[drgrice1]

If a test submission is slow (for example on a bad connection), then the student can submit the test again while the first submission is still being graded. Since the number of attempts is not saved until grading is complete, both submissions were graded as the same attempt, and the one that finished last overwrote the scores of the other. This happened even for tests that allow only one submission per version.

The gateway form now only allows one submission. On the server, the version_last_attempt_time and number of attempts used when the page was rendered are included in the form. A submission is not graded if the number of attempts has changed. Otherwise the submission time is saved with a conditional database update that only succeeds if version_last_attempt_time is unchanged (the new value is always later than the old one, so that two submissions can not both succeed). The proctor login page saves the time in the same way and forwards the new value. Finally, before any scores are saved, the new number of attempts for one problem is saved with a conditional database update that only succeeds if that number is unchanged. That catches a submission from a page rendered while another submission was being graded.

To reproduce the issues, make a test with the following problem and at least one other problem, set "Graded submissions per version" to 1 (except as noted), and assign it to a student. Grading the problem takes 10 seconds, which leaves time to submit again during grading.

DOCUMENT();
loadMacros('PGstandard.pl', 'PGML.pl');

if ($inputs_ref->{submitAnswers}) {
    my $start = time;
    1 while time - $start < 10;
}

BEGIN_PGML
What is [`1 + 1`]? [_]{2}
END_PGML
ENDDOCUMENT();

In each case below, before this change both submissions are recorded and the last to finish overwrites the scores of the other. With this change only the first submission is recorded.

1. Answer all problems, click "Grade Test" and "Yes", and then click "Grade Test" again within 10 seconds.

2. Set the test to show one problem per page. Answer the first problem, click "Next Problem", answer the second problem, and click "Grade Test" on that page. Within 10 seconds, click the back button and click "Grade Test" again. The page that the back button returns to does not have the answer to the second problem, so before this change that answer is lost and the problem is scored as unanswered (the answer log shows both submissions). Grading an older copy of the test that is open in another tab is the same.

3. Answer all problems, grade the test, reload the page (F5) within 10 seconds, change an answer, and grade the test again.

4. With "Graded submissions per version" set to 2, repeat 2 but wait for the results before clicking the back button. Before this change, the submission from the old page is graded as the second attempt. With this change it is not graded.

5. Change the test to a proctored test that requires proctor authorization to grade, and repeat 1 and 2, authorizing each submission with a proctor account. Also click the proctor login button twice for one submission. Only one submission is graded.

Co-Authored-By: Claude Opus 5.5 noreply@anthropic.com