Surface some Conditions in Block Visibility (#1084) (for phasing out display contexts)

* let 'node_has_term' and 'node_is_islandora_object' be in block visibility conditions

* add config field to NodeIsIslandoraObject condition

Conditions only get applied in Block Visibility when there's a config
change for that condition in the block config form, so it needs a field
to configure.

* more informative field description

* some cleanup to config for NodeIsIslandoraObject

Much thanks to @adam-vessey for helping to figure this out!

* cleanup default config for MediaSourceHasMimetype

Might as well get this cleaned up so it stops inserting itself in all
the block configs where it's not relevant.

* remove unused use statement

Author: JojoVes

islandora.module

@@ -509,8 +509,6 @@ function islandora_form_block_form_alter(&$form, FormStateInterface $form_state,
   unset($form['visibility']['node_had_namespace']);
   unset($form['visibility']['node_has_ancestor']);
   unset($form['visibility']['node_has_parent']);
-  unset($form['visibility']['node_has_term']);
-  unset($form['visibility']['node_is_islandora_object']);
   unset($form['visibility']['node_referenced_by_node']);
   unset($form['visibility']['parent_node_has_term']);
 }

src/Plugin/Condition/MediaSourceHasMimetype.php

@@ -85,7 +85,7 @@ public function summary() {
    */
   public function defaultConfiguration() {
     return array_merge(
-      ['mimetype' => []],
+      ['mimetype' => ""],
       parent::defaultConfiguration()
     );
   }

src/Plugin/Condition/NodeIsIslandoraObject.php

@@ -14,7 +14,11 @@
  *   id = "node_is_islandora_object",
  *   label = @Translation("Node is an Islandora node"),
  *   context_definitions = {
- *     "node" = @ContextDefinition("entity:node", required = TRUE , label = @Translation("node"))
+ *     "node" = @ContextDefinition("entity:node",
+ *       required = FALSE,
+ *       label = @Translation("Node source"),
+ *       description = @Translation("The node source must be set for this condition to work as expected.")
+ *     )
  *   }
  * )
  */
@@ -56,6 +60,28 @@ public static function create(ContainerInterface $container, array $configuratio
     );
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function defaultConfiguration() {
+    $defaults = parent::defaultConfiguration();
+
+    // XXX: There appear to be expectations in Drupal that there will be more
+    // config to a plugin than just selecting the context mapping; however, it
+    // is our only configuration. Due to these expectations, it would fail to
+    // save our visibility settings. To work around, it seems to be sufficient
+    // to dynamically declare our default configuration, such that the
+    // difference from the default configuration can be detected upstream.
+    // @see https://git.drupalcode.org/project/drupal/-/blob/d87ab76d397a2cfe0457997be4f2648c4760b2f5/core/lib/Drupal/Core/Condition/ConditionPluginCollection.php#L39-44
+    if (!empty($this->configuration['context_mapping'])) {
+      $defaults += [
+        'context_mapping' => [],
+      ];
+    }
+
+    return $defaults;
+  }
+
   /**
    * {@inheritdoc}
    */