Missing Member for Pydantic Model

[alvinmaottd]

Bug description

hey team, I'm running into:
E1101: Instance of 'Response' has no 'versionInfo' member (no-member)
Provided the following code:

☁  test_py  cat main.py 
from response import Response
from run import f

r = f()
r.versionInfo = r.versionInfo | {"hi":"bye"}
print(r)%                                                                                                                                                                                     ☁  test_py  cat response.py 
from pydantic import BaseModel


class Response(BaseModel):
    versionInfo: dict[str, str]
    fm: dict[int, float]
☁  test_py  cat run.py 
from response import Response

def f() -> Response:
  return Response(verionInfo={}, fm={})%

Running pylint on main.py I get the following:
main.py:5:16: E1101: Instance of 'Response' has no 'versionInfo' member (no-member)

However, versionInfo is defined in the Response class.

I've got a theory for what's wrong and a work around. Specifically, I think it has something to do with how the BaseModel in pydantic isn't defining the fields using self / something more python native. When I replace the BaseModel with a normal class and define the fields with self linting passes.

Curious what the team thought should be done here. It's not strictly a bug given it's related to a separate dependency in pydantic.

Configuration

pylint 2.17.0
astroid 2.15.0
Python 3.9.6 (default, May  7 2023, 23:32:44) 
[Clang 14.0.3 (clang-1403.0.22.14.1)]

Command used

☁  test_py  pylint main.py

Pylint output

************* Module main
main.py:6:0: C0304: Final newline missing (missing-final-newline)
main.py:1:0: C0114: Missing module docstring (missing-module-docstring)
main.py:5:16: E1101: Instance of 'Response' has no 'versionInfo' member (no-member)
main.py:1:0: W0611: Unused Response imported from response (unused-import)

------------------------------------------------------------------
Your code has been rated at 0.00/10 (previous run: 0.00/10, +0.00)

Expected behavior

************* Module main
main.py:6:0: C0304: Final newline missing (missing-final-newline)
main.py:1:0: C0114: Missing module docstring (missing-module-docstring)
main.py:1:0: W0611: Unused Response imported from response (unused-import)

^ no more:
main.py:5:16: E1101: Instance of 'Response' has no 'versionInfo' member (no-member)
or the option to do away with it.

Pylint version

pylint 2.17.0
astroid 2.15.0
Python 3.9.6 (default, May  7 2023, 23:32:44) 
[Clang 14.0.3 (clang-1403.0.22.14.1)]

OS / Environment

ProductName: macOS
ProductVersion: 13.4
BuildVersion: 22F66

Additional dependencies

No response

[mbyrnepr2]

Thank you @alvinmaottd. This is the same situation as the comment in issue 4562. While the fix in 4562 addressed the false negatives, it didn't address the false positive.

I've been thinking about what to do here and I wonder what others think about this: Re-introduce the false-negatives from 4562 while also removing the false positive. The rationale for doing this would be:

• It's part of Pylint goals to prefer false negatives over false positives
• It aligns with a potential design-change idea that has arisen recently (8756 comment and 6281 comment) around using .pyi files to check for a member if that member cannot be found in a .py module.

Note for simplicity of reproducing, I've re-written your code example:

from pydantic import BaseModel


class Response(BaseModel):
    versionInfo: dict[str, str]
    fm: dict[int, float]

rr = Response(versionInfo={}, fm={})
rr.versionInfo = rr.versionInfo | {"hi":"bye"}  # Currently a false-positive but we could change this behaviour to ignore no-member if we find `versionInfo: <some annotation>` on the class

@Pierre-Sassoulas do you think this is feasible?