Add helper-type for XPath queries

Author: tvdijen

src/XMLSchema/Type/Helper/XPathValue.php

@@ -0,0 +1,30 @@
+<?php
+
+declare(strict_types=1);
+
+namespace SimpleSAML\XMLSchema\Type\Helper;
+
+use DOMNodeList;
+use DOMXPath;
+use SimpleSAML\Assert\Assert;
+use SimpleSAML\XML\DOMDocumentFactory;
+use SimpleSAML\XMLSchema\Type\StringValue;
+
+/**
+ * @package simplesaml/xml-common
+ */
+class XPathValue extends StringValue
+{
+    /**
+     * Validate the content of the element.
+     *
+     * @throws \SimpleSAML\Assert\AssertionFailedException on failure
+     */
+    protected function validateValue(string $content): void
+    {
+        $dom = new DOMXPath(DOMDocumentFactory::create());
+
+        $result = $dom->evaluate($content);
+        Assert::isInstanceOf($result, DOMNodeList::class);
+    }
+}

tests/XMLSchema/Type/Helper/XPathValueTest.php

@@ -0,0 +1,48 @@
+<?php
+
+declare(strict_types=1);
+
+namespace SimpleSAML\Test\XMLSchema\Type\Builtin;
+
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\DataProvider;
+use PHPUnit\Framework\TestCase;
+use SimpleSAML\Assert\AssertionFailedException;
+use SimpleSAML\XMLSchema\Type\Helper\XPathValue;
+
+/**
+ * Class \SimpleSAML\Test\XMLSchema\Type\Helper\XPathValueTest
+ *
+ * @package simplesamlphp/xml-common
+ */
+#[CoversClass(XPathValue::class)]
+final class XPathValueTest extends TestCase
+{
+    /**
+     * @param bool $shouldPass
+     * @param string $xpath
+     */
+    #[DataProvider('provideXPath')]
+    public function testString(bool $shouldPass, string $xpath): void
+    {
+        try {
+            $value = XPathValue::fromString($xpath);
+            $this->assertTrue($shouldPass);
+        } catch (AssertionFailedException $e) {
+            $this->assertFalse($shouldPass);
+        }
+    }
+
+
+    /**
+     * @return array<string, array{0: string, 1: string}>
+     */
+    public static function provideXPath(): array
+    {
+        return [
+            'xpath' => [true, '//h1/following-sibling::ul'],
+            'empty string' => [false, ''],
+            'nonsense' => [false, 'I know nothing'],
+        ];
+    }
+}