#23473: Django prompts to create new migrations when none are needed when a
class
is used in a field declaration
----------------------------+---------------------------------------
Reporter: dlo | Owner: Markush2010
Type: Bug | Status: assigned
Component: Migrations | Version: 1.7
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
----------------------------+---------------------------------------
Comment (by Markush2010):
Replying to [comment:6 dlo]:
> Is there any way we could also make the `./manage.py makemigrations`
command fail unless `__eq__` is implemented? Otherwise, users might not
know where to look to fix the problem.
This is rather complicated as `object` itself has a `__eq__` method. and
would require some crazy comparisons. For what I've tested, this seems to
work.
Two solutions that somehow work, but that I'm not really a friend of. The
if clause is really error-prone.
1. Fails even on `manage.py shell`:
{{{#!python
diff --git a/django/utils/deconstruct.py b/django/utils/deconstruct.py
index a51a169..b0443ee 100644
--- a/django/utils/deconstruct.py
+++ b/django/utils/deconstruct.py
@@ -49,6 +49,13 @@ def deconstructible(*args, **kwargs):
klass.__new__ = staticmethod(__new__)
klass.deconstruct = deconstruct
+ if not hasattr(klass, '__eq__') or klass.__eq__ == object.__eq__:
+ raise ValueError(
+ "Cannot deconstruct class %s since no __eq__ method
exists or "
+ "__eq__ is inherited from 'object'. This method is
required "
+ "to prevent infinit migration creation"
+ % klass.__name__)
+
return klass
if not args:
}}}
2. Fails only when `__eq__` is called:
{{{#!python
diff --git a/django/utils/deconstruct.py b/django/utils/deconstruct.py
index a51a169..7c3abac 100644
--- a/django/utils/deconstruct.py
+++ b/django/utils/deconstruct.py
@@ -49,6 +49,16 @@ def deconstructible(*args, **kwargs):
klass.__new__ = staticmethod(__new__)
klass.deconstruct = deconstruct
+ if not hasattr(klass, '__eq__') or klass.__eq__ == object.__eq__:
+ def __eq__(obj, other):
+ raise ValueError(
+ "Cannot deconstruct class %s since no __eq__ method "
+ "exists or __eq__ is inherited from 'object'. This
method "
+ "is required to prevent infinit migration creation"
+ % obj.__class__.__name__)
+
+ klass.__eq__ = __eq__
+
return klass
if not args:
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/23473#comment:7>
Django <https://code.djangoproject.com/>
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