Instances share objects after copy or created from unpacking a dict

This is related to #154 and I’m using pydantic v0.12.1

Here is a simple example to show what I mean.

>>> class Model(pydantic.BaseModel):
...     my_dict: dict
...     
>>> model1 = Model(**{'my_dict': {'my_list': [1,2,3]}})
>>> model1
<Model my_dict={'my_list': [1, 2, 3]}>
>>> model2 = model1.copy()
>>> model2
<Model my_dict={'my_list': [1, 2, 3]}>
>>> model2.my_dict['my_list'] = []
>>> model2
<Model my_dict={'my_list': []}>
>>> model1
<Model my_dict={'my_list': []}>

Another example when created by unpacking a dictionary.

>>> my_dict = {'my_dict': {'my_list': [1,2,3]}}
>>> model1 = Model(**my_dict)
>>> model1
<Model my_dict={'my_list': [1, 2, 3]}>
>>> model2 = Model(**my_dict)
>>> model2
<Model my_dict={'my_list': [1, 2, 3]}>
>>> model2.my_dict['my_list'] = []
>>> model1
<Model my_dict={'my_list': []}>
>>> model2
<Model my_dict={'my_list': []}>

BaseModel.dict() seems to create copies correctly and can be used instead of .copy() to create a new object as seen with model3 in this example.

>>> model1 = Model(**{'my_dict': {'my_list': [1,2,3]}})
>>> model1
<Model my_dict={'my_list': [1, 2, 3]}>
>>> model2 = model1.copy()
>>> model2
<Model my_dict={'my_list': [1, 2, 3]}>
>>> model3 = Model(**model1.dict())
>>> model3
<Model my_dict={'my_list': [1, 2, 3]}>
>>> model2.my_dict['my_list'] = []
>>> model1
<Model my_dict={'my_list': []}>
>>> model2
<Model my_dict={'my_list': []}>
>>> model3
<Model my_dict={'my_list': [1, 2, 3]}>

I think this is quite serious since you can’t know if you are working with a true copy of a model or not.

I see two things that need to be fixed.

.copy() should create a deepcopy that doesn’t share any objects with the model it was copied from. User created classes have to support deepcopy operations to work correctly.

BaseModel(**dict) need to make sure that all items in the dict are deepcopied from the unpacked dictionary.

[samuelcolvin]

BTW, you can reference other issues with #<issue number> you don’t have to create a markdown link to the issue, this also has the advantage of showing the reference on the referenced issue.

[gangefors]

Took a little longer than expected before I had time to do this, but now it’s done.