Issue #2679008 by webflo, stBorchert, clemens.tolboom, gilesmc, dawehner: Module weight is not taken into account after module installation

core/lib/Drupal/Core/Extension/ModuleInstaller.php

@@ -136,6 +136,10 @@ class ModuleInstaller implements ModuleInstallerInterface {
           throw new ExtensionNameLengthException("Module name '$module' is over the maximum allowed length of " . DRUPAL_EXTENSION_NAME_MAX_LENGTH . ' characters');
         }
 
+        // Load a new config object for each iteration, otherwise changes made
+        // in hook_install() are not reflected in $extension_config.
+        $extension_config = \Drupal::configFactory()->getEditable('core.extension');
+
         // Check the validity of the default configuration. This will throw
         // exceptions if the configuration is not valid.
         $config_installer->checkConfigurationToInstall('module', $module);

core/modules/system/tests/modules/module_handler_test_multiple/module_handler_test_multiple.install

@@ -0,0 +1,14 @@
+<?php
+
+/**
+ * @file
+ * Install, update and uninstall functions for the module_handler_test_multiple module.
+ */
+
+/**
+ * Implements hook_install().
+ */
+function module_handler_test_multiple_install() {
+  // Set weight of module.
+  module_set_weight('module_handler_test_multiple', 1);
+}

core/modules/system/tests/modules/module_handler_test_multiple/module_handler_test_multiple_child/module_handler_test_multiple_child.info.yml

@@ -5,3 +5,5 @@ package: Testing
 version: VERSION
 core: 8.x
 hidden: true
+dependencies:
+  - module_handler_test_multiple

core/modules/system/tests/modules/module_handler_test_multiple/module_handler_test_multiple_child/module_handler_test_multiple_child.install

@@ -0,0 +1,17 @@
+<?php
+
+/**
+ * @file
+ * Utility functions for the module_handler_test_multiple_child module.
+ *
+ * Install, update and uninstall functions for the
+ * module_handler_test_multiple_child module.
+ */
+
+/**
+ * Implements hook_install().
+ */
+function module_handler_test_multiple_child_install() {
+  // Set weight of module.
+  module_set_weight('module_handler_test_multiple_child', 1);
+}

core/tests/Drupal/KernelTests/Core/Extension/ModuleInstallerTest.php

@@ -44,4 +44,20 @@ class ModuleInstallerTest extends KernelTestBase {
     $this->container->get('router.route_provider')->getRouteByName('router_test.1');
   }
 
+  /**
+   * Tests config changes by hook_install() are saved for dependent modules.
+   *
+   * @covers ::install
+   */
+  public function testConfigChangeOnInstall() {
+    // Install the child module so the parent is installed automatically.
+    $this->container->get('module_installer')->install(['module_handler_test_multiple_child']);
+    $modules = $this->config('core.extension')->get('module');
+
+    $this->assertArrayHasKey('module_handler_test_multiple', $modules, 'Module module_handler_test_multiple is installed');
+    $this->assertArrayHasKey('module_handler_test_multiple_child', $modules, 'Module module_handler_test_multiple_child is installed');
+    $this->assertEquals(1, $modules['module_handler_test_multiple'], 'Weight of module_handler_test_multiple is set.');
+    $this->assertEquals(1, $modules['module_handler_test_multiple_child'], 'Weight of module_handler_test_multiple_child is set.');
+  }
+
 }