#33449: Migration autodetector fails for models with field named _order, but not
using Meta.order_with_respect_to
--------------------------------+--------------------------------------
Reporter: Fabian Büchler | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: 4.0
Severity: Normal | Resolution:
Keywords: | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
--------------------------------+--------------------------------------
Description changed by Fabian Büchler:
Old description:
> The commit
> [aa4acc1|https://github.com/django/django/commit/aa4acc164d1247c0de515c959f7b09648b57dc42]
> introduced a new function `ModelState.get_field` in
> `django.db.migrations.state`.
>
> This converts the field name `_order` to the one defined in
> `options['order_with_respect_to']` automatically, which fails if the
> model has a field `_order` but isn't using `Meta.order_with_respect_to`.
>
> That is the case for models generated by django-simple-history
> (https://github.com/jazzband/django-simple-history) for models that are
> originally using `Meta.order_with_respect_to`: the resulting historical
> records model has only `_order` but is not using the Meta option.
>
> This shows when running `mange.py migrate` or `manage.py makemigrations`:
>
>
> {{{#!python
> $ ./manage.py makemigrations --dry-run
> Waiting for port 'mysql:3306' timeout 1s (attempt 1/60)
> Port 'mysql:3306' is open
> Traceback (most recent call last):
> File "./manage.py", line 42, in <module>
> main()
> File "./manage.py", line 36, in main
> execute_from_command_line(sys.argv)
> File "/usr/local/lib/python3.8/site-
> packages/django/core/management/__init__.py", line 425, in
> execute_from_command_line
> utility.execute()
> File "/usr/local/lib/python3.8/site-
> packages/django/core/management/__init__.py", line 419, 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 373, in run_from_argv
> self.execute(*args, **cmd_options)
> File "/usr/local/lib/python3.8/site-
> packages/django/core/management/base.py", line 417, in execute
> output = self.handle(*args, **options)
> File "/usr/local/lib/python3.8/site-
> packages/django/core/management/base.py", line 90, in wrapped
> res = handle_func(*args, **kwargs)
> File "/usr/local/lib/python3.8/site-
> packages/django/core/management/commands/makemigrations.py", line 172, in
> handle
> changes = autodetector.changes(
> File "/usr/local/lib/python3.8/site-
> packages/django/db/migrations/autodetector.py", line 43, in changes
> changes = self._detect_changes(convert_apps, graph)
> File "/usr/local/lib/python3.8/site-
> packages/django/db/migrations/autodetector.py", line 189, in
> _detect_changes
> self.generate_altered_fields()
> File "/usr/local/lib/python3.8/site-
> packages/django/db/migrations/autodetector.py", line 928, in
> generate_altered_fields
> old_field = self.from_state.models[app_label,
> old_model_name].get_field(old_field_name)
> File "/usr/local/lib/python3.8/site-
> packages/django/db/migrations/state.py", line 689, in get_field
> self.options['order_with_respect_to']
> KeyError: 'order_with_respect_to'
> }}}
>
> I believe this could be solved using a bit more defensive code, like:
>
> {{{#!python
> def get_field(self, field_name):
> if field_name == '_order' and 'order_with_respect_to' in
> self.options:
> field_name = self.options['order_with_respect_to']
> return self.fields[field_name]
> }}}
New description:
The commit
https://github.com/django/django/commit/aa4acc164d1247c0de515c959f7b09648b57dc42
introduced a new function `ModelState.get_field` in
`django.db.migrations.state`.
This converts the field name `_order` to the one defined in
`options['order_with_respect_to']` automatically, which fails if the model
has a field `_order` but isn't using `Meta.order_with_respect_to`.
That is the case for models generated by django-simple-history
(https://github.com/jazzband/django-simple-history) for models that are
originally using `Meta.order_with_respect_to`: the resulting historical
records model has only `_order` but is not using the Meta option.
This shows when running `mange.py migrate` or `manage.py makemigrations`:
{{{#!python
$ ./manage.py makemigrations --dry-run
Waiting for port 'mysql:3306' timeout 1s (attempt 1/60)
Port 'mysql:3306' is open
Traceback (most recent call last):
File "./manage.py", line 42, in <module>
main()
File "./manage.py", line 36, in main
execute_from_command_line(sys.argv)
File "/usr/local/lib/python3.8/site-
packages/django/core/management/__init__.py", line 425, in
execute_from_command_line
utility.execute()
File "/usr/local/lib/python3.8/site-
packages/django/core/management/__init__.py", line 419, 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 373, in run_from_argv
self.execute(*args, **cmd_options)
File "/usr/local/lib/python3.8/site-
packages/django/core/management/base.py", line 417, in execute
output = self.handle(*args, **options)
File "/usr/local/lib/python3.8/site-
packages/django/core/management/base.py", line 90, in wrapped
res = handle_func(*args, **kwargs)
File "/usr/local/lib/python3.8/site-
packages/django/core/management/commands/makemigrations.py", line 172, in
handle
changes = autodetector.changes(
File "/usr/local/lib/python3.8/site-
packages/django/db/migrations/autodetector.py", line 43, in changes
changes = self._detect_changes(convert_apps, graph)
File "/usr/local/lib/python3.8/site-
packages/django/db/migrations/autodetector.py", line 189, in
_detect_changes
self.generate_altered_fields()
File "/usr/local/lib/python3.8/site-
packages/django/db/migrations/autodetector.py", line 928, in
generate_altered_fields
old_field = self.from_state.models[app_label,
old_model_name].get_field(old_field_name)
File "/usr/local/lib/python3.8/site-
packages/django/db/migrations/state.py", line 689, in get_field
self.options['order_with_respect_to']
KeyError: 'order_with_respect_to'
}}}
I believe this could be solved using a bit more defensive code, like:
{{{#!python
def get_field(self, field_name):
if field_name == '_order' and 'order_with_respect_to' in
self.options:
field_name = self.options['order_with_respect_to']
return self.fields[field_name]
}}}
--
--
Ticket URL: <https://code.djangoproject.com/ticket/33449#comment:1>
Django <https://code.djangoproject.com/>
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