Support invoking mypy from setuptools

By default, this will typecheck all of the package modules.
We still need to figure out how to handle third-party modules.
Passing in `--mypy-args="--use-python-path"` will also include
any dependent modules, but nearly all of them fail to typecheck.

This will fix python#992

mypy/build.py

@@ -203,6 +203,10 @@ def default_data_dir(bin_dir: str) -> str:
     # TODO fix this logic
     if not bin_dir:
         # Default to directory containing this file's parent.
+        grandparent_dir = os.path.dirname(os.path.dirname(__file__))
+        # Running from within an egg, likely from setuptools.
+        if grandparent_dir.endswith('.egg'):
+            return os.path.join(grandparent_dir, 'lib', 'mypy')
         return os.path.dirname(os.path.dirname(__file__))
     base = os.path.basename(bin_dir)
     dir = os.path.dirname(bin_dir)

mypy/main.py

@@ -2,11 +2,14 @@
 
 import os
 import os.path
+import shlex
 import shutil
 import subprocess
 import sys
 import tempfile
 
+import setuptools as setuptools  # type: ignore
+
 import typing
 from typing import Dict, List, Tuple
 
@@ -31,6 +34,45 @@ def __init__(self) -> None:
         self.dirty_stubs = False
 
 
+class MyPyCommand(setuptools.Command):
+    """The :class:`MyPyCommand` class is used by setuptools to perform
+    type checks on registered modules.
+    """
+
+    description = "Validate PEP 0484 Types with mypy"
+    user_options = [
+        ('mypy-args=', None, 'Arguments to pass through to mypy')
+    ]  # type: List[tuple]
+
+    def initialize_options(self):
+        self.mypy_args = ''
+
+    def finalize_options(self):
+        pass
+
+    def run(self):
+        try:
+            mypy_options = []
+            for package in set(self.distribution.packages):
+                mypy_options.append('--package')
+                mypy_options.append(package)
+            mypy_options.extend(shlex.split(self.mypy_args))
+            sources, options = process_options(mypy_options)
+            # If the user has requested to use the python_path during analysis,
+            # fetch all required eggs (This will also add them to sys.path).
+            # This will ensure mypy behaves as if the package were installed
+            # globally without having to globally install it to modify
+            # PYTHONPATH
+            if options.python_path and self.distribution.install_requires:
+                self.distribution.fetch_build_eggs(
+                    self.distribution.install_requires)
+            type_check_only(sources, None, options)
+        except CompileError as e:
+            for m in e.messages:
+                sys.stderr.write(m + '\n')
+            sys.exit(1)
+
+
 def main(script_path: str) -> None:
     """Main entry point to the type checker.
 

setup.py

@@ -5,7 +5,7 @@
 import os.path
 import sys
 
-from distutils.core import setup
+from setuptools import setup
 from mypy.version import __version__
 from mypy import git
 
@@ -69,6 +69,13 @@ def find_data_files(base, globs):
     'Topic :: Software Development',
 ]
 
+entry_points = {
+    'distutils.commands': [
+        'mypy = mypy.main:MyPyCommand'
+    ]
+}
+
+
 setup(name='mypy-lang',
       version=version,
       description=description,
@@ -84,4 +91,5 @@ def find_data_files(base, globs):
       scripts=['scripts/mypy'],
       data_files=data_files,
       classifiers=classifiers,
+      entry_points=entry_points,
       )