Intermittent error "Call to a member function StartTrans() on a non-object" when saving a blog post in 15.04

[Aaron Wells]

See https://mahara.org/interaction/forum/topic.php?id=7397
Also https://bugs.launchpad.net/mahara/+bug/1513710

The Embedded Image code ( https://reviews.mahara.org/#/c/5128/ ) adds a line to blog/post.php that does "set()" on an artefact without subsequently calling "commit()". This causes the (buggy) artefact destructor method to try to save the object to the database when the script ends, and that can cause an intermittent fatal error if $db got garbage collected before the artefact destructor was called.

[Aaron Wells (u-aaronw)]

This appears to be an intermittent or at least platform-specific problem. But if you were going to try to replicate it, these would be the steps:

1. Create a blog post.
2. Save the blog post.
3. Open the blog post back up for editing.
4. Make a change to the blog post.
5. Save the blog post again.

If you use xdebug or another debugging tool, you can see that on that second save attempt, at least one ArtefactTypeBlogPost object will get its destructor called while $this->dirty is true, causing a database commit to happen during the destructor call.

[Mahara Bot (dev-mahara)]

Patch for "master" branch: https://reviews.mahara.org/5666

[Mahara Bot (dev-mahara)]

Reviewed: https://reviews.mahara.org/5666
Committed: https://git.mahara.org/mahara/mahara/commit/294fa9a4edc5580cdc7a1c3c0c021e2f4b562884
Submitter: Robert Lyon (<email address hidden>)
Branch: master

commit 294fa9a4edc5580cdc7a1c3c0c021e2f4b562884
Author: Aaron Wells <email address hidden>
Date: Fri Nov 6 18:55:40 2015 +1300

Explicitly commit artefact to avoid buggy destructor (Bug 1513716)

Since this blog post object wasn't committed after having its
description updated, it causes the destructor to try to save
the changes to the database, and that sometimes throws a fatal
error if PHP garbage-collects the global $db variable before it
calls this constructor.

behatnotneeded: Covered by existing "edit_journal.feature"

Change-Id: I5056ecce91b823b245cb5bd29f0676a35a6afd45

[Mahara Bot (dev-mahara)]

Patch for "15.10_STABLE" branch: https://reviews.mahara.org/6163

[Mahara Bot (dev-mahara)]

Patch for "15.04_STABLE" branch: https://reviews.mahara.org/6164

[Mahara Bot (dev-mahara)]

Reviewed: https://reviews.mahara.org/6163
Committed: https://git.mahara.org/mahara/mahara/commit/875f1806be1e5a6931bb863b78698d67e1a96c24
Submitter: Robert Lyon (<email address hidden>)
Branch: 15.10_STABLE

commit 875f1806be1e5a6931bb863b78698d67e1a96c24
Author: Aaron Wells <email address hidden>
Date: Fri Nov 6 18:55:40 2015 +1300

Explicitly commit artefact to avoid buggy destructor (Bug 1513716)

Since this blog post object wasn't committed after having its
description updated, it causes the destructor to try to save
the changes to the database, and that sometimes throws a fatal
error if PHP garbage-collects the global $db variable before it
calls this constructor.

behatnotneeded: Covered by existing "edit_journal.feature"

Change-Id: I5056ecce91b823b245cb5bd29f0676a35a6afd45
(cherry picked from commit 294fa9a4edc5580cdc7a1c3c0c021e2f4b562884)

[Mahara Bot (dev-mahara)]

Reviewed: https://reviews.mahara.org/6164
Committed: https://git.mahara.org/mahara/mahara/commit/cfad522e53c796e6817f57778910edfa7daf32be
Submitter: Robert Lyon (<email address hidden>)
Branch: 15.04_STABLE

commit cfad522e53c796e6817f57778910edfa7daf32be
Author: Aaron Wells <email address hidden>
Date: Fri Nov 6 18:55:40 2015 +1300

Explicitly commit artefact to avoid buggy destructor (Bug 1513716)

Since this blog post object wasn't committed after having its
description updated, it causes the destructor to try to save
the changes to the database, and that sometimes throws a fatal
error if PHP garbage-collects the global $db variable before it
calls this constructor.

behatnotneeded: Covered by existing "edit_journal.feature"

Change-Id: I5056ecce91b823b245cb5bd29f0676a35a6afd45
(cherry picked from commit 294fa9a4edc5580cdc7a1c3c0c021e2f4b562884)