Issue #2896427 by marcoscano, Wim Leers, xjm, Berdir, slashrsm: Prevent...

Issue #2896427 by marcoscano, Wim Leers, xjm, Berdir, slashrsm: Prevent enabling the "media" module if "media_entity" contrib 1.x is already enabled

core/modules/media/media.install

@@ -68,6 +68,21 @@ function media_requirements($phase) {
         $requirements['media']['severity'] = REQUIREMENT_ERROR;
       }
     }
+
+    // Prevent installation if the 1.x branch of the contrib module is enabled.
+    if (\Drupal::moduleHandler()->moduleExists('media_entity')) {
+      $info = system_get_info('module', 'media_entity');
+      if (version_compare($info['version'], '8.x-2') < 0) {
+        $requirements['media_module_incompatibility'] = [
+          'title' => t('Media'),
+          'description' => t('The Media module is not compatible with contrib <a href=":url">Media Entity</a> 1.x branch. Please check the 2.x branch of that module for an upgrade path.', [
+            ':url' => 'https://drupal.org/project/media_entity',
+          ]),
+          'severity' => REQUIREMENT_ERROR,
+        ];
+      }
+    }
   }
+
   return $requirements;
 }