Content filter: Allowed custom diagram attribute in allow-list

For #6026

Author: ssddanbrown

app/Util/ConfiguredHtmlPurifier.php

@@ -134,6 +134,13 @@ public function configureDefinition(HTMLPurifier_HTMLDefinition $definition): vo
                 'value' => 'Text',
             ]
         );
+
+        // Allow the drawio-diagram attribute on div elements
+        $definition->addAttribute(
+            'div',
+            'drawio-diagram',
+            'Number',
+        );
     }
 
     public function purify(string $html): string

tests/Entity/PageContentFilteringTest.php

@@ -463,6 +463,7 @@ public function test_allow_list_style_filtering()
             '<div style="position:absolute;left:0;color:#00FFEE;">Hello!</div>' => '<div style="color:#00FFEE;">Hello!</div>',
             '<div style="background:#FF0000;left:0;color:#00FFEE;">Hello!</div>' => '<div style="background:#FF0000;color:#00FFEE;">Hello!</div>',
             '<div style="color:#00FFEE;">Hello!<style>testinghello!</style></div>' => '<div style="color:#00FFEE;">Hello!</div>',
+            '<div drawio-diagram="5332" another-attr="cat">Hello!</div>' => '<div drawio-diagram="5332">Hello!</div>',
         ];
 
         config()->set('app.content_filtering', 'a');