Added os2forms_fordelingskomponent_xml_encode Twig filter

Author: rimi-itk

docs/Users-manual.md

@@ -262,3 +262,28 @@ float value based on a language code:
 {{ os2forms_fordelingskomponent_floatval('1,23', langcode: 'da') == 1.23 }}
 {{ os2forms_fordelingskomponent_floatval('1.23', langcode: 'da') == 123}}
 ```
+
+A Twig filter, `os2forms_fordelingskomponent_xml_encode`, can be used to convert an array value to an XML fragment:
+
+``` twig
+{% set value = {
+  Person: {
+    firstname: 'Lucky',
+    lastname: 'Luke',
+  },
+  Horse: {
+    name: 'Jolly Jumper',
+  },
+} %}
+{{ value|os2forms_fordelingskomponent_xml_encode }}
+```
+
+will render
+
+``` xml
+<Person><firstname>John</firstname><lastname>Doe</lastname></Person><Horse><name>Jolly Jumper</name></Horse>
+```
+
+Notice that `os2forms_fordelingskomponent_xml_encode` is "[safe for
+HTML](https://twig.symfony.com/doc/3.x/advanced.html#automatic-escaping)", i.e. you don't have to use
+[`raw`](https://twig.symfony.com/doc/3.x/filters/raw.html) to render the XML.

src/Os2formsFordelingskomponentTwigExtension.php

@@ -5,6 +5,7 @@
 namespace Drupal\os2forms_fordelingskomponent;
 
 use Twig\Extension\AbstractExtension;
+use Twig\TwigFilter;
 use Twig\TwigFunction;
 
 /**
@@ -46,4 +47,44 @@ static function (string $argument, ?string $langcode = NULL): float {
     return $functions;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  #[\Override]
+  public function getFilters(): array {
+    $filters[] = new TwigFilter(
+      'os2forms_fordelingskomponent_xml_encode',
+      static function (array $value, string $numeric_key_prefix = 'key_'): string {
+        // https://stackoverflow.com/a/19987539
+        $toXml = static function (\SimpleXMLElement $object, array $data) use (&$toXml, $numeric_key_prefix) {
+          foreach ($data as $key => $value) {
+            // If the key is an integer, it needs text with it to actually work.
+            $valid_key  = is_numeric($key) ? $numeric_key_prefix . $key : $key;
+            $new_object = $object->addChild(
+              $valid_key,
+              is_array($value) ? NULL : htmlspecialchars((string) $value)
+            );
+
+            if (is_array($value)) {
+              $toXml($new_object, $value);
+            }
+          }
+        };
+
+        $sxe = new \SimpleXMLElement('<?xml version="1.0" encoding="UTF-8"?><root/>');
+        $toXml($sxe, $value);
+
+        $fragment = '';
+        foreach ($sxe->xpath('/root/*') as $child) {
+          $fragment .= $child->asXML();
+        }
+
+        return $fragment;
+      },
+      ['is_safe' => ['html']]
+    );
+
+    return $filters;
+  }
+
 }