Detect missing pydantic dependency (e.g. pydantic-settings or extra types)

[kkirsche]

Hey team,

I wasn't sure if you would be comfortable with this, but what's your opinion on telling the user when they are missing a pydantic dependency, such as pydantic-settings is using BaseSettings in Pydantic V1?

This could spit out a warning (whether that's stdout, stderr, log.txt, or somewhere else) or a # TODO comment if the pydantic-settings package isn't installed.

This will help users more quickly identify when their application requires packages that are not currently installed.

To detect if a package is installed without importing it (for safety reasons), importlib.util can be used:

from importlib.util import find_spec

print(find_spec("pydantic-settings"))
# ''

print(find_spec("pydantic"))
# 'ModuleSpec(name='pydantic', loader=<_frozen_importlib_external.SourceFileLoader object at 0x104e18240>, origin='/Users/kkirsche/.asdf/installs/python/3.11.4/lib/python3.11/site-packages/pydantic/__init__.py', submodule_search_locations=['/Users/kkirsche/.asdf/installs/python/3.11.4/lib/python3.11/site-packages/pydantic'])'

Documentation on find_spec:
https://docs.python.org/3/library/importlib.html#importlib.util.find_spec

[Kludex]

Hmmm... I think it makes sense to log a message telling the user to install it. 👍

[Kludex]

PR welcome to add a TODO above the import pydantic_settings.

[Kludex]

Actually, a message on stdout would be better.