Fix a regression in dotenv optional nested field

[hramezani]

No description provided.

[hsuyuming]

Let me pull this branch and test it within my local. Will provide the feedback when i get the result. Thank you!

[hsuyuming]

Hi @hramezani :

I cloned your "issue-420" branch and installed it using pip install -e .. After testing, this fix resolved the issue. I truly appreciate your quick response and excellent work!

(.venv) user@jupyter:~/abehsu/pydantic-settings$ pip install -e .
Obtaining file:///home/user/abehsu/pydantic-settings
  Installing build dependencies ... done
  Checking if build backend supports build_editable ... done
  Getting requirements to build editable ... done
  Installing backend dependencies ... done
  Preparing editable metadata (pyproject.toml) ... done
Requirement already satisfied: pydantic>=2.7.0 in ./.venv/lib/python3.10/site-packages (from pydantic-settings==2.5.2) (2.9.1)
Requirement already satisfied: python-dotenv>=0.21.0 in ./.venv/lib/python3.10/site-packages (from pydantic-settings==2.5.2) (1.0.1)
Requirement already satisfied: annotated-types>=0.6.0 in ./.venv/lib/python3.10/site-packages (from pydantic>=2.7.0->pydantic-settings==2.5.2) (0.7.0)
Requirement already satisfied: pydantic-core==2.23.3 in ./.venv/lib/python3.10/site-packages (from pydantic>=2.7.0->pydantic-settings==2.5.2) (2.23.3)
Requirement already satisfied: typing-extensions>=4.6.1 in ./.venv/lib/python3.10/site-packages (from pydantic>=2.7.0->pydantic-settings==2.5.2) (4.12.2)
Building wheels for collected packages: pydantic-settings
  Building editable for pydantic-settings (pyproject.toml) ... done
  Created wheel for pydantic-settings: filename=pydantic_settings-2.5.2-py3-none-any.whl size=3008 sha256=97aad59cab642606f0923ccbc2fa3338f682b31ecfce35798d4ff61220b9ca4f
  Stored in directory: /tmp/pip-ephem-wheel-cache-2yrcwtb0/wheels/26/74/6f/a4558daf38621005fce811c2e94a8d499c396a7ff00be6fccf
Successfully built pydantic-settings
Installing collected packages: pydantic-settings
  Attempting uninstall: pydantic-settings
    Found existing installation: pydantic-settings 2.5.2
    Uninstalling pydantic-settings-2.5.2:
      Successfully uninstalled pydantic-settings-2.5.2
Successfully installed pydantic-settings-2.5.2
(.venv) user@jupyter~/abehsu/pydantic-settings$ python /home/user/abehsu/pydantic-settings/test.py
contents=InputModel(el_type='input', class_name='123', value=None)

[hramezani]

Thanks @hsuyuming for checking!

The fix will be available in the next release.