support self argument

[samuelcolvin]

fix #629

Checklist

• Unit tests for the changes exist
• Tests pass on CI and coverage remains at 100%
• Documentation reflects the changes where applicable
• HISTORY.rst has been updated
  • if this is the first change since a release, please add a new section
  • include the issue number or this pull request number #<number>
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[skaaptjop]

@samuelcolvin so that would work if 'self' is at the root of the dict but if it's nested it doesn't.
e.g.

from pydantic import BaseModel

class Nested(BaseModel):
    self: str

class Model(BaseModel):
    nested: Nested

m = Model.parse_obj({"nested": {"self": "me"}})
#pydantic.error_wrappers.ValidationError: 1 validation error
#nested
# __init__() got multiple values for argument 'self' (type=type_error)

[skaaptjop]

That seems to do it.

[codecov]

Codecov Report

Merging #632 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff          @@
##           master   #632   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files          15     15           
  Lines        2651   2632   -19     
  Branches      524    516    -8     
=====================================
- Hits         2651   2632   -19

[dgasmith]

Note that this breaks nested models that overload a BaseModel's __init__.

[samuelcolvin]

Humm, hadn't thought of that.

Anything we can do? Or just add a note to the release notes.

[dgasmith]

If I understand the issue correctly, the first argument in the __init__ should be renamed:

class MyClass:

    def __init__(my_custom_self_name, self=5):
        my_custom_self_name = self

a = MyClass(self=3)

print(a.self)

You could even to rename it to something like pydantic_base_model_init to ensure no collisions would occur.

I think supporting canonical init overloading is relatively important. The @validators work really well for most cases, but complex cases where I need to share state before/after the BaseModel init and it starts to become a bit more clunky.