Deal with bad theme config more gracefully.

module/VuFind/src/VuFind/Bootstrapper.php

@@ -241,12 +241,20 @@ protected function initUserLanguage(): void
      */
     protected function initTheme(): void
     {
-        // Attach remaining theme configuration to the dispatch event at high
-        // priority (TODO: use priority constant once defined by framework):
-        $config = $this->config->Site;
-        $callback = function ($event) use ($config) {
-            $theme = new \VuFindTheme\Initializer($config, $event);
-            $theme->init();
+        // Attach remaining theme configuration to the dispatch event at high priority:
+        $siteConfig = $this->config->Site;
+        $callback = function ($event) use ($siteConfig) {
+            $theme = new \VuFindTheme\Initializer($siteConfig, $event);
+            try {
+                $theme->init();
+            } catch (\Exception $e) {
+                // Try to display an error page if the theme fails to initialize:
+                $appConfig = $this->container->get('config');
+                $model = $event->getViewModel();
+                $model->setTemplate('error/index');
+                $model->display_exceptions = $appConfig['view_manager']['display_exceptions'] ?? false;
+                $model->exception = $e;
+            }
         };
         $this->events->attach('dispatch.error', $callback, 9000);
         $this->events->attach('dispatch', $callback, 9000);

module/VuFind/tests/integration-tests/src/VuFindTest/Mink/BasicTest.php

@@ -48,7 +48,7 @@ class BasicTest extends \VuFindTest\Integration\MinkTestCase
     public function testHomePage(): void
     {
         $page = $this->getSearchHomePage();
-        $this->assertTrue(false !== strstr($page->getContent(), 'VuFind'));
+        $this->assertStringContainsString('VuFind', $page->getContent());
     }
 
     /**
@@ -142,6 +142,31 @@ public function testThemeSwitcher(): void
         );
     }
 
+    /**
+     * Test graceful handling of an invalid theme.
+     *
+     * Note that HTML validation is disabled on this test because an improperly initialized
+     * theme will not generate a fully-formed page; but we still want to confirm that it
+     * at least outputs a human-readable error message.
+     *
+     * @return void
+     */
+    #[\VuFindTest\Attribute\HtmlValidation(false)]
+    public function testBadThemeConfig(): void
+    {
+        $this->changeConfigs(
+            [
+                'config' => [
+                    'Site' => [
+                        'theme' => 'not-a-valid-theme',
+                    ],
+                ],
+            ]
+        );
+        $page = $this->getSearchHomePage();
+        $this->assertStringContainsString('An error has occurred', $page->getContent());
+    }
+
     /**
      * Test lightbox jump links
      *

module/VuFindTheme/src/VuFindTheme/ThemeInfoFactory.php

@@ -71,7 +71,7 @@ public function __invoke(
 
         $themeInfo = new $requestedName(
             realpath(APPLICATION_PATH . '/themes'),
-            'bootprint3'
+            'sandal5'
         );
 
         // As of release 1.1.0, the memory storage adapter has a flaw which can cause