empty comments are no longer possible

core/serializers/feedback.py

@@ -163,6 +163,11 @@ class FeedbackSerializer(DynamicFieldsModelSerializer):
 
         for comment in data.get('feedback_lines', {}):
             lines_in_submission = len(submission.text.split('\n'))
+
+            if comment['text'] == '' and 'labels' not in comment:
+                raise serializers.ValidationError(
+                    "Cannot create feedback with an empty comment attached to it"
+                )
             if not 0 < comment['of_line'] <= lines_in_submission:
                 raise serializers.ValidationError(
                     "Cannot comment line number %d of %d" % (

frontend/src/components/submission_notes/base/CommentForm.vue

@@ -104,11 +104,18 @@ export default class CommentForm extends mixins(commentLabelSelector) {
   }
   
   submitFeedback () {
+    const text = this.currentFeedback
+    const labels = this.labelsUnchanged.concat(this.labelsAdded)
+
+    if (text === "" && labels.length === 0) {
+      return this.collapseTextField()
+    }
+
     const payload = {
       lineNo: Number(this.lineNo),
       comment: {
-        text: this.currentFeedback,
-        labels: this.labelsUnchanged.concat(this.labelsAdded),
+        text: text,
+        labels: labels,
       }
     }