Issue #2845024 by tlyngej, jrockowitz: Add hook_config_ignore_alter(&$names)

config_ignore.api.php

+<?php
+
+/**
+ * @file
+ * Hooks specific to the Config Ignore module.
+ */
+
+/**
+ * @addtogroup hooks
+ * @{
+ */
+
+/**
+ * Alter the list of config entities that should be ignored.
+ */
+function hook_config_ignore_settings_alter(array &$settings) {
+  $settings[] = 'system.site';
+  $settings[] = 'field.*';
+}
+
+/**
+ * @} End of "addtogroup hooks".
+ */

src/ConfigImporterIgnore.php

@@ -27,6 +27,7 @@ class ConfigImporterIgnore {
   public static function preImport(array &$context, ConfigImporter $config_importer) {
     $config_to_ignore = [];
     $config_ignore_settings = \Drupal::config('config_ignore.settings')->get('ignored_config_entities');
+    \Drupal::moduleHandler()->invokeAll('config_ignore_settings_alter', [&$config_ignore_settings]);
     foreach (['delete', 'create', 'rename', 'update'] as $op) {
       // For now, we only support updates.
       if ($op == 'update') {

src/Tests/ConfigIgnoreHookTest.php

+<?php
+
+namespace Drupal\config_ignore\Tests;
+
+use Drupal\simpletest\WebTestBase;
+use Drupal\Core\Serialization\Yaml;
+
+/**
+ * Test hooks that this module implements.
+ *
+ * This must be a simpletest test as it does not seem that the PHPUnit
+ * implementation for Drupal supports batch processing yet.
+ *
+ * @package Drupal\config_ignore\Tests
+ *
+ * @group config_ignore
+ */
+class ConfigIgnoreHookTest extends WebTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  public static $modules = ['config_ignore_hook_test'];
+
+  /**
+   * The profile to install as a basis for testing.
+   *
+   * We need to change it form the standard 'testing' profile as that will not
+   * print the title on the page, which we use for testing.
+   *
+   * @var string
+   */
+  protected $profile = 'minimal';
+
+  /**
+   * Verify that hook_config_ignore_settings_alter are getting called.
+   */
+  public function testSettingsAlterHook() {
+
+    // Login with a user that has permission to import config.
+    $this->drupalLogin($this->drupalCreateUser(['import configuration']));
+
+    // Set the site name to a known value that we later will try and overwrite.
+    $this->config('system.site')->set('name', 'Test import title')->save();
+
+    // Assemble a change that will try and override the current value.
+    $config = $this->config('system.site')->set('name', 'Import has changed title');
+
+    $edit = [
+      'config_type' => 'system.simple',
+      'config_name' => $config->getName(),
+      'import' => Yaml::encode($config->get()),
+    ];
+
+    // Submit a new single item config, with the changes.
+    $this->drupalPostForm('admin/config/development/configuration/single/import', $edit, t('Import'));
+    $this->drupalPostForm(NULL, [], t('Confirm'));
+
+    // Validate if the title from the imported config was rejected, due to the
+    // hook implemented in the `config_ignore_hook_test` module.
+    $this->drupalGet('<front>');
+    $this->assertText('Test import title');
+  }
+
+}

tests/config_ignore_hook_test/config_ignore_hook_test.info.yml

+name: Config Ignore Hook Test
+type: module
+description: Module that implements all the hook from Config Ignore for testing purposes
+core: 8.x
+package: Configuration
+dependencies:
+  - config_ignore

tests/config_ignore_hook_test/config_ignore_hook_test.module

+<?php
+
+/**
+ * @file
+ * Module that implements all the hook from Config Ignore for testing purposes.
+ */
+
+/**
+ * Implements hook_config_ignore_settings_alter().
+ */
+function config_ignore_hook_test_config_ignore_settings_alter(array &$settings) {
+  $settings[] = 'system.site';
+}