Why isn't importing a private module from a third-party library considered an error?

[Delgan]

Hi.

I've read the docs about Library interface but I can't understand why isn't pyright reporting an error when I import private modules.

Consider first installing a third-party library like pydantic:

pip install pydantic==2.9.1

Then asking pyright to analyze the following file in "strict" mode:

# pyright: strict
import pydantic._migration

print(pydantic._migration.MOVED_IN_V2)

Because I'm importing and using _migration which is supposed to be a private module, I would expect an error such as reportPrivateUsage or reportPrivateImportUsage. However, the output is (for version 1.1.380):

0 errors, 0 warnings, 0 informations 

Is that intentional design? I understand that for unit tests within the library, it's preferable for library authors to be able to import a private module (and test some internal functions). But shouldn't this be forbidden for a library user?

[Eric Traut (erictraut)]

Pyright doesn't check for this currently, but I agree it would be a good feature enhancement. Converting the discussion into an issue to track this.

[Oliver Sheridan-Methven (oliversheridanmethven)]

There are some tools like flake8-self which try and do this, but none I can spot with the community momentum comparable to an established and popular type checker like this.