Mypy will not automatically check files with multiple dots in their names

[jacksonokuhn]

Bug Report

Files with names of the form x.y.py don't get checked by mypy.

To Reproduce

mkdir mypy-test
touch mypy-test/a.py
touch mypy-test/a.b.py
mypy mypy-test

Expected Behavior

You'd expect mypy to check two source files with the message Success: no issues found in 2 source files

Actual Behavior

Mypy only checks one source file: Success: no issues found in 1 source file

Your Environment

• Mypy version used: 0.790
• Mypy command-line flags: N/A
• Mypy configuration options from mypy.ini (and other config files): N/A
• Python version used: 3.7.4
• Operating system and version: Mac 10.15.7

[gvanrossum]

Those are not legal Python file names anyway.

[hauntsaninja]

As it happens, this is no longer the behaviour on master.
This is a side effect of #9742 making mypy dir/ behave more like mypy file.py. mypy already allowed mypy a.b.py, so it works with the recursive invocation now.

Note that all versions associate the file with the incorrect module name "a.b". I tried to improve this, but it caused a couple issues and I backtracked to keep the PR surface smaller. See point 2 of #9742 (comment)