Issue #2598304 by Tom Verhaeghe, borisson_, brentgees: Create Facet processors...

Issue #2598304 by Tom Verhaeghe, borisson_, brentgees: Create Facet processors - Show only deepest level items

src/Plugin/facets/processor/ShowOnlyDeepestLevelItemsProcessor.php

+<?php
+
+namespace Drupal\facets\Plugin\facets\processor;
+
+use Drupal\facets\FacetInterface;
+use Drupal\facets\Processor\BuildProcessorInterface;
+use Drupal\facets\Processor\ProcessorPluginBase;
+
+/**
+ * Provides a processor that only shows deepest level items.
+ *
+ * @FacetsProcessor(
+ *   id = "show_only_deepest_level_items_processor",
+ *   label = @Translation("Show only deepest item levels"),
+ *   description = @Translation("Only show items that have no children."),
+ *   stages = {
+ *     "build" = 40
+ *   }
+ * )
+ */
+class ShowOnlyDeepestLevelItemsProcessor extends ProcessorPluginBase implements BuildProcessorInterface {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function build(FacetInterface $facet, array $results) {
+    /** @var \Drupal\facets\Result\ResultInterface $result */
+    foreach ($results as $id => $result) {
+      if (!empty($result->getChildren())) {
+        unset($results[$id]);
+      }
+    }
+    return $results;
+  }
+
+}

tests/src/Unit/Plugin/processor/ShowOnlyDeepestLevelItemsProcessorTest.php

+<?php
+
+namespace Drupal\Tests\facets\Unit\Plugin\processor;
+
+use Drupal\facets\Entity\Facet;
+use Drupal\facets\Plugin\facets\processor\ShowOnlyDeepestLevelItemsProcessor;
+use Drupal\facets\Result\Result;
+use Drupal\Tests\UnitTestCase;
+
+/**
+ * Class ShowOnlyDeepestLevelItemsProcessorTest.
+ *
+ * @group facets
+ * @coversDefaultClass \Drupal\facets\Plugin\facets\processor\ShowOnlyDeepestLevelItemsProcessor
+ */
+class ShowOnlyDeepestLevelItemsProcessorTest extends UnitTestCase {
+
+  /**
+   * @var \Drupal\facets\Plugin\facets\processor\ShowOnlyDeepestLevelItemsProcessor
+   */
+  protected $processor;
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setUp() {
+    parent::setUp();
+    $this->processor = new ShowOnlyDeepestLevelItemsProcessor([], 'test', []);
+  }
+
+  /**
+   * Tests that only items without children survive.
+   *
+   * @covers ::build
+   */
+  public function testRemoveItemsWithoutChildren() {
+    $facet = new Facet(['id' => 'llama'], 'facets_facet');
+    // Setup results.
+    $results = [
+      new Result($facet, 'a', 'A', 5),
+      new Result($facet, 'b', 'B', 2),
+      new Result($facet, 'c', 'C', 4),
+    ];
+    $child = new Result($facet, 'a_1', 'A 1', 3);
+    $results[0]->setChildren([$child]);
+
+    // Execute the build method, so we can test the behavior.
+    $built_results = $this->processor->build($facet, $results);
+
+    // Sort to have a 0-indexed array.
+    sort($built_results);
+
+    // Check the output.
+    $this->assertCount(2, $built_results);
+    $this->assertSame('b', $built_results[0]->getRawValue());
+    $this->assertSame('c', $built_results[1]->getRawValue());
+  }
+
+}