Fix missing feedback after manual regrade

renderer.php

@@ -867,13 +867,20 @@ public function part_correct_response($part) {
     /**
      * Check whether the last response of a question attempt is the same as the last submitted response, i. e. it
      * was either submitted (e. g. using the "Check" button) or it was saved during page navigation in a quiz but
-     * still contains the same answers as the ones from the last regular submission.
+     * still contains the same answers as the ones from the last regular submission. This is used to decide whether
+     * the feedback should be shown or not.
      *
      * @param question_attempt $qa
      * @param formulas_part|null $part
      * @return bool
      */
     protected function response_is_same_as_submitted(question_attempt $qa, formulas_part|null $part = null): bool {
+        // If the question is marked as finished, we will return true here to make sure the feedback
+        // will be shown, because students will not be able to interact with the question anymore.
+        if ($qa->get_state()->is_finished()) {
+            return true;
+        }
+
         // If the last step contains the behaviour var 'submit', it was itself a submitted response.
         // For the deferredfeedback behaviour, the step will contain 'finish' instead of 'submit'.
         $laststep = $qa->get_last_step();

tests/renderer_test.php

@@ -121,6 +121,36 @@ public function test_show_response_with_backslash(): void {
         $this->check_output_contains_text_input('0_0', '\1', false);
     }
 
+    public function test_feedback_remains_visible_after_manual_regrading(): void {
+        $q = $this->get_test_formulas_question('testthreeparts');
+        $this->start_attempt_at_question($q, 'deferredfeedback', 3);
+
+        // Submit wrong answer.
+        $this->process_submission(['0_0' => '1', '1_0' => '6', '2_0' => '7']);
+        $this->finish();
+        $this->render();
+        $this->check_current_state(question_state::$gradedpartial);
+        $this->check_output_contains_lang_string('correctansweris', 'qtype_formulas', '5');
+        $this->check_output_contains_lang_string('correctansweris', 'qtype_formulas', '6');
+        $this->check_output_contains_lang_string('correctansweris', 'qtype_formulas', '7');
+        $this->check_current_output(
+            $this->get_contains_num_parts_correct(2),
+        );
+
+        // Manually regrade the question and add a comment.
+        $this->quba->manual_grade(1, 'giving some bonus', 2.5, FORMAT_HTML);
+
+        $this->render();
+        $this->check_current_state(question_state::$mangrpartial);
+        $this->check_output_contains_lang_string('correctansweris', 'qtype_formulas', '5');
+        $this->check_output_contains_lang_string('correctansweris', 'qtype_formulas', '6');
+        $this->check_output_contains_lang_string('correctansweris', 'qtype_formulas', '7');
+        $this->check_output_contains('giving some bonus');
+        $this->check_current_output(
+            $this->get_contains_num_parts_correct(2),
+        );
+    }
+
     public function test_adaptive_grading_details_are_shown(): void {
         // Create a simple test question with no feedback strings at all.
         $q = $this->get_test_formulas_question('testsinglenum');