add description in source code

addon/components/bs-form/element.js

@@ -7,6 +7,13 @@ export default BsFormElement.extend({
   hasValidator: notEmpty('model.validate'),
 
   setupValidations() {
+    // `Changeset.error` is a getter based on a tracked property. Since it's a
+    // derived state it's not working together with computed properties smoothly.
+    // As a work-a-round we observe the `Changeset._errors` computed property
+    // directly, which holds the state. This is not optimal cause it's private.
+    // Should refactor to native getter as soon as `<FormElement>` component
+    // of Ember Bootstrap supports native getters for `FormElement.errors`
+    // property.
     let key = `model.error.${this.get('property')}.validation`;
     defineProperty(this, 'errors', computed(`model._errors`, function() {
       return A(this.get(key));