When given directory mypy only analyzes files with PY_EXTENSIONS

I have a Python script with __main__ in a file that has no extension

When the file is supplied to mypy directly it can evaluate it due to the code found here.

❯ mypy --scripts-are-modules --strict tools/docker2sqlelf | head
tools/docker2sqlelf:10: error: Skipping analyzing "docker": module is installed, but missing library stubs or py.typed marker  [import-untyped]
tools/docker2sqlelf:10: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
tools/docker2sqlelf:21: error: Function is missing a return type annotation  [no-untyped-def]
tools/docker2sqlelf:21: note: Use "-> None" if function does not return a value
tools/docker2sqlelf:75: error: Incompatible return value type (got "str", expected "int")  [return-value]
Found 3 errors in 1 file (checked 1 source file)

However if I give the directory the file is in, it is skipped due to the logic in find_sources_in_dir.

❯ mypy --scripts-are-modules --strict tools | head
Success: no issues found in 1 source file

Here is the contents of the directory tools:

❯ tree tools
tools
├── debian-unstable-tags.txt
├── docker2sqlelf
├── __init__.py
├── README.md
└── unstable2sqlelf

1 directory, 5 files

• Mypy version used:

❯ mypy --version
mypy 1.8.0 (compiled: yes)

• Python version used: 3.10 and 3.11

Inspect mypy/find_sources.py, starting with the direct-file handling near the linked code and find_sources_in_dir. Reproduce the difference with mypy --scripts-are-modules --strict tools/docker2sqlelf and with tools, then verify that directory analysis includes extensionless Python scripts while preserving the reported diagnostics.