Issue #2661504 by yogeshmpawar, tim.plunkett, quietone, smustgrave: Document return values of Views render pipeline correctly

core/modules/views/src/Plugin/views/display/DisplayPluginBase.php

@@ -63,8 +63,10 @@ abstract class DisplayPluginBase extends PluginBase implements DisplayPluginInte
   /**
    * Stores the rendered output of the display.
    *
-   * @see View::render
-   * @var string
+   * @var array|null
+   *   Render output array, or NULL if no output.
+   *
+   * @see \Drupal\views\ViewExecutable::render()
    */
   public $output = NULL;
 

core/modules/views/src/Plugin/views/display/DisplayPluginInterface.php

@@ -391,6 +391,9 @@ interface DisplayPluginInterface {
 
   /**
    * Renders this display.
+   *
+   * @return array
+   *   A render array.
    */
   public function render();
 
@@ -495,6 +498,9 @@ interface DisplayPluginInterface {
    * Renders the display for the purposes of a live preview.
    *
    * Also might be used for some other AJAXy reason.
+   *
+   * @return array
+   *   The render array of live preview.
    */
   public function preview();