#25616: Add note regarding missing dependencies on LookupError for migrations
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Reporter: mcfletch | Owner: nobody
Type: Cleanup/optimization | Status: new
Component: Migrations | Version: master
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 1 | UI/UX: 0
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If you have a product package that includes migrations which depend on a
plugin package, and you forget to include a dependency on the migration,
you wind up with a confusing error message (raised from
Apps.get_app_config):
{{{
LookupError("No installed app with label '%s'"%(label,))
}}}
where label is the name of the "missing" app. Which then leads the user to
trying to figure out why the app, which is in settings.py is not showing
up.
It would be helpful, in `django.db.migrations.state` if we were to
annotate the LookupError with the common issue the user is likely seeing,
something like (on StateApps):
{{{
def get_app_config(self, app_label):
try:
return super(StateApps, self).get_app_config(app_label)
except LookupError as err:
err.args += ('Possibly missing dependency on a migration?', )
raise
}}}
I'm not attached to the particular implementation or wording, just
suggesting that the error message should be cleaner in the migrations-
can't-find-app case, which is different than the general "can't find an
app of that name" case.
--
Ticket URL: <https://code.djangoproject.com/ticket/25616>
Django <https://code.djangoproject.com/>
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