core/modules/ckeditor/ckeditor.module              |  4 ++
 .../Plugin/CKEditorPlugin/DrupalImageCaption.php   |  4 ++
 .../ckeditor/Plugin/CKEditorPlugin/Internal.php    |  9 ++-
 .../Drupal/ckeditor/Tests/CKEditorAdminTest.php    | 68 +++++++++++++++++++++-
 .../editor/lib/Drupal/editor/EditorInterface.php   | 16 ++++-
 .../editor/lib/Drupal/editor/Entity/Editor.php     |  7 +++
 .../lib/Drupal/filter/FilterFormatInterface.php    |  2 +-
 7 files changed, 106 insertions(+), 4 deletions(-)

diff --git a/core/modules/ckeditor/ckeditor.module b/core/modules/ckeditor/ckeditor.module
index aa793aa..eb646c9 100644
--- a/core/modules/ckeditor/ckeditor.module
+++ b/core/modules/ckeditor/ckeditor.module
@@ -49,6 +49,10 @@ function ckeditor_theme() {
  * Implements hook_ckeditor_css_alter().
  */
 function ckeditor_ckeditor_css_alter(array &$css, Editor $editor) {
+  if (!$editor->hasAssociatedFilterFormat()) {
+    return;
+  }
+
   // Add the filter caption CSS if the text format associated with this text
   // editor uses the filter_caption filter. This is used by the included
   // CKEditor DrupalImageCaption plugin.
diff --git a/core/modules/ckeditor/lib/Drupal/ckeditor/Plugin/CKEditorPlugin/DrupalImageCaption.php b/core/modules/ckeditor/lib/Drupal/ckeditor/Plugin/CKEditorPlugin/DrupalImageCaption.php
index 0b753e8..5c2fffa 100644
--- a/core/modules/ckeditor/lib/Drupal/ckeditor/Plugin/CKEditorPlugin/DrupalImageCaption.php
+++ b/core/modules/ckeditor/lib/Drupal/ckeditor/Plugin/CKEditorPlugin/DrupalImageCaption.php
@@ -68,6 +68,10 @@ public function getConfig(Editor $editor) {
    * {@inheritdoc}
    */
   function isEnabled(Editor $editor) {
+    if (!$editor->hasAssociatedFilterFormat()) {
+      return FALSE;
+    }
+
     // Automatically enable this plugin if the text format associated with this
     // text editor uses the filter_caption filter and the DrupalImage button is
     // enabled.
diff --git a/core/modules/ckeditor/lib/Drupal/ckeditor/Plugin/CKEditorPlugin/Internal.php b/core/modules/ckeditor/lib/Drupal/ckeditor/Plugin/CKEditorPlugin/Internal.php
index 78b725e..7272357 100644
--- a/core/modules/ckeditor/lib/Drupal/ckeditor/Plugin/CKEditorPlugin/Internal.php
+++ b/core/modules/ckeditor/lib/Drupal/ckeditor/Plugin/CKEditorPlugin/Internal.php
@@ -289,9 +289,16 @@ protected function generateFormatTagsSetting(Editor $editor) {
    *     array or FALSE. The latter indicates that nothing is disallowed.
    */
   protected function generateACFSettings(Editor $editor) {
-    // When nothing is disallowed, set allowedContent to true.
+    // When no text format is associated yet, assume nothing is disallowed, so
+    // set allowedContent to true.
+    if (!$editor->hasAssociatedFilterFormat()) {
+      return TRUE;
+    }
+
     $format = $editor->getFilterFormat();
     $filter_types = $format->getFilterTypes();
+
+    // When nothing is disallowed, set allowedContent to true.
     if (!in_array(FilterInterface::TYPE_HTML_RESTRICTOR, $filter_types)) {
       return array(TRUE, FALSE);
     }
diff --git a/core/modules/ckeditor/lib/Drupal/ckeditor/Tests/CKEditorAdminTest.php b/core/modules/ckeditor/lib/Drupal/ckeditor/Tests/CKEditorAdminTest.php
index 4680f9e..0d2d5b2 100644
--- a/core/modules/ckeditor/lib/Drupal/ckeditor/Tests/CKEditorAdminTest.php
+++ b/core/modules/ckeditor/lib/Drupal/ckeditor/Tests/CKEditorAdminTest.php
@@ -8,6 +8,7 @@
 namespace Drupal\ckeditor\Tests;
 
 use Drupal\editor\Entity\Editor;
+use Drupal\filter\FilterFormatInterface;
 use Drupal\simpletest\WebTestBase;
 
 /**
@@ -46,7 +47,10 @@ function setUp() {
     $this->admin_user = $this->drupalCreateUser(array('administer filters'));
   }
 
-  function testAdmin() {
+  /**
+   * Tests configuring a text editor for an existing text format.
+   */
+  function testExistingFormat() {
     $ckeditor = $this->container->get('plugin.manager.editor')->createInstance('ckeditor');
 
     $this->drupalLogin($this->admin_user);
@@ -187,4 +191,66 @@ function testAdmin() {
     $this->assertIdentical($expected_settings, $editor->getSettings());
   }
 
