[MDL-53351] lti_delete_instance() tries to get property of non-object - Moodle Tracker

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Affected Branches:
MOODLE_30_STABLE
Fixed Branches:
MOODLE_29_STABLE, MOODLE_30_STABLE
Pull from Repository:
git://github.com/mudrd8mz/moodle.git
Pull Master Branch:
~~MDL-53351~~-master-lti-notice
Pull Master Diff URL:
https://github.com/mudrd8mz/moodle/compare/7adc7ef...MDL-53351-master-lti-notice
Testing Instructions:
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Shorter: Testing not needed, the fix is covered by a unit test.

Longer:

Add a new instance of the External tool (LTI) to a course, use default settings (in fact, only name is needed).

Delete the instance and make sure no PHP notice is thrown. This means either

avoid deleting via AJAX, e.g. by opening the "Delete" action link in a new tab or having javascript disabled

or watching the server's error_log.
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Shorter: Testing not needed, the fix is covered by a unit test. Longer: Add a new instance of the External tool (LTI) to a course, use default settings (in fact, only name is needed). Delete the instance and make sure no PHP notice is thrown. This means either avoid deleting via AJAX, e.g. by opening the "Delete" action link in a new tab or having javascript disabled or watching the server's error_log.

I found that when a mod_lti instance is being deleted, it throws a PHP notice:

PHP Notice:  Trying to get property of non-object in mod/lti/lib.php on line 192

I found that it is caused by the lti_delete_instance() code doing

    $ltitype = $DB->get_record('lti_types', array('id' => $basiclti->typeid));

    $DB->delete_records('lti_tool_settings',

        array('toolproxyid' => $ltitype->toolproxyid, 'course' => $basiclti->course, 'coursemoduleid' => $id));

without checking that $ltitype actually found the record.

Note that typeid=0 is a valid and common value representing "Automatic, based on launch URL".

Discovered while testing

MDLSITE-3860 Error when attempting to delete large number of courses

Participants:: Andrew Lyons, cameron1729, CiBoT, David Mudrák (@mudrd8mz), Eloy Lafuente (stronk7), John Okely

Component watchers:: Jake Dallimore, Ilya Tregubov, Kevin Percy, Mathew May, Mihail Geshoski, Shamim Rezaie