#26739: Backward operation for RemoveField does not allow a default value in
case
the field is not null.
----------------------------+--------------------
Reporter: Gagaro | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: master
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
----------------------------+--------------------
If a field does not allow NULL and has no default, and this field is
removed using RemoveField, the backward operation will break if the
database is populated because the field will be created with no value.
Replication:
models.py
{{{
class TestModel(Model):
field = CharField(max_length=255)
}}}
{{{
$ python manage.py makemigrations
$ python manage.py migrate
$ python manage.py shell
>>> TestModel.objects.create(field='test')
}}}
models.py
{{{
class TestModel(Model):
pass
}}}
{{{
$ python manage.py makemigrations
$ python manage migrate
$ python manage migrate app 0001
}}}
POC Patch made by apollo13 in IRC:
{{{
diff --git a/django/db/migrations/operations/fields.py
b/django/db/migrations/operations/fields.py
index 041f8a6..5604e36 100644
--- a/django/db/migrations/operations/fields.py
+++ b/django/db/migrations/operations/fields.py
@@ -122,6 +122,10 @@ class RemoveField(FieldOperation):
Removes a field from a model.
"""
+ def __init__(self, *args, **kwargs):
+ self.default = kwargs.pop('default', None)
+ super(RemoveField, self).__init__(*args, **kwargs)
+
def deconstruct(self):
kwargs = {
'model_name': self.model_name,
@@ -150,7 +154,12 @@ class RemoveField(FieldOperation):
to_model = to_state.apps.get_model(app_label, self.model_name)
if self.allow_migrate_model(schema_editor.connection.alias,
to_model):
from_model = from_state.apps.get_model(app_label,
self.model_name)
- schema_editor.add_field(from_model,
to_model._meta.get_field(self.name))
+ to_field = to_model._meta.get_field(self.name)
+ old_default = to_field.default
+ if self.default is not None:
+ to_field.default = self.default
+ schema_editor.add_field(from_model, to_field)
+ to_field.default = old_default
def describe(self):
return "Remove field %s from %s" % (self.name, self.model_name)
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/26739>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.
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