[DomCrawler] Add support for XPath expression evaluation

src/Symfony/Component/DomCrawler/Crawler.php

@@ -592,6 +592,36 @@ public function html()
         return $html;
     }
 
+    /**
+     * Evaluates an XPath expression.
+     *
+     * Since an XPath expression might evaluate to either a simple type or a \DOMDoneList,
+     * this method will return either an array of simple types or a new Crawler instance.
+     *
+     * @param string $xpath An XPath expression
+     *
+     * @return array|Crawler An array of evaluation results or a new Crawler instance
+     */
+    public function evaluate($xpath)
+    {
+        if (null === $this->document) {
+            throw new \LogicException('Cannot evaluate the expression on an uninitialized crawler.');
+        }
+
+        $data = array();
+        $domxpath = $this->createDOMXPath($this->document, $this->findNamespacePrefixes($xpath));
+
+        foreach ($this->nodes as $node) {
+            $data[] = $domxpath->evaluate($xpath, $node);
+        }
+
+        if (isset($data[0]) && $data[0] instanceof \DOMNodeList) {
+            return $this->createSubCrawler($data);
+        }
+
+        return $data;
+    }
+
     /**
      * Extracts information from the list of nodes.
      *

src/Symfony/Component/DomCrawler/Tests/CrawlerTest.php

@@ -1061,6 +1061,51 @@ public function testCountOfNestedElements()
         $this->assertCount(1, $crawler->filter('li:contains("List item 1")'));
     }
 
+    public function testEvaluateReturnsTypedResultOfXPathExpressionOnADocumentSubset()
+    {
+        $crawler = $this->createTestCrawler();
+
+        $result = $crawler->filterXPath('//form/input')->evaluate('substring-before(@name, "Name")');
+
+        $this->assertSame(array('Text', 'Foo', 'Bar'), $result);
+    }
+
+    public function testEvaluateReturnsTypedResultOfNamespacedXPathExpressionOnADocumentSubset()
+    {
+        $crawler = $this->createTestXmlCrawler();
+
+        $result = $crawler->filterXPath('//yt:accessControl/@action')->evaluate('string(.)');
+
+        $this->assertSame(array('comment', 'videoRespond'), $result);
+    }
+
+    public function testEvaluateReturnsTypedResultOfNamespacedXPathExpression()
+    {
+        $crawler = $this->createTestXmlCrawler();
+        $crawler->registerNamespace('youtube', 'http://gdata.youtube.com/schemas/2007');
+
+        $result = $crawler->evaluate('string(//youtube:accessControl/@action)');
+
+        $this->assertSame(array('comment'), $result);
+    }
+
+    public function testEvaluateReturnsACrawlerIfXPathExpressionEvaluatesToANode()
+    {
+        $crawler = $this->createTestCrawler()->evaluate('//form/input[1]');
+
+        $this->assertInstanceOf(Crawler::class, $crawler);
+        $this->assertCount(1, $crawler);
+        $this->assertSame('input', $crawler->first()->nodeName());
+    }
+
+    /**
+     * @expectedException \LogicException
+     */
+    public function testEvaluateThrowsAnExceptionIfDocumentIsEmpty()
+    {
+        (new Crawler())->evaluate('//form/input[1]');
+    }
+
     public function createTestCrawler($uri = null)
     {
         $dom = new \DOMDocument();