dataset camel case bugfix (#434)

* test: isolate bug #432

* fix: correct camel case for dataset attributes
closes #432

Author: Greg Bowler

src/DOMStringMap.php

@@ -24,11 +24,13 @@ public function __construct(
 	}
 
 	public function __get(string $name):?string {
+		$name = $this->correctCamelCase($name);
 		$keyValuePairs = call_user_func($this->getterCallback);
 		return $keyValuePairs[$name] ?? null;
 	}
 
 	public function __set(string $name, string $value):void {
+		$name = $this->correctCamelCase($name);
 		$keyValuePairs = call_user_func($this->getterCallback);
 		$keyValuePairs[$name] = $value;
 		call_user_func($this->setterCallback, $keyValuePairs);
@@ -46,4 +48,18 @@ public function count():int {
 		$keyValuePairs = call_user_func($this->getterCallback);
 		return count($keyValuePairs);
 	}
+
+	private function correctCamelCase(string $name):string {
+		preg_match_all(
+			'/((?:^|[A-Z])[a-z]+)/',
+			$name,
+			$matches
+		);
+
+		$wordArray = [];
+		foreach($matches[0] as $word) {
+			array_push($wordArray, lcfirst($word));
+		}
+		return implode("-", $wordArray);
+	}
 }

test/phpunit/DOMStringMapFactoryTest.php

@@ -38,6 +38,19 @@ public function testCreateDatasetWithDataAttribute():void {
 		self::assertEquals("php", $domStringMap->language);
 	}
 
+	public function testSetCorrectsCamelCase():void {
+		$document = new HTMLDocument();
+		$element = $document->createElement("example-element");
+		$domStringMap = DOMStringMapFactory::createDataset($element);
+		self::assertCount(0, $element->attributes);
+		$domStringMap->thisIsCamelCase = "test";
+		self::assertCount(1, $element->attributes);
+		$attribute = $element->attributes[0];
+		self::assertSame("data-this-is-camel-case", $attribute->name);
+		self::assertSame("test", $attribute->value);
+		self::assertSame("test", $element->dataset->thisIsCamelCase);
+	}
+
 	public function testCreateDatasetMutate():void {
 		$attributeArray = [
 			"id" => "example",