feat(query): add has child joining query

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: Spamercz

doc/02-query-objects.md

@@ -340,6 +340,27 @@ new \Spameri\ElasticQuery\Query\Boosting(
 
 ---
 
+## Joining Queries
+
+Queries that traverse parent/child or join relationships.
+
+##### HasChild Query
+Match parents whose children match the inner query.
+- Class: `\Spameri\ElasticQuery\Query\HasChild`
+- [Documentation](https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-has-child-query.html)
+- [Implementation](https://github.com/Spameri/ElasticQuery/blob/master/src/Query/HasChild.php)
+
+```php
+new \Spameri\ElasticQuery\Query\HasChild(
+	type: 'comment',
+	query: new \Spameri\ElasticQuery\Query\Term('author', 'john'),
+	scoreMode: 'max',
+	minChildren: 1,
+);
+```
+
+---
+
 ## Specialized Queries
 
 ##### MatchAll Query

src/Query/HasChild.php

@@ -0,0 +1,62 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace Spameri\ElasticQuery\Query;
+
+/**
+ * @see https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-has-child-query.html
+ */
+class HasChild implements \Spameri\ElasticQuery\Query\LeafQueryInterface
+{
+
+	public function __construct(
+		private string $type,
+		private \Spameri\ElasticQuery\Query\LeafQueryInterface $query,
+		private string|null $scoreMode = null,
+		private int|null $minChildren = null,
+		private int|null $maxChildren = null,
+		private bool|null $ignoreUnmapped = null,
+	)
+	{
+	}
+
+
+	public function key(): string
+	{
+		return 'has_child_' . $this->type;
+	}
+
+
+	/**
+	 * @return array<string, array<string, mixed>>
+	 */
+	public function toArray(): array
+	{
+		$body = [
+			'type' => $this->type,
+			'query' => $this->query->toArray(),
+		];
+
+		if ($this->scoreMode !== null) {
+			$body['score_mode'] = $this->scoreMode;
+		}
+
+		if ($this->minChildren !== null) {
+			$body['min_children'] = $this->minChildren;
+		}
+
+		if ($this->maxChildren !== null) {
+			$body['max_children'] = $this->maxChildren;
+		}
+
+		if ($this->ignoreUnmapped !== null) {
+			$body['ignore_unmapped'] = $this->ignoreUnmapped;
+		}
+
+		return [
+			'has_child' => $body,
+		];
+	}
+
+}

tests/SpameriTests/ElasticQuery/Query/HasChild.phpt

@@ -0,0 +1,67 @@
+<?php declare(strict_types = 1);
+
+namespace SpameriTests\ElasticQuery\Query;
+
+require_once __DIR__ . '/../../bootstrap.php';
+
+
+class HasChild extends \Tester\TestCase
+{
+
+	private const INDEX = 'spameri_test_query_has_child';
+
+
+	public function setUp(): void
+	{
+		$ch = \curl_init();
+		\curl_setopt($ch, \CURLOPT_URL, \ELASTICSEARCH_HOST . '/' . self::INDEX);
+		\curl_setopt($ch, \CURLOPT_RETURNTRANSFER, 1);
+		\curl_setopt($ch, \CURLOPT_CUSTOMREQUEST, 'PUT');
+		\curl_setopt($ch, \CURLOPT_HTTPHEADER, ['Content-Type: application/json']);
+
+		\curl_exec($ch);
+	}
+
+
+	public function testToArray(): void
+	{
+		$hasChild = new \Spameri\ElasticQuery\Query\HasChild(
+			type: 'comment',
+			query: new \Spameri\ElasticQuery\Query\Term('author', 'john'),
+			scoreMode: 'max',
+			minChildren: 1,
+		);
+
+		$array = $hasChild->toArray();
+
+		\Tester\Assert::same('comment', $array['has_child']['type']);
+		\Tester\Assert::same('max', $array['has_child']['score_mode']);
+		\Tester\Assert::same(1, $array['has_child']['min_children']);
+	}
+
+
+	public function testKey(): void
+	{
+		$hasChild = new \Spameri\ElasticQuery\Query\HasChild(
+			'comment',
+			new \Spameri\ElasticQuery\Query\Term('author', 'john'),
+		);
+
+		\Tester\Assert::same('has_child_comment', $hasChild->key());
+	}
+
+
+	public function tearDown(): void
+	{
+		$ch = \curl_init();
+		\curl_setopt($ch, \CURLOPT_URL, \ELASTICSEARCH_HOST . '/' . self::INDEX);
+		\curl_setopt($ch, \CURLOPT_RETURNTRANSFER, 1);
+		\curl_setopt($ch, \CURLOPT_CUSTOMREQUEST, 'DELETE');
+		\curl_setopt($ch, \CURLOPT_HTTPHEADER, ['Content-Type: application/json']);
+
+		\curl_exec($ch);
+	}
+
+}
+
+(new HasChild())->run();