Make attribute formatting part of StringTemplate

Since attributes are basically string templates with a tiny bit of logic it felt
that these methods would belong here. In the long term I hope to remove them from
Helper and have Helper use these methods instead.

Cake/View/StringTemplate.php

@@ -27,12 +27,26 @@
  */
 class StringTemplate {
 
+/**
+ * List of attributes that can be made compact.
+ *
+ * @var array
+ */
+	protected $_compactAttributes = array(
+		'compact', 'checked', 'declare', 'readonly', 'disabled', 'selected',
+		'defer', 'ismap', 'nohref', 'noshade', 'nowrap', 'multiple', 'noresize',
+		'autoplay', 'controls', 'loop', 'muted', 'required', 'novalidate', 'formnovalidate'
+	);
+
 /**
  * The templates this instance holds.
  *
  * @var array
  */
-	protected $_templates = [];
+	protected $_templates = [
+		'attribute' => '{{name}}="{{value}}"',
+		'compactAttribute' => '{{name}}="{{value}}"',
+	];
 
 /**
  * Load a config file containing templates.
@@ -111,4 +125,88 @@ public function format($name, array $data) {
 		return strtr($template, $replace);
 	}
 
+/**
+ * Returns a space-delimited string with items of the $options array. If a key
+ * of $options array happens to be one of those listed
+ * in `StringTemplate::$_compactAttributes` and its value is one of:
+ *
+ * - '1' (string)
+ * - 1 (integer)
+ * - true (boolean)
+ * - 'true' (string)
+ *
+ * Then the value will be reset to be identical with key's name.
+ * If the value is not one of these 4, the parameter is not output.
+ *
+ * 'escape' is a special option in that it controls the conversion of
+ * attributes to their html-entity encoded equivalents. Set to false to disable html-encoding.
+ *
+ * If value for any option key is set to `null` or `false`, that option will be excluded from output.
+ *
+ * This method uses the 'attribute' and 'compactAttribute' templates. Each of
+ * these templates uses the `name` and `value` variables. You can modify these
+ * templates to change how attributes are formatted.
+ *
+ * @param array $options Array of options.
+ * @param array $exclude Array of options to be excluded, the options here will not be part of the return.
+ * @param string $insertBefore String to be inserted before options.
+ * @return string Composed attributes.
+ */
+	public function formatAttributes($options, $exclude = null) {
+		$insertBefore = ' ';
+		$options = (array)$options + ['escape' => true];
+
+		if (!is_array($exclude)) {
+			$exclude = [];
+		}
+
+		$exclude = ['escape' => true] + array_flip($exclude);
+		$escape = $options['escape'];
+		$attributes = [];
+
+		foreach ($options as $key => $value) {
+			if (!isset($exclude[$key]) && $value !== false && $value !== null) {
+				$attributes[] = $this->_formatAttribute($key, $value, $escape);
+			}
+		}
+		$out = trim(implode(' ', $attributes));
+		return $out ? $insertBefore . $out : '';
+	}
+
+/**
+ * Formats an individual attribute, and returns the string value of the composed attribute.
+ * Works with minimized attributes that have the same value as their name such as 'disabled' and 'checked'
+ *
+ * @param string $key The name of the attribute to create
+ * @param string $value The value of the attribute to create.
+ * @param boolean $escape Define if the value must be escaped
+ * @return string The composed attribute.
+ */
+	protected function _formatAttribute($key, $value, $escape = true) {
+		if (is_array($value)) {
+			$value = implode(' ', $value);
+		}
+		if (is_numeric($key)) {
+			return $this->format('compactAttribute', [
+				'name' => $value,
+				'value' => $value
+			]);
+		}
+		$truthy = [1, '1', true, 'true', $key];
+		$isMinimized = in_array($key, $this->_compactAttributes);
+		if ($isMinimized && in_array($value, $truthy, true)) {
+			return $this->format('compactAttribute', [
+				'name' => $key,
+				'value' => $key
+			]);
+		}
+		if ($isMinimized) {
+			return '';
+		}
+		return $this->format('attribute', [
+			'name' => $key,
+			'value' => $escape ? h($value) : $value
+		]);
+	}
+
 }

Test/TestCase/View/StringTemplateTest.php

@@ -86,6 +86,8 @@ public function testFormat() {
  * @return void
  */
 	public function testLoad() {
+		$this->template->remove('attribute');
+		$this->template->remove('compactAttribute');
 		$this->assertEquals([], $this->template->get());
 		$this->assertNull($this->template->load('test_templates'));
 		$this->assertEquals('<a href="{{url}}">{{text}}</a>', $this->template->get('link'));
@@ -112,4 +114,67 @@ public function testLoadErrorNoFile() {
 		$this->template->load('no_such_file');
 	}
 
+/**
+ * Test formatting compact attributes.
+ *
+ * @return void
+ */
+	public function testFormatAttributesCompact() {
+		$attrs = ['disabled' => true, 'selected' => 1, 'checked' => '1', 'multiple' => 'multiple'];
+		$result = $this->template->formatAttributes($attrs);
+		$this->assertEquals(
+			' disabled="disabled" selected="selected" checked="checked" multiple="multiple"',
+			$result
+		);
+
+		$attrs = ['disabled' => false, 'selected' => 0, 'checked' => '0', 'multiple' => null];
+		$result = $this->template->formatAttributes($attrs);
+		$this->assertEquals(
+			'',
+			$result
+		);
+	}
+
+/**
+ * Test formatting normal attributes.
+ *
+ * @return void
+ */
+	public function testFormatAttributes() {
+		$attrs = ['name' => 'bruce', 'data-hero' => '<batman>'];
+		$result = $this->template->formatAttributes($attrs);
+		$this->assertEquals(
+			' name="bruce" data-hero="&lt;batman&gt;"',
+			$result
+		);
+
+		$attrs = ['escape' => false, 'name' => 'bruce', 'data-hero' => '<batman>'];
+		$result = $this->template->formatAttributes($attrs);
+		$this->assertEquals(
+			' name="bruce" data-hero="<batman>"',
+			$result
+		);
+
+		$attrs = ['name' => 'bruce', 'data-hero' => '<batman>'];
+		$result = $this->template->formatAttributes($attrs, ['name']);
+		$this->assertEquals(
+			' data-hero="&lt;batman&gt;"',
+			$result
+		);
+	}
+
+/**
+ * Test formatting array attributes.
+ *
+ * @return void
+ */
+	public function testFormatAttributesArray() {
+		$attrs = ['name' => ['bruce', 'wayne']];
+		$result = $this->template->formatAttributes($attrs);
+		$this->assertEquals(
+			' name="bruce wayne"',
+			$result
+		);
+	}
+
 }