unhelpful error page if a problem in a test has an error

[Alex-Jordan]

An instructor had a test with two questions, one per page. A student was taking this quiz, and it so happened that their random version on the second question had code in it that caused division by zero. When the student (or anyone acting as the student) attempts to go to the second page, there is an error about an answer hash not existing, but it's pretty indecipherable to most users.

[drgrice1]

I think that you might need to provide more details of the problem and the actual error if we are going to be able to diagnose this situation. I tried creating a problem with a custom checker that had an intentional division by zero in it. After grading the test, and then returning to the test later and going to that page, I see a warning at the bottom of the page that an error occurred while grading the problem, and in the feedback button the message says An error occurred while checking your answer: Illegal division by zero at line 9 of local/setTesting/test.pg. That seems rather informative to me. So if you are not seeing that, then there is some other kind of error occurring, and as stated, more information is needed.

[Alex-Jordan]

Don't put the division by zero in a checker. Just put $x = 1/0; in the code for the exercise that will be executed as the problem renders. This is basically what happened for the student, except the 0 was a random variable.

So the problem just won't render, as opposed to hitting an error during the answer checking.

[Alex-Jordan]

Here is the error message the user gets under those conditions, when they try to visit the second page.

Error messages

Can't use an undefined value as a HASH reference at /opt/webwork/webwork2/lib/WeBWorK/Utils/ProblemProcessing.pm line 301.
Context

296: 	my $needsGrading = '';

297: 	my %answers_to_store;

298: 	my @past_answers_order;

299: 	my @last_answer_order;

300: 

301: 	my %pg_answers_hash = %{ $pg->{PG_ANSWERS_HASH} };

302: 	for my $ans_id (@{ $pg->{flags}{ANSWER_ENTRY_ORDER} // [] }) {

303: 		$scores_string .= ($pg_answers_hash{$ans_id}{rh_ans}{score} // 0) >= 1 ? '1' : '0';

304: 		push @answerTypes, $pg_answers_hash{$ans_id}{rh_ans}{type} // '';

305: 		for my $response_id (@{ $pg_answers_hash{$ans_id}{response_obj}{response_order} }) {

306: 			$answers_to_store{$response_id} = $formFields->{$response_id};

[drgrice1]

I see the error now when I am the student. However, if I go to the test when acting as that student, I get a more informative message. I get ERRORS from evaluating PG file: Illegal division by zero at line 5 of local/setTesting/test.pg.

[drgrice1]

There is a rather easy fix so that the student also sees the correct error. Just change line 301 of lib/WeBWorK/Utils/ProblemProcessing.pm from my %pg_answers_hash = %{ $pg->{PG_ANSWERS_HASH} }; to my %pg_answers_hash = %{ $pg->{PG_ANSWERS_HASH} // {} };.

However, it would be even better if the gateway quiz page would still show the problem navigation so that the student can go to other problems at least without having to use the back button. That is probably how this has always been though.