Fixed silent failure when constructor not called

- Closed #55

src/DOMDocument.php

@@ -15,6 +15,8 @@
  */
 class DOMDocument extends \DOMDocument
 {
+	private $constructorCalled = false; // NB: Used to signal bad state, otherwise we get silent failure when trying to loadHTML before calling constructor
+
 	const UNDEFINED = "b0814351-6e51-4134-a77b-8e5fbec4e026"; // NB: Used to differentiate between explicit null and argument not supplied, for example in DOMQueryResults::css
 
 	/**
@@ -23,7 +25,8 @@ class DOMDocument extends \DOMDocument
 	public function __construct($version='1.0', $encoding='UTF-8')
 	{
 		\DOMDocument::__construct($version, $encoding);
-
+
+		$this->constructorCalled = true;
 		$this->registerNodeClass('DOMElement', 'PerryRylance\DOMDocument\DOMElement');
 	}
 
@@ -114,6 +117,9 @@ public function shorthand()
 	 */
 	public function loadHTML($src, $options=array())
 	{
+		if(!$this->constructorCalled)
+			throw new \Exception("Bad state (did you try to loadHTML before calling constructor?)");
+
 		if(empty($options))
 			$options = [];
 

tests/DOMDocumentTest.php

@@ -3,6 +3,14 @@
 use PerryRylance\DOMDocument;
 use PHPUnit\Framework\TestCase;
 
+class DOMDocumentBadInit extends DOMDocument
+{
+	public function __construct()
+	{
+		$this->loadHTML("This should throw a bad state exception, because the parent class is not initialized");
+	}
+}
+
 final class DOMDocumentTest extends TestCase
 {
 	private function getDocument()
@@ -385,4 +393,11 @@ public function testShorthandMethod()
 
 		$this->assertTrue( !$failed );
 	}
+
+	public function testCloneNode()
+	{
+		$this->expectException(Exception::class);
+
+		$document = new DOMDocumentBadInit();
+	}
 }