Disabling a quiz question type module leaves quizes with an existing question of that type unusable [#2402535]

Problem/Motivation

When disabling a Quiz question type module, existing Quizzes that use a question of that type are rendered unusable.

When taking the quiz (node/%quiz_menu/take/%question_number):
Fatal error: Call to a member function getAnsweringForm() on a non-object in /[...]/quiz/question_types/quiz_question/quiz_question.module on line 178

When managing questions in a quiz (node/%quiz_menu/quiz/questions):
Fatal error: Call to a member function isGraded() on a non-object in /[...]/quiz/quiz.admin.inc on line 911

To reproduce:

Add a quiz with two question types
Disable the second question type
Take/manage the quiz

Proposed resolution

Option 1 Very fancy version:
Implement hook_node_type_delete() and update every quiz to remove the questions of the node type

Option 2 Less fancy version:
Render a message 'Question is no longer available' when taking/managing a quiz with a missing question.

Remaining tasks

Write a patch
Review

User interface changes

Less fatal errors when taking/managing a quiz with missing questions

API changes

None

Comments

Comment #1

idebr CreditAttribution: idebr commented 6 January 2015 at 13:41

Title:

Disabling a quiz question type module leaves quizes with an existing question of that type unusabe

» Disabling a quiz question type module leaves quizes with an existing question of that type unusable

Comment #2

djdevin

Philadelphia

CreditAttribution: djdevin commented 6 January 2015 at 15:05

We could add a question delete hook, but that might be very destructive considering you may have Quizzes or Quiz results that contain the question type, and it would mess up those results.

I'm for adding error conditions, blocking Quiz taking, and leaving it at that. We could do this by adding a QuizQuestionBroken/QuizQuestionBrokenResponse class then falling back to it. Some other modules do this to handle the fatal errors that would happen from instantiating classes that don't exist, but allowing the site to function.

We can modify _quiz_question_get_instance() and _quiz_question_response_get_instance() to return broken instances that serve as placeholders until the Quiz admin re-enables the question type or deletes the reference.

Some examples:

https://api.drupal.org/api/views/handlers!views_handler_area.inc/class/v...
http://cgit.drupalcode.org/course/tree/includes/course_object.core.inc?i...
http://drupalcontrib.org/api/drupal/contributions!entityreference!plugin...