Showmigrations applied timestamp can cause runtime error

[Daniel Ebrahimian]

The functionality of showmigrations --verbosity 2 will show the applied timestamps for migrations.

In certain scenarios, a timestamp isn't available and will cause a run time error of

AttributeError: 'Migration' object has no attribute 'applied'.

An example of this is having social_django migrations in a project.

Proposed solution: Safely check for the applied timestamp to exist before logging it.

Current workaround: Don't use --verbosity 2

Logs

This shows the type for the applied_migration

<class 'django.db.migrations.recorder.MigrationRecorder.Migration.<locals>.Migration'>
 [X] 0045_auto_20201125_0810 (applied at 2021-01-13 23:39:40)
<class 'django.db.migrations.recorder.MigrationRecorder.Migration.<locals>.Migration'>
 [X] 0046_auto_20201218_0440 (applied at 2021-01-13 23:39:42)
sessions
<class 'django.db.migrations.recorder.MigrationRecorder.Migration.<locals>.Migration'>
 [X] 0001_initial (applied at 2021-01-13 23:40:46)
social_django
<class 'social_django.migrations.0001_initial.Migration'>
Traceback (most recent call last):
  File "real_manage.py", line 23, in <module>
    execute_from_command_line(sys.argv)
  File "/usr/local/lib/python3.8/site-packages/django/core/management/__init__.py", line 401, in execute_from_command_line
    utility.execute()
  File "/usr/local/lib/python3.8/site-packages/django/core/management/__init__.py", line 395, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/local/lib/python3.8/site-packages/django/core/management/base.py", line 328, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/usr/local/lib/python3.8/site-packages/django/core/management/base.py", line 369, in execute
    output = self.handle(*args, **options)
  File "/usr/local/lib/python3.8/site-packages/django/core/management/commands/showmigrations.py", line 52, in handle
    return self.show_list(connection, options['app_label'])
  File "/usr/local/lib/python3.8/site-packages/django/core/management/commands/showmigrations.py", line 97, in show_list
    output += ' (applied at %s)' % applied_migration.applied.strftime('%Y-%m-%d %H:%M:%S')
AttributeError: 'Migration' object has no attribute 'applied'

This is after the proposed pull request

 [X] 0045_auto_20201125_0810 (applied at 2021-01-13 23:39:40)
<class 'django.db.migrations.recorder.MigrationRecorder.Migration.<locals>.Migration'>
 [X] 0046_auto_20201218_0440 (applied at 2021-01-13 23:39:42)
sessions
<class 'django.db.migrations.recorder.MigrationRecorder.Migration.<locals>.Migration'>
 [X] 0001_initial (applied at 2021-01-13 23:40:46)
social_django
<class 'social_django.migrations.0001_initial.Migration'>
 [X] 0001_initial (2 squashed migrations)
<class 'social_django.migrations.0002_add_related_name.Migration'>
 [X] 0002_add_related_name (2 squashed migrations)

​https://github.com/django/django/pull/13890

[Simon Charette]

It looks like the issue is related to the usage of replaces which is relied upon the squashmigrations feature.

Tentatively accepting if you're able to write a test that triggers a crash when relying on a supported usage of replaces (e.g. a migration squash).

It looks like social-app-django ships with a complex graph of migrations to replace django-social-auth migrations

e.g. ​https://github.com/python-social-auth/social-app-django/blob/7a105df36ca579389b93911f748ee297ce141bb3/social_django/migrations/0001_initial.py#L29-L32

[Daniel Ebrahimian]

Thanks for the feedback. I have added unit tests for this change. Please review

[Daniel Ebrahimian]

When running the unit tests locally, the output contains terminal colour escape sequences. I have included them when writing the unit tests. However, when picked up by CI, the output differs.

​https://djangoci.com/job/pr-mariadb/database=mysql,label=mariadb,python=python3.9/9872/testReport/junit/migrations.test_commands/MigrateTests/test_showmigrations_list_squashed/

I have executed tests locally with

python runtests.py migrations.test_commands.MigrateTests.test_showmigrations_list_squashed

Testing against Django installed in '/Users/daniel/Documents/GenesisCare/projects/django/django'
Creating test database for alias 'default'...
Creating test database for alias 'other'...
System check identified no issues (0 silenced).
Running pre-migrate handlers for application migrations
Running post-migrate handlers for application migrations
.
----------------------------------------------------------------------
Ran 1 test in 0.017s

OK
Destroying test database for alias 'default'...
Destroying test database for alias 'other'...

Please advise whether these codes should be removed and how to then reproduce CI testing practices locally.

[Daniel Ebrahimian]

I have pushed changes, CI is now passing. @Simon Charette

[Simon Charette]

LGTM pending some cosmetic changes. The stdout pollution when running tests is handled by #32395.

[Mariusz Felisiak <felisiak.mariusz@…>]

In 3f8979e3:

Fixed #32350 -- Fixed showmigrations crash for applied squashed migrations.

Thanks Simon Charette for reviews.