Issue #2387983 by Garrett Albright, larowlan: PluginNotFoundException when enabling module that provides text filter

core/modules/filter/filter.module

@@ -100,8 +100,14 @@ function filter_system_info_alter(&$info, Extension $file, $type) {
       $used_in = [];
       // Find out if any filter formats have the plugin enabled.
       foreach (filter_formats() as $filter_format) {
-        foreach ($filter_plugins as $filter_plugin) {
-          if ($filter_format->filters($filter_plugin['id'])->status) {
+        $filters = $filter_format->filters();
+        // Typically, all formats will contain settings for all filter plugins,
+        // even if they are disabled. However, if a module which provides filter
+        // plugins is being enabled right now, that won't be the case, so we
+        // still check to see if this format has this filter before we check
+        // the filter status.
+       foreach ($filter_plugins as $filter_plugin) {
+          if ($filters->has($filter_plugin['id']) && $filters->get($filter_plugin['id'])->status) {
             $used_in[] = $filter_format->label();
             $info['required'] = TRUE;
             break;

core/modules/filter/src/Tests/FilterFormTest.php

@@ -71,6 +71,12 @@ class FilterFormTest extends WebTestBase {
   public function testFilterForm() {
     $this->doFilterFormTestAsAdmin();
     $this->doFilterFormTestAsNonAdmin();
+    // Ensure that enabling modules which provide filter plugins behaves
+    // correctly.
+    // @see https://www.drupal.org/node/2387983
+    \Drupal::service('module_installer')->install(['filter_test_plugin']);
+    // Force rebuild module data.
+    _system_rebuild_module_data();
   }
 
   /**

core/modules/filter/tests/filter_test_plugin/filter_test_plugin.info.yml

@@ -0,0 +1,6 @@
+name: 'Filter test plugin'
+type: module
+description: 'Tests enabling of modules which provide filter plugins.'
+package: Testing
+version: VERSION
+core: 8.x

core/modules/filter/tests/filter_test_plugin/src/Plugin/Filter/FilterSparkles.php

@@ -0,0 +1,38 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\filter_test_plugin\Plugin\Filter\FilterSparkles.
+ *
+ * This filter does not do anything, but enabling of its module is done in a
+ * test.
+ *
+ * @see \Drupal\filter\Tests\FilterFormTest::testFilterForm()
+ */
+
+namespace Drupal\filter_test_plugin\Plugin\Filter;
+
+use Drupal\filter\FilterProcessResult;
+use Drupal\filter\Plugin\FilterBase;
+
+/**
+ * Provides a filter to limit allowed HTML tags.
+ *
+ * @Filter(
+ *   id = "filter_sparkles",
+ *   title = @Translation("Sparkles filter"),
+ *   type = Drupal\filter\Plugin\FilterInterface::TYPE_HTML_RESTRICTOR,
+ *   settings = {},
+ *   weight = -10
+ * )
+ */
+class FilterSparkles extends FilterBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function process($text, $langcode) {
+    return new FilterProcessResult($text);
+  }
+
+}