Add id suffix generation to radio buttons.

This preserves behavior FormHelper had where it prevents duplicate ids
in a single set of radio options.

src/View/Widget/Radio.php

@@ -40,6 +40,13 @@ class Radio implements WidgetInterface {
  */
 	protected $_label;
 
+/**
+ * A list of id suffixes used in the current rendering.
+ *
+ * @var array
+ */
+	protected $_idSuffixes = [];
+
 /**
  * Constructor
  *
@@ -97,6 +104,7 @@ public function render(array $data) {
 		}
 		unset($data['empty']);
 
+		$this->_idSuffixes = [];
 		$opts = [];
 		foreach ($options as $val => $text) {
 			$opts[] = $this->_renderInput($val, $text, $data);
@@ -206,6 +214,15 @@ protected function _renderLabel($radio, $label, $input, $escape) {
  * @return string Generated id.
  */
 	protected function _id($radio) {
-		return mb_strtolower(Inflector::slug($radio['name'] . '_' . $radio['value'], '-'));}
+		$value = mb_strtolower(Inflector::slug($radio['name'], '-'));
+		$idSuffix = mb_strtolower(str_replace(array('@', '<', '>', ' ', '"', '\''), '-', $radio['value']));
+		$count = 1;
+		$check = $idSuffix;
+		while (in_array($check, $this->_idSuffixes)) {
+			$check = $idSuffix . $count++;
+		}
+		$this->_idSuffixes[] = $check;
+		return trim($value . '-' . $check, '-');
+	}
 
 }

tests/TestCase/View/Widget/RadioTest.php

@@ -123,6 +123,42 @@ public function testRenderComplex() {
 		$this->assertTags($result, $expected);
 	}
 
+/**
+ * Test that id suffixes are generated to not collide
+ *
+ * @return void
+ */
+	public function testRenderIdSuffixGeneration() {
+		$label = new Label($this->templates);
+		$radio = new Radio($this->templates, $label);
+		$data = [
+			'name' => 'Thing[value]',
+			'options' => ['a>b' => 'First', 'a<b' => 'Second']
+		];
+		$result = $radio->render($data);
+		$expected = [
+			['input' => [
+				'type' => 'radio',
+				'name' => 'Thing[value]',
+				'value' => 'a&gt;b',
+				'id' => 'thing-value-a-b'
+			]],
+			['label' => ['for' => 'thing-value-a-b']],
+			'First',
+			'/label',
+			['input' => [
+				'type' => 'radio',
+				'name' => 'Thing[value]',
+				'value' => 'a&lt;b',
+				'id' => 'thing-value-a-b2',
+			]],
+			['label' => ['for' => 'thing-value-a-b2']],
+			'Second',
+			'/label',
+		];
+		$this->assertTags($result, $expected);
+	}
+
 /**
  * Test rendering the empty option.
  *