Fixed custom __init__ check in transmogrify

[bdabrowski]

Fixes #615

[Copilot]

Pull request overview

This PR fixes a bug in the polymorphic object retrieval mechanism where custom __init__ methods were not being called when transmogrifying objects between related classes. The issue occurred because the code was checking for __init__ in the instance's __dict__ (which would never contain class methods) instead of the class's __dict__. The fix changes the check from obj.__dict__ to obj.__class__.__dict__, ensuring that custom initialization logic is properly executed when converting polymorphic instances.

Key Changes:

• Fixed the __init__ existence check in the transmogrify() function to correctly identify custom initialization methods
• Added test models (BlueHeadDuck, HomeDuck, PurpleHeadDuck) to demonstrate the bug scenario with proxy models and multiple inheritance
• Added a regression test to ensure custom __init__ methods are called during polymorphic object retrieval

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
src/polymorphic/query.py	Fixed the bug by changing the __init__ check from obj.__dict__ to obj.__class__.__dict__ in the transmogrify() function
src/polymorphic/tests/models.py	Added test models (BlueHeadDuck, HomeDuck, PurpleHeadDuck) to support testing the fix with proxy models and custom __init__ methods
src/polymorphic/tests/test_orm.py	Added test_transmogrify_with_init test case and updated imports to include new test models
src/polymorphic/tests/migrations/0001_initial.py	Regenerated migration file to include the new test models (Duck, BlueHeadDuck, PurpleHeadDuck)

Comments suppressed due to low confidence (1)

src/polymorphic/tests/test_orm.py:1416

• Normal methods should have 'self', rather than 'db', as their first parameter.

    def test_transmogrify_with_init(db):

---

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 75.40%. Comparing base (347ef6d) to head (59cfde0).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #614      +/-   ##
==========================================
+ Coverage   74.96%   75.40%   +0.44%     
==========================================
  Files          21       21              
  Lines        1342     1342              
  Branches      211      211              
==========================================
+ Hits         1006     1012       +6     
+ Misses        261      257       -4     
+ Partials       75       73       -2     

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[bckohan]

The custom __init__ transmogrify code was dead because it erroneously looked at the object dict to locate an __init__ implementation instead of the class __dict__.

I think there is still an edge case here where values set differently by the base class and subclass's __init__ may be overridden after the subclass instantiation - but its hard to solve for that and this code is certainly more correct.

Thank you!