#3258777: Various fixes

• Add upcasting from migration ID to loaded migration plugin and config entity
• Tidy up theme preprocesses
• Tidy up composer.json
• Graphing is safer for Mermaid (strip out non :alnum: chars)
• Better detect missing graphviz

src/Controller/VisualizeController.php

@@ -4,8 +4,8 @@ namespace Drupal\migrate_visualize\Controller;
 
 use Drupal\Core\Controller\ControllerBase;
 use Drupal\migrate\Plugin\MigrationPluginManagerInterface;
+use Drupal\migrate_plus\Entity\Migration;
 use Drupal\migrate_visualize\MigrateGraph;
-use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 
 /**
@@ -52,25 +52,15 @@ class VisualizeController extends ControllerBase {
 
   /**
    * Visualize the migration.
-   *
-   * @todo Can the parameter be upcast?
-   * @see https://www.drupal.org/docs/8/api/routing-system/parameters-in-routes/how-upcasting-parameters-works
    */
-  public function build(string $migration) {
+  public function build(Migration $migration) {
+    $migrationPlugin = $this->migrationPluginManager->createInstance($migration->id(), $migration->toArray());
+
     $build['switcher'] = $this->formBuilder()
       ->getForm('Drupal\migrate_visualize\Form\VisualizeMigrationSwitcherForm');
 
-    $migrationInstance = $this->migrationPluginManager->createInstance($migration);
-    if ($migration !== '' && $migrationInstance === FALSE) {
-      $this->messenger()
-        ->addError($this->t('Migration not found: @migration', [
-          '@migration' => $migration,
-        ]));
-      throw new NotFoundHttpException();
-    }
-
     try {
-      $this->migrationGraph->graph($migrationInstance);
+      $this->migrationGraph->graph($migrationPlugin);
     }
     catch (\Exception $exception) {
       $this->messenger()
@@ -83,7 +73,7 @@ class VisualizeController extends ControllerBase {
     }
 
     $build['visualize'] = [
-      '#migration' => $migrationInstance,
+      '#migration' => $migrationPlugin,
       '#weight' => 110,
     ];