FIX Add 'legal empty attributes' to allow empty alt values on i… (#9257)

FIX Add 'legal empty attributes' to allow empty alt values on imgs

src/View/HTML.php

@@ -39,6 +39,16 @@ class HTML
         'wbr'
     ];
 
+    /**
+     * List of attributes that should be rendered even if they contain no value
+     *
+     * @config
+     * @var array
+     */
+    private static $legal_empty_attributes = [
+        'alt',
+    ];
+
     /**
      * Construct and return HTML tag.
      *
@@ -52,10 +62,13 @@ class HTML
         $tag = strtolower($tag);
 
         // Build list of arguments
+        $legalEmptyAttributes = static::config()->get('legal_empty_attributes');
         $preparedAttributes = '';
         foreach ($attributes as $attributeKey => $attributeValue) {
+            $whitelisted = in_array($attributeKey, $legalEmptyAttributes);
+
             // Only set non-empty strings (ensures strlen(0) > 0)
-            if (strlen($attributeValue) > 0) {
+            if (strlen($attributeValue) > 0 || $whitelisted) {
                 $preparedAttributes .= sprintf(
                     ' %s="%s"',
                     $attributeKey,

tests/php/View/HTMLTest.php

@@ -45,6 +45,16 @@ class HTMLTest extends SapphireTest
         $this->assertEquals('<a title="HTML &amp; Text">Some <strong>content!</strong></a>', $tag);
     }
 
+    public function testImgTag()
+    {
+        $tag = HTML::createTag('img', [
+            'src' => 'example.png',
+            'alt' => '',
+        ]);
+
+        $this->assertEquals('<img src="example.png" alt="" />', $tag);
+    }
+
     public function testVoidContentError()
     {
         $this->expectException(InvalidArgumentException::class);