Issue #3021803 by alexpott, AaronBauman, effulgentsia, longwave, dawehner,...

Issue #3021803 by alexpott, AaronBauman, effulgentsia, longwave, dawehner, larowlan, bradjones1, tim.plunkett, Berdir, joachim, mondrake, weaverryan, JParkinson1991, kim.pepper, louis-cuny, rodrigoaguilera: Document and add tests for service autowiring

core/core.api.php

@@ -852,6 +852,12 @@
  * Services can also be defined dynamically, as in the
  * \Drupal\Core\CoreServiceProvider class, but this is less common for modules.
  *
+ * @section sec_define Service autowiring
+ * Instead of specifying arguments explicitly, the container can also autowire
+ * a service's arguments from the constructor's type-hints. See
+ * @link https://symfony.com/doc/current/service_container/autowiring.html the Symfony documentation on defining services dependencies automatically @endlink
+ * for details.
+ *
  * @section sec_tags Service tags
  * Some services have tags, which are defined in the service definition. See
  * @link service_tag Service Tags @endlink for usage.

core/misc/cspell/dictionary.txt

@@ -110,6 +110,7 @@ autosave
 autosubmit
 autowire
 autowired
+autowiring
 backend's
 backlink
 backlinks

core/modules/system/tests/modules/autowire_test/autowire_test.info.yml

+name: 'Auto-wiring test'
+type: module
+description: 'Support module for auto-wiring testing.'
+package: Testing
+version: VERSION

core/modules/system/tests/modules/autowire_test/autowire_test.services.yml

+services:
+  # Multiple services that implements TestInjectionInterface.
+  # These are marked private, because they are only intended to be used as
+  # dependencies injected into other services.
+  Drupal\autowire_test\TestInjection:
+    public: false
+  Drupal\autowire_test\TestInjection2:
+    public: false
+
+  # An alias that specifies which service to use by default for arguments that
+  # type-hint to the interface.
+  # This is marked private, because it is only intended to be used as a
+  # dependency injected into other services.
+  Drupal\autowire_test\TestInjectionInterface:
+    alias: 'Drupal\autowire_test\TestInjection'
+    public: false
+
+  # A service that tests autowiring for two constructor arguments:
+  # - One type-hinted to TestInjectionInterface.
+  # - One type-hinted to TestInjection2.
+  Drupal\autowire_test\TestService:
+    autowire: true

core/modules/system/tests/modules/autowire_test/src/TestInjection.php

+<?php
+
+namespace Drupal\autowire_test;
+
+/**
+ * A service that is autowired.
+ */
+class TestInjection implements TestInjectionInterface {
+}

core/modules/system/tests/modules/autowire_test/src/TestInjection2.php

+<?php
+
+namespace Drupal\autowire_test;
+
+/**
+ * A service that is autowired.
+ */
+class TestInjection2 {
+}

core/modules/system/tests/modules/autowire_test/src/TestInjectionInterface.php

+<?php
+
+namespace Drupal\autowire_test;
+
+/**
+ * An interface for a service that is autowired.
+ */
+interface TestInjectionInterface {
+}

core/modules/system/tests/modules/autowire_test/src/TestService.php

+<?php
+
+namespace Drupal\autowire_test;
+
+class TestService {
+
+  /**
+   * @var \Drupal\autowire_test\TestInjectionInterface
+   */
+  protected $testInjection;
+
+  /**
+   * @var \Drupal\autowire_test\TestInjection2
+   */
+  protected $testInjection2;
+
+  public function __construct(TestInjectionInterface $test_injection, TestInjection2 $test_injection2) {
+    $this->testInjection = $test_injection;
+    $this->testInjection2 = $test_injection2;
+  }
+
+  public function getTestInjection(): TestInjectionInterface {
+    return $this->testInjection;
+  }
+
+  public function getTestInjection2(): TestInjection2 {
+    return $this->testInjection2;
+  }
+
+}

core/tests/Drupal/KernelTests/Core/DependencyInjection/AutowireTest.php

+<?php
+
+namespace Drupal\KernelTests\Core\DependencyInjection;
+
+use Drupal\autowire_test\TestInjection;
+use Drupal\autowire_test\TestInjection2;
+use Drupal\autowire_test\TestService;
+use Drupal\KernelTests\KernelTestBase;
+
+/**
+ * Tests auto-wiring services.
+ *
+ * @group DependencyInjection
+ */
+class AutowireTest extends KernelTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['autowire_test'];
+
+  /**
+   * Tests that 'autowire_test.service' has its dependencies injected.
+   */
+  public function testAutowire(): void {
+    // Ensure an autowired interface works.
+    $this->assertInstanceOf(TestInjection::class, $this->container->get(TestService::class)->getTestInjection());
+    // Ensure an autowired class works.
+    $this->assertInstanceOf(TestInjection2::class, $this->container->get(TestService::class)->getTestInjection2());
+  }
+
+}