSON.
+   *
+   * @covers ::assertNotExists
+   */
+  public function testExceptionForInvalidJson(): void {
+    $failure_marker = $this->container->get('package_manager.failure_marker');
+    // Write the failure marker with invalid JSON.
+    file_put_contents($failure_marker->getPath(), '{}}');
+
+    $this->expectException(ApplyFailedException::class);
+    $this->expectExceptionMessage('Failure marker file exists but cannot be decoded.');
+    $failure_marker->assertNotExists();
+  }
+
+}