--package flag does not work with installed packages

[apljungquist]

In short, I expect the below to not fail

mypy -p mypy
# Can't find package 'mypy'

The way I read the documentation and related issues such as 6394, the --package option should find named package among installed packages and check it recursively. For instance, I expect mypy to be be able to type check itself. As demonstrated this Is not the case.

The --module option on the other hand works fine:

mypy -m mypy
# no output

Explicitly setting the MYPYPATH resolves the issue:

MYPYPATH=venv/lib/python3.7/site-packages mypy -p mypy
# lots of output

However, this solution does not work inside tox where mypy will complain .tox/py37-mypypath-m/lib/python3.7/site-packages is in the MYPYPATH. Please remove it.

It would be nice to be able to check typing on the package under development as an installed package because this would ensure that the package appears as typing enabled to third parties.

I uploaded a small package that also reproduces the problem here

OS: MacOS 10.14.5
Python: 3.7.2 (via pyenv)
Mypy: 0.720+dev.17b68c6b7eaa76853422544e32b1d6c5c3acc55a

[ilevkivskyi]

Hm, I would say this should work (unless I am missing something).

cc @gvanrossum @ethanhs

[gvanrossum]

Unfortunately the -p option doesn't use the same code as the import-following code, and currently only the latter supports searching site-packages (etc.) for packages with a py.typed marker in them (which mypy has). It looks like the code for -m does use the import-following code (by calling BuildSource(None, m, None)).

Agreed we should fix this. If you can come up with a PR that would be awesome!

[bhrutledge]

I discovered this while working on pypa/twine#618, and thinking that it would be nice to run mypy against the installed package. See the comments for more details (including some proposed tox configurations).

Poking around a bit, it seems like this is the entry point to the import-following code for -p and -m:

mypy/mypy/main.py

Lines 900 to 917 in 22e504b

	# Set target.
	if special_opts.modules + special_opts.packages:
	options.build_type = BuildType.MODULE
	search_paths = SearchPaths((os.getcwd(),), tuple(mypy_path() + options.mypy_path), (), ())
	targets = []
	# TODO: use the same cache that the BuildManager will
	cache = FindModuleCache(search_paths, fscache, options, special_opts.packages)
	for p in special_opts.packages:
	if os.sep in p or os.altsep and os.altsep in p:
	fail("Package name '{}' cannot have a slash in it.".format(p),
	stderr)
	p_targets = cache.find_modules_recursive(p)
	if not p_targets:
	fail("Can't find package '{}'".format(p), stderr)
	targets.extend(p_targets)
	for m in special_opts.modules:
	targets.append(BuildSource(None, m, None))
	return targets, options

[apljungquist]

This appears to be working now. Big thanks to whoever fixed it.

[fitzymj]

It's not working for me! I'm on mypy-0.812.

[apljungquist]

@fitzymj Curious. In what sense does it not work for you?

I set up a somewhat controlled job to sanity check myself and my conclusion is still that it works. Notice how the older version fails because it does not find the package to type check whereas the new version fails because the type check fails.

[fitzymj]

Could be because I'm on Python 3.7, could be because I'm on Windows? This shows it pretty clearly:

c:\>python -V
Python 3.7.4

c:\>mypy -V
mypy 0.812

c:\>mkdir mypackage

c:\>mkdir mypackage\testpkg

c:\>echo from . import test  1>mypackage\testpkg\__init__.py

c:\>echo print("test.py imported")  1>mypackage\testpkg\test.py

c:\>echo from setuptools import setup; setup(packages=["testpkg"])  1>mypackage\setup.py

c:\>pip install -e mypackage
Obtaining file:///C:/mypackage
Installing collected packages: UNKNOWN
  Found existing installation: UNKNOWN 0.0.0
    Uninstalling UNKNOWN-0.0.0:
      Successfully uninstalled UNKNOWN-0.0.0
  Running setup.py develop for UNKNOWN
Successfully installed UNKNOWN

c:\>python -c "import testpkg"
test.py imported

c:\>mypy -p testpkg
Can't find package 'testpkg'

[apljungquist]

Is py.typed included among the files installed for your package?

Look in a path like venv/lib/python3.7/site-packages/testpkg, changing venv as appropriate for your installation.

This is the relevant part of the docs.

[fitzymj]

That did it, thanks! I went back to 0.782 and it did not fix it, so I feel a little better.

Ditto on the thanks to whomever fixed it in 0.812!

[apljungquist]

You are welcome.