MDL-43733 use any auto-saved responses when questions are finished.

Before this, autosave was only working to save data when a student went
back in to continue an attempt. If the student, having crashed out,
never went back in and continued the attempt, their auto-saved responses
were not used when the attempt was automatically finished. That was a
rather bad oversight, which should now be fixed.

question/engine/questionattempt.php

@@ -869,6 +869,24 @@ public function discard_autosaved_step() {
         $this->observer->notify_step_deleted($autosaved, $this);
     }
 
+    /**
+     * If there is an autosaved step, convert it into a real save, so that it
+     * is preserved.
+     */
+    protected function convert_autosaved_step_to_real_step() {
+        if ($this->autosavedstep === null) {
+            return;
+        }
+
+        $laststep = end($this->steps);
+        if ($laststep !== $this->autosavedstep) {
+            throw new coding_exception('Cannot convert autosaved step to real step, since other steps have been added.');
+        }
+
+        $this->observer->notify_step_modified($this->autosavedstep, $this, key($this->steps));
+        $this->autosavedstep = null;
+    }
+
     /**
      * Use a strategy to pick a variant.
      * @param question_variant_selection_strategy $variantstrategy a strategy.
@@ -1174,6 +1192,7 @@ public function process_autosave($submitteddata, $timestamp = null, $userid = nu
      * @param int $userid the user to attribute the aciton to. (If not given, use the current user.)
      */
     public function finish($timestamp = null, $userid = null) {
+        $this->convert_autosaved_step_to_real_step();
         $this->process_action(array('-finish' => 1), $timestamp, $userid);
     }
 

question/engine/tests/questionusage_autosave_test.php

@@ -628,4 +628,61 @@ public function test_autosave_with_wrong_seq_number_ignored() {
 
         $this->delete_quba();
     }
+
+    public function test_finish_with_unhandled_autosave_data() {
+        $this->resetAfterTest();
+        $generator = $this->getDataGenerator()->get_plugin_generator('core_question');
+        $cat = $generator->create_question_category();
+        $question = $generator->create_question('shortanswer', null,
+                array('category' => $cat->id));
+
+        // Start attempt at a shortanswer question.
+        $q = question_bank::load_question($question->id);
+        $this->start_attempt_at_question($q, 'deferredfeedback', 1);
+
+        $this->check_current_state(question_state::$todo);
+        $this->check_current_mark(null);
+        $this->check_step_count(1);
+
+        // Process a response and check the expected result.
+        $this->process_submission(array('answer' => 'cat'));
+
+        $this->check_current_state(question_state::$complete);
+        $this->check_current_mark(null);
+        $this->check_step_count(2);
+        $this->save_quba();
+
+        // Now check how that is re-displayed.
+        $this->render();
+        $this->check_output_contains_text_input('answer', 'cat');
+        $this->check_output_contains_hidden_input(':sequencecheck', 2);
+
+        // Process an autosave.
+        $this->load_quba();
+        $this->process_autosave(array('answer' => 'frog'));
+        $this->check_current_state(question_state::$complete);
+        $this->check_current_mark(null);
+        $this->check_step_count(3);
+        $this->save_quba();
+
+        // Now check how that is re-displayed.
+        $this->load_quba();
+        $this->render();
+        $this->check_output_contains_text_input('answer', 'frog');
+        $this->check_output_contains_hidden_input(':sequencecheck', 2);
+
+        // Now finishe the attempt, without having done anything since the autosave.
+        $this->finish();
+        $this->save_quba();
+
+        // Now check how that has been graded and is re-displayed.
+        $this->load_quba();
+        $this->check_current_state(question_state::$gradedright);
+        $this->check_current_mark(1);
+        $this->render();
+        $this->check_output_contains_text_input('answer', 'frog', false);
+        $this->check_output_contains_hidden_input(':sequencecheck', 4);
+
+        $this->delete_quba();
+    }
 }