Add infrastructure support for static type-checking using mypy

.gitignore

@@ -5,6 +5,7 @@ pip.egg-info/
 MANIFEST
 .tox
 .cache
+.mypy_cache
 *.egg
 *.eggs
 *.py[cod]

.travis.yml

@@ -7,6 +7,7 @@ matrix:
     - env: TOXENV=docs
     - env: TOXENV=lint-py2
     - env: TOXENV=lint-py3
+    - env: TOXENV=mypy
     - env: TOXENV=packaging
     # PyPy jobs start first -- they are the slowest
     - env: TOXENV=pypy

MANIFEST.in

@@ -18,6 +18,9 @@ exclude appveyor.yml
 recursive-include src/pip/_vendor *.pem
 recursive-include docs Makefile *.rst *.py *.bat
 
+exclude src/pip/_vendor/six
+recursive-exclude src/pip/_vendor *.pyi
+
 prune .github
 prune .travis
 prune docs/_build

news/4545.feature

@@ -0,0 +1 @@
+Integrate with mypy for utilizing static typing.

setup.cfg

@@ -11,9 +11,19 @@ known_first_party =
 default_section = THIRDPARTY
 
 [flake8]
+# Ignoring unused imports since mypy would warn of that.
+ignore = F401
 exclude = .tox,.idea,*.egg,build,_vendor,data
 select = E,W,F
 
+[mypy]
+follow_imports = silent
+ignore_missing_imports = True
+
+[mypy-pip/_vendor/*]
+follow_imports = skip
+ignore_errors = True
+
 [tool:pytest]
 addopts = --ignore src/pip/_vendor --ignore tests/tests_cache
 

src/pip/_internal/__init__.py

@@ -55,15 +55,6 @@
     InsecureRequestWarning,
 )
 
-
-# assignment for flake8 to be happy
-
-# This fixes a peculiarity when importing via __import__ - as we are
-# initialising the pip module, "from pip import cmdoptions" is recursive
-# and appears not to work properly in that situation.
-# import pip._internal.cmdoptions
-# cmdoptions = pip._internal.cmdoptions
-
 logger = logging.getLogger(__name__)
 
 # Hide the InsecureRequestWarning from urllib3
@@ -241,7 +232,7 @@ def main(args=None):
         sys.exit(1)
 
     # Needed for locale.getpreferredencoding(False) to work
-    # in pip.utils.encoding.auto_decode
+    # in pip._internal.utils.encoding.auto_decode
     try:
         locale.setlocale(locale.LC_ALL, '')
     except locale.Error as e:

src/pip/_internal/basecommand.py

@@ -20,7 +20,8 @@
 )
 from pip._internal.index import PackageFinder
 from pip._internal.locations import running_under_virtualenv
-from pip._internal.req import InstallRequirement, parse_requirements
+from pip._internal.req.req_file import parse_requirements
+from pip._internal.req.req_install import InstallRequirement
 from pip._internal.status_codes import (
     ERROR, PREVIOUS_BUILD_DIR_ERROR, SUCCESS, UNKNOWN_ERROR,
     VIRTUALENV_NOT_FOUND
@@ -29,18 +30,21 @@
 from pip._internal.utils.logging import IndentingFormatter
 from pip._internal.utils.misc import get_prog, normalize_path
 from pip._internal.utils.outdated import pip_version_check
+from pip._internal.utils.typing import MYPY_CHECK_RUNNING
 
-__all__ = ['Command']
+if MYPY_CHECK_RUNNING:
+    from typing import Optional
 
+__all__ = ['Command']
 
 logger = logging.getLogger(__name__)
 
 
 class Command(object):
-    name = None
-    usage = None
-    hidden = False
-    ignore_require_venv = False
+    name = None  # type: Optional[str]
+    usage = None  # type: Optional[str]
+    hidden = False  # type: bool
+    ignore_require_venv = False  # type: bool
     log_streams = ("ext://sys.stdout", "ext://sys.stderr")
 
     def __init__(self, isolated=False):