Add type checking with mypy

[araffin]

Description

Counterpart of DLR-RM/stable-baselines3#1143

Motivation and Context

• I have raised an issue to propose this change (required for new features and bug fixes)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation (update in the documentation)

Checklist:

• I've read the CONTRIBUTION guide (required)
• I have updated the changelog accordingly (required).
• My change requires a change to the documentation.
• I have updated the tests accordingly (required for a bug fix or a new feature).
• I have updated the documentation accordingly.
• I have reformatted the code using make format (required)
• I have checked the codestyle using make check-codestyle and make lint (required)
• I have ensured make pytest and make type both pass. (required)

Note: we are using a maximum length of 127 characters per line

[qgallouedec]

Should we also add --install-types --non-interactive in sb3 and sb3-contrib?

[araffin]

I would only if it was needed.

[qgallouedec]

de67905: python/mypy#2427

[araffin]

It's weird, mypy check passes locally, I guess it has something to do with the way we package SB3 / SB3 contrib, maybe the stubs are missing? (locally I have them installed in editable mode)

[qgallouedec]

Same here

[araffin]

I can reproduce some errorr locally: pip install . vs pip install -e . (for sb3-contrib) with python 3.8 and latest mypy version.

and surprisingly, I've got more errors on my laptop that on the PC I used to do the PR.

[qgallouedec]

I can reproduce some errorr locally: pip install . vs pip install -e . (for sb3-contrib) with python 3.8 and latest mypy version.

and surprisingly, I've got more errors on my laptop that on the PC I used to do the PR.

Have you checked that the sb3/sb3-contrib versions match?

[araffin]

Have you checked that the sb3/sb3-contrib versions match?

yes, I'm using master version of both

[qgallouedec]

Same here

Actually, no, I just forgot to stage setup.cfg in my last commit.