+  /**
+   * Tests configuring a text editor for a new text format.
+   *
+   * This test only needs to ensure that the basics of the CKEditor
+   * configuration form work; details are tested in testExistingFormat().
+   */
+  function testNewFormat() {
+    $this->drupalLogin($this->admin_user);
+    $this->drupalGet('admin/config/content/formats/add');
+
+    // Verify the "Text Editor" <select> when a text editor is available.
+    $select = $this->xpath('//select[@name="editor[editor]"]');
+    $select_is_disabled = $this->xpath('//select[@name="editor[editor]" and @disabled="disabled"]');
+    $options = $this->xpath('//select[@name="editor[editor]"]/option');
+    $this->assertTrue(count($select) === 1, 'The Text Editor select exists.');
+    $this->assertTrue(count($select_is_disabled) === 0, 'The Text Editor select is not disabled.');
+    $this->assertTrue(count($options) === 2, 'The Text Editor select has two options.');
+    $this->assertTrue(((string) $options[0]) === 'None', 'Option 1 in the Text Editor select is "None".');
+    $this->assertTrue(((string) $options[1]) === 'CKEditor', 'Option 2 in the Text Editor select is "CKEditor".');
+    $this->assertTrue(((string) $options[0]['selected']) === 'selected', 'Option 1 ("None") is selected.');
+
+    // Name our fancy new text format, select the "CKEditor" editor and click
+    // the "Configure" button.
+    $edit = array(
+      'name' => 'My amazing text format',
+      'format' => 'amazing_format',
+      'editor[editor]' => 'ckeditor',
+    );
+    $this->drupalPostAjaxForm(NULL, $edit, 'editor_configure');
+    $filter_format = entity_load('filter_format', 'amazing_format');
+    $this->assertFalse($filter_format, 'No FilterFormat config entity exists yet.');
+    $editor = entity_load('editor', 'amazing_format');
+    $this->assertFalse($editor, 'No Editor config entity exists yet.');
+
+    // Ensure the toolbar buttons configuration value is initialized to the
+    // default value.
+    $ckeditor = $this->container->get('plugin.manager.editor')->createInstance('ckeditor');
+    $default_settings = $ckeditor->getDefaultSettings();
+    $expected_buttons_value = json_encode($default_settings['toolbar']['rows']);
+    $this->assertFieldByName('editor[settings][toolbar][button_groups]', $expected_buttons_value);
+
+    // Ensure the styles textarea exists and is initialized empty.
+    $styles_textarea = $this->xpath('//textarea[@name="editor[settings][plugins][stylescombo][styles]"]');
+    $this->assertFieldByXPath('//textarea[@name="editor[settings][plugins][stylescombo][styles]"]', '', 'The styles textarea exists and is empty.');
+    $this->assertTrue(count($styles_textarea) === 1, 'The "styles" textarea exists.');
+
+    // Submit the form to create both a new text format and an associated text
+    // editor.
+    $this->drupalPostForm(NULL, $edit, t('Save configuration'));
+
+    // Ensure a FilterFormat object exists now.
+    $filter_format = entity_load('filter_format', 'amazing_format');
+    $this->assertTrue($filter_format instanceof FilterFormatInterface, 'A FilterFormat config entity exists now.');
+
+    // Ensure an Editor object exists now, with the proper settings.
+    $expected_settings = $default_settings;
+    $expected_settings['plugins']['stylescombo']['styles'] = '';
+    $editor = entity_load('editor', 'amazing_format');
+    $this->assertTrue($editor instanceof Editor, 'An Editor config entity exists now.');
+    $this->assertIdentical($expected_settings, $editor->getSettings(), 'The Editor config entity has the correct settings.');
+  }
+
 }
diff --git a/core/modules/editor/lib/Drupal/editor/EditorInterface.php b/core/modules/editor/lib/Drupal/editor/EditorInterface.php
index 7847011..1631ec9 100644
--- a/core/modules/editor/lib/Drupal/editor/EditorInterface.php
+++ b/core/modules/editor/lib/Drupal/editor/EditorInterface.php
@@ -15,9 +15,23 @@
 interface EditorInterface extends ConfigEntityInterface {
 
   /**
+   * Returns whether this text editor has an associated filter format.
+   *
+   * A text editor may be created at the same time as the filter format it's
+   * going to be associated with; in that case, no filter format object is
+   * available yet.
+   *
+   * @return bool
+   */
+  public function hasAssociatedFilterFormat();
+
+  /**
    * Returns the filter format this text editor is associated with.
    *
-   * @return \Drupal\filter\FilterFormatInterface
+   * This could be NULL if the associated filter format is still being created.
+   * @see hasAssociatedFilterFormat()
+   *
+   * @return \Drupal\filter\FilterFormatInterface|null
    */
   public function getFilterFormat();
 
diff --git a/core/modules/editor/lib/Drupal/editor/Entity/Editor.php b/core/modules/editor/lib/Drupal/editor/Entity/Editor.php
index 8378102..40aff70 100644
--- a/core/modules/editor/lib/Drupal/editor/Entity/Editor.php
+++ b/core/modules/editor/lib/Drupal/editor/Entity/Editor.php
@@ -105,6 +105,13 @@ public function calculateDependencies() {
   /**
    * {@inheritdoc}
    */
+  public function hasAssociatedFilterFormat() {
+    return $this->format !== NULL;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
   public function getFilterFormat() {
     if (!$this->filterFormat) {
       $this->filterFormat = \Drupal::entityManager()->getStorage('filter_format')->load($this->format);
diff --git a/core/modules/filter/lib/Drupal/filter/FilterFormatInterface.php b/core/modules/filter/lib/Drupal/filter/FilterFormatInterface.php
index df93354..e0b3c84 100644
--- a/core/modules/filter/lib/Drupal/filter/FilterFormatInterface.php
+++ b/core/modules/filter/lib/Drupal/filter/FilterFormatInterface.php
@@ -2,7 +2,7 @@
 
 /**
  * @file
- * Contains \Drupal\filter\Entity\FilterFormatInterface.
+ * Contains \Drupal\filter\FilterFormatInterface.
  */
 
 namespace Drupal\filter;