Prevent duplication of editor content

By removing the content once added to the ACE editor, we prevent an issue with Turbolinks / Turbo duplicating the lines. This issue became apparent during the migration to Turbo, since its behavior changed in comparison to Turbolinks.

See hotwired/turbo#1413

Author: MrSerth

app/assets/javascripts/editor.js

@@ -14,9 +14,6 @@ $(document).on('turbolinks:load', function(event) {
   );
 
   if ($('#editor').isPresent() && CodeOceanEditor && event.originalEvent.data.url.includes("/implement")) {
-    // This call will (amon other things) initializeEditors and load the content except for the last line
-    // It must not be called during page navigation. Otherwise, content will be duplicated!
-    // Search for insertFullLines and Turbolinks reload / cache control
     CodeOceanEditor.initializeEverything();
   }
 

app/assets/javascripts/editor/editor.js.erb

@@ -286,9 +286,15 @@ var CodeOceanEditor = {
             var content = $('.editor-content[data-file-id=' + file_id + ']');
             this.setActiveFile($(element).parent().data('filename'), file_id);
 
-            document.insertFullLines(0, content.text().split(/\n/));
-            // remove last (empty) that is there by default line
-            document.removeFullLines(document.getLength() - 1, document.getLength() - 1);
+            const full_lines = content.text().split(/\n/);
+            if (full_lines.length > 1 && full_lines[0] !== "") {
+                document.insertFullLines(0, full_lines);
+                // remove last (empty) that is there by default line
+                document.removeFullLines(document.getLength() - 1, document.getLength() - 1);
+                // remove content from DOM, so that it won't be readded during Turbo navigation
+                content.text("");
+            }
+
             editor.setReadOnly($(element).parent().data('read-only') !== undefined);
             if (editor.getReadOnly()) {
                 editor.setHighlightActiveLine(false);