fix(features/compose): Handle external changes to the textarea (#3632)

app/javascript/mastodon/features/compose/components/compose_form.js

@@ -67,6 +67,12 @@ export default class ComposeForm extends ImmutablePureComponent {
   }
 
   handleSubmit = () => {
+    if (this.props.text !== this.autosuggestTextarea.textarea.value) {
+      // Something changed the text inside the textarea (e.g. browser extensions like Grammarly)
+      // Update the state to match the current text
+      this.props.onChange(this.autosuggestTextarea.textarea.value);
+    }
+
     this.props.onSubmit();
   }