Update to Drupal 8.0-dev-2015-11-17. Commits through da81cd220, Tue Nov 17 15:53:49 2015 +0000, Issue #2617224 by Wim Leers: Move around/fix some documentation.

core/lib/Drupal/Core/Theme/MissingThemeDependencyException.php

@@ -0,0 +1,47 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Theme\MissingThemeDependencyException.
+ */
+
+namespace Drupal\Core\Theme;
+
+/**
+ * Exception to be thrown when base theme for installed theme is not installed.
+ *
+ * @see \Drupal\Core\Theme\ThemeInitialization::getActiveThemeByName().
+ */
+class MissingThemeDependencyException extends \Exception {
+
+  /**
+   * The missing theme dependency.
+   *
+   * @var string
+   */
+  protected $theme;
+
+  /**
+   * Constructs the exception.
+   *
+   * @param string $message
+   *   The exception message.
+   * @param string $theme
+   *   The missing theme dependency.
+   */
+  public function __construct($message, $theme) {
+    parent::__construct($message);
+    $this->theme = $theme;
+  }
+
+  /**
+   * Gets the machine name of the missing theme.
+   *
+   * @return string
+   *   The machine name of the theme that is missing.
+   */
+  public function getMissingThemeName() {
+    return $this->theme;
+  }
+
+}

core/lib/Drupal/Core/Theme/ThemeInitialization.php

@@ -109,6 +109,16 @@ class ThemeInitialization implements ThemeInitializationInterface {
     $ancestor = $theme_name;
     while ($ancestor && isset($themes[$ancestor]->base_theme)) {
       $ancestor = $themes[$ancestor]->base_theme;
+      if (!$this->themeHandler->themeExists($ancestor)) {
+        if ($ancestor == 'stable') {
+          // Themes that depend on Stable will be fixed by system_update_8014().
+          // There is no harm in not adding it as an ancestor since at worst
+          // some people might experience slight visual regressions on
+          // update.php.
+          continue;
+        }
+        throw new MissingThemeDependencyException(sprintf('Base theme %s has not been installed.', $ancestor), $ancestor);
+      }
       $base_themes[] = $themes[$ancestor];
     }
 

core/lib/Drupal/Core/Theme/ThemeInitializationInterface.php

@@ -34,6 +34,9 @@ interface ThemeInitializationInterface {
    *
    * @return \Drupal\Core\Theme\ActiveTheme
    *   An active theme object instance for the given theme.
+   *
+   * @throws \Drupal\Core\Theme\MissingThemeDependencyException
+   *   Thrown when base theme for installed theme is not installed.
    */
   public function getActiveThemeByName($theme_name);
 
@@ -54,8 +57,8 @@ interface ThemeInitializationInterface {
    * @param \Drupal\Core\Extension\Extension $theme
    *   The theme extension object.
    * @param \Drupal\Core\Extension\Extension[] $base_themes
-   *    An array of extension objects of base theme and its bases. It is ordered
-   *    by 'oldest first', meaning the top level of the chain will be first.
+   *   An array of extension objects of base theme and its bases. It is ordered
+   *   by 'next parent first', meaning the top level of the chain will be first.
    *
    * @return \Drupal\Core\Theme\ActiveTheme
    *   The active theme instance for the passed in $theme.