Issue #3254365 by Luke.Leber: Minify assets after aggregation

config/install/inline_all_css.settings.yml

 enabled: false
 enabled_themes: {  }
+minify: false

config/schema/inline_all_css.schema.yml

@@ -10,3 +10,6 @@ inline_all_css.settings:
       sequence:
         type: string
         label: 'Enabled theme'
+    minify:
+      type: boolean
+      label: 'Minify assets after aggregation'

inline_all_css.services.yml

@@ -11,3 +11,10 @@ services:
       - '@event_dispatcher'
       - '@http_client'
       - '@logger.factory'
+
+  inline_all_css_minify_subscriber:
+    class: Drupal\inline_all_css\EventSubscriber\MinifySubscriber
+    arguments:
+      - '@config.factory'
+    tags:
+      - { name: 'event_subscriber', priority: -1000 }

src/EventSubscriber/MinifySubscriber.php

+<?php
+
+namespace Drupal\inline_all_css\EventSubscriber;
+
+use Drupal\Core\Asset\CssOptimizer;
+use Drupal\Core\Config\ConfigFactoryInterface;
+use Drupal\inline_all_css\Event\CssPreRenderEvent;
+use Symfony\Component\EventDispatcher\EventSubscriberInterface;
+
+/**
+ * An event subscriber that minifies the aggregated source.
+ */
+class MinifySubscriber extends CssOptimizer implements EventSubscriberInterface {
+
+  /**
+   * The module configuration.
+   *
+   * @var \Drupal\Core\Config\ImmutableConfig
+   */
+  protected $config;
+
+  /**
+   * Creates an event subscriber instance.
+   *
+   * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
+   *   The config factory service.
+   */
+  public function __construct(ConfigFactoryInterface $config_factory) {
+    $this->config = $config_factory->get('inline_all_css.settings');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function getSubscribedEvents() {
+    return [
+      CssPreRenderEvent::EVENT_NAME => 'onCssPreRender',
+    ];
+  }
+
+  /**
+   * Optimizes the CSS that is being inlined.
+   *
+   * @param \Drupal\inline_all_css\Event\CssPreRenderEvent $event
+   *   The css pre-render event.
+   */
+  public function onCssPreRender(CssPreRenderEvent $event) {
+    if ($this->config->get('minify') === TRUE) {
+      $css = $event->getCss();
+      $css = $this->processCss($css, TRUE);
+      $event->setCss($css);
+    }
+  }
+
+}

src/Form/SettingsForm.php

@@ -79,6 +79,18 @@ HTML,
       ],
     ];
 
+    $form['minify'] = [
+      '#type' => 'checkbox',
+      '#title' => $this->t('Minify'),
+      '#description' => $this->t('If selected, assets will be minified after aggregation'),
+      '#default_value' => $config->get('minify'),
+      '#states' => [
+        'visible' => [
+          ':input[name="enabled"]' => ['checked' => TRUE],
+        ],
+      ],
+    ];
+
     return parent::buildForm($form, $form_state);
   }
 
@@ -98,6 +110,7 @@ HTML,
     $enabled_themes = array_filter($enabled_themes);
 
     $config->set('enabled_themes', $enabled_themes);
+    $config->set('minify', $form_state->getValue('minify'));
     $config->save();
     parent::submitForm($form, $form_state);
   }

tests/src/Unit/MinifySubscriberTest.php

+<?php
+
+namespace Drupal\Tests\inline_all_css\Unit;
+
+use Drupal\Core\Config\ConfigFactoryInterface;
+use Drupal\Core\Config\ImmutableConfig;
+use Drupal\inline_all_css\Event\CssPreRenderEvent;
+use Drupal\inline_all_css\EventSubscriber\MinifySubscriber;
+use Drupal\Tests\UnitTestCase;
+
+/**
+ * Test cases for the minify subscriber.
+ *
+ * @group inline_all_csss
+ */
+class MinifySubscriberTest extends UnitTestCase {
+
+  /**
+   * The expected events.
+   */
+  protected const EXPECTED_EVENTS = [
+    CssPreRenderEvent::EVENT_NAME => 'onCssPreRender',
+  ];
+
+  /**
+   * The non-minified source.
+   */
+  protected const SOURCE = <<<CSS
+* {
+  background-color: pink;
+}
+CSS;
+
+  /**
+   * The minified source.
+   */
+  protected const MINIFIED = <<<CSS
+*{background-color:pink;}
+
+CSS;
+
+  /**
+   * The subject under test.
+   *
+   * @var \Drupal\inline_all_css\EventSubscriber\MinifySubscriber
+   */
+  protected $instance;
+
+  /**
+   * The enable flag for minification.
+   *
+   * @var bool
+   */
+  protected $minificationEnabled;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+
+    $config = $this->getMockBuilder(ImmutableConfig::class)
+      ->disableOriginalConstructor()
+      ->getMock();
+
+    $config
+      ->method('get')
+      ->willReturnCallback(function () {
+        return $this->minificationEnabled;
+      });
+
+    $config_factory = $this->getMockBuilder(ConfigFactoryInterface::class)
+      ->disableOriginalConstructor()
+      ->getMock();
+
+    $config_factory
+      ->method('get')
+      ->willReturn($config);
+
+    $this->instance = new MinifySubscriber($config_factory);
+
+  }
+
+  /**
+   * Test case for the minify subscriber.
+   */
+  public function testMinifySubscriber() {
+
+    // Ensure the proper events are subscribed to.
+    static::assertSame(static::EXPECTED_EVENTS, MinifySubscriber::getSubscribedEvents());
+
+    $event = new CssPreRenderEvent(static::SOURCE);
+
+    // Ensure minification does not run if disabled.
+    $this->minificationEnabled = FALSE;
+    $this->instance->onCssPreRender($event);
+    static::assertSame(static::SOURCE, $event->getCss());
+
+    // Ensure minification does run if enabled.
+    $this->minificationEnabled = TRUE;
+    $this->instance->onCssPreRender($event);
+    static::assertSame(static::MINIFIED, $event->getCss());
+  }
+
+}