feat: allow attributes string as constructor argument

README.md

@@ -43,8 +43,24 @@ You can also use named arguments if you prefer a leaner syntax. Be aware, that t
 ) ?>>
 ```
 
-⚠️ If you need XML-compatible attributes, always call `$attributes->toXml()` instead of just echoing the `Attributes` object,
-because otherwise all attributes will be converted to lower-case.
+Or if all you have is an attributes string, you can also feed the that to the `attributes()` helper:
+
+```php
+<?php
+
+// get image dimensions as height="yyy" width="xxx" 
+$src  = 'img.png';
+$size = getimagesize($src)[3];
+
+?>
+
+<img <?= attributes($size)->merge([
+	'src' => $src,
+	'alt' => '',
+]) ?>>
+```
+
+⚠️ If you need XML-compatible attributes, always call `$attributes->toXml()` instead of just echoing the `Attributes` object, because otherwise all attributes will be converted to lower-case.
 
 In many cases, you need to set different classes. The `classes()` helper is a nice shortcut for improved readability:
 

src/Attributes.php

@@ -3,6 +3,7 @@
 namespace FabianMichael\TemplateAttributes;
 
 use ArrayAccess;
+use DOMDocument;
 use Exception;
 use Kirby\Toolkit\A;
 use Kirby\Toolkit\Html;
@@ -19,6 +20,38 @@ class Attributes implements ArrayAccess, Stringable
 	protected ?string $before = null;
 	protected ?string $after = null;
 
+	// see https://html.spec.whatwg.org/multipage/indices.html#attributes-3
+	public static array $booleanAttributes = [
+		'allowfullscreen',
+		'async',
+		'autofocus',
+		'autoplay',
+		'checked',
+		'controls',
+		'default',
+		'defer',
+		'disabled',
+		'formnovalidate',
+		'hidden', // not a boolean attribute, but can be used like one
+		'inert',
+		'ismap',
+		'itemscope',
+		'loop',
+		'multiple',
+		'muted',
+		'nomodule',
+		'novalidate',
+		'open',
+		'playsinline',
+		'readonly',
+		'required',
+		'reversed',
+		'selected',
+		'shadowrootclonable',
+		'shadowrootdelegatesfocus',
+		'shadowrootserializable',
+	];
+
 	public function __construct(...$data)
 	{
 		$this->merge(...$data);
@@ -81,14 +114,19 @@ public function get(?string $name = null): AttributeValue|array|null
 	public function merge(...$data): static
 	{
 		if (count($data) === 1 && array_key_first($data) === 0) {
-			// Single array/object input
+			// single array/object input
 			$data = $data[0];
 		}
 
 		if (is_a($data, self::class)) {
+			// argument was another instance of Attributes
 			$data = $data->data;
 		}
 
+		if (is_string($data)) {
+			$data = static::parseAttributesString($data);
+		}
+
 		foreach ($data as $name => $value) {
 			$this->set($name, $value);
 		}
@@ -236,4 +274,32 @@ public function __toString(): string
 	{
 		return $this->toHtml() ?? '';
 	}
+
+	protected static function parseAttributesString(string $str): array
+	{
+		$tagName = 'yolo';
+		$errorsBefore = libxml_use_internal_errors();
+		$attr = [];
+
+		libxml_use_internal_errors(true);
+		$dom = new DOMDocument();
+		$dom->loadHTML("<{$tagName} {$str}>");
+		$node = $dom->getElementsByTagName($tagName)->item(0);
+		if ($node->hasAttributes()) {
+			foreach ($node->attributes as $attribute) {
+				$name = $attribute->nodeName;
+				$value = $attribute->nodeValue;
+
+				if (in_array($value, ['', $name]) && in_array($name, static::$booleanAttributes)) {
+					// convert known boolean attributes to bool
+					$value = true;
+				}
+
+				$attr[$name] = $value;
+			}
+		}
+
+		libxml_use_internal_errors($errorsBefore);
+		return $attr;
+	}
 }

tests/AttributesTest.php

@@ -19,6 +19,15 @@ public function testConstructorArray(): void
 		$this->assertSame((string) $attr, 'bar="foo" foo="bar"');
 	}
 
+	public function testConstructorSingleNamedArgument(): void
+	{
+		$attr = new Attributes(
+			bar: 'foo',
+		);
+
+		$this->assertSame((string) $attr, 'bar="foo"');
+	}
+
 	public function testConstrucorNamedArguments(): void
 	{
 		$attr = new Attributes(
@@ -29,6 +38,20 @@ public function testConstrucorNamedArguments(): void
 		$this->assertSame((string) $attr, 'bar="foo" foo="bar"');
 	}
 
+	public function testConstructFromAttributesString(): void
+	{
+		$attr = new Attributes('foo="bar" bar="foo"');
+
+		$this->assertSame((string) $attr, 'bar="foo" foo="bar"');
+	}
+
+	public function testConstructFromAttributesStringWithBooleanAttributes(): void
+	{
+		$attr = new Attributes('novalidate inert unknown-boolean');
+
+		$this->assertSame((string) $attr, 'inert novalidate unknown-boolean=""');
+	}
+
 	public function testConversionToLowerCase(): void
 	{
 		$attr = new Attributes(