Added automatic retry for empty app lists in GetAppList.

src/Resource/FetchAppListException.php

@@ -0,0 +1,12 @@
+<?php
+declare(strict_types=1);
+
+namespace ScriptFUSION\Porter\Provider\Steam\Resource;
+
+/**
+ * The exception that is thrown when a permanent error occurs trying to fetch the app list.
+ */
+final class FetchAppListException extends \RuntimeException
+{
+    // Intentionally empty.
+}

src/Resource/GetAppList.php

@@ -22,10 +22,25 @@ public function getProviderClassName(): string
 
     public function fetch(ImportConnector $connector): \Iterator
     {
-        return new \ArrayIterator(\json_decode(
-            (string)$connector->fetch(new HttpDataSource(self::getUrl())),
-            true
-        )['applist']['apps']);
+        $tries = -1;
+
+        retry:
+        if (++$tries === 10) {
+            throw new FetchAppListException("Could not fetch app list after $tries attempts.");
+        }
+
+        $json = \json_decode((string)$connector->fetch(new HttpDataSource(self::getUrl())), true);
+
+        if (isset($json['applist']['apps'])) {
+            $apps = $json['applist']['apps'];
+        }
+
+        // App list is empty about 20% of the time, seemingly more often on CI, so counting is important.
+        if ($json === null || !isset($apps) || !count($apps)) {
+            goto retry;
+        }
+
+        return new \ArrayIterator($apps);
     }
 
     public static function getUrl(): string