feat: add merge_attributes() function to TwigFunctions, make available in twig templates.

Author: Daniel Morse

packages/core-php/src/TwigExtensions/BoltExtras.php

@@ -20,7 +20,8 @@ public function getFunctions() {
       Bolt\TwigFunctions::link(),
       Bolt\TwigFunctions::getSpacingScaleSequence(),
       Bolt\TwigFunctions::github_url(),
-      Bolt\TwigFunctions::inlineFile()
+      Bolt\TwigFunctions::inlineFile(),
+      Bolt\TwigFunctions::merge_attributes()
     ];
   }
 

packages/core-php/src/TwigFunctions.php

@@ -265,6 +265,23 @@ public static function create_attribute() {
     });
   }
 
+  // Custom function for merging Drupal Attribute objects
+  // Gives $source preference, unless a key is set in both arrays and $source value is empty or null
+  public static function merge_attributes() {
+    return new Twig_SimpleFunction('merge_attributes', function($target, $source) {
+      // For each key in $source...
+      foreach ($source as $key => $value) {
+        // If $key is not in $target, or if $key is in $target and $value in $source is empty, add/overwrite $key in $target
+        // NOTE: empty() and is_null() do not work in the second half of this statement. Why is that?
+        if (empty($target[$key]) || (!empty($target[$key]) && $value != "")) {
+          $target[$key] = $value;
+        }
+      }
+
+      return $target;
+    });
+  }
+
   public static function github_url() {
     return new Twig_SimpleFunction('github_url', function(\Twig_Environment $env, $twigPath) {
       $filePath = TwigTools\Utils::resolveTwigPath($env, $twigPath);