fix: add mypy checking + 'py.typed' files

.coveragerc

@@ -3,9 +3,9 @@ branch = True
 
 [report]
 omit =
-    google/cloud/_testing.py
     google/cloud/__init__.py
-    google/cloud/environment_vars.py
+    google/cloud/_testing/__init__.py
+    google/cloud/environment_vars/__init__.py
 fail_under = 100
 show_missing = True
 exclude_lines =

google/__init__.py

@@ -21,4 +21,4 @@
 except ImportError:
     import pkgutil
 
-    __path__ = pkgutil.extend_path(__path__, __name__)
+    __path__ = pkgutil.extend_path(__path__, __name__)  # type: ignore

google/cloud/__init__.py

@@ -21,4 +21,4 @@
 except ImportError:
     import pkgutil
 
-    __path__ = pkgutil.extend_path(__path__, __name__)
+    __path__ = pkgutil.extend_path(__path__, __name__)  # type: ignore

google/cloud/_helpers.py → google/cloud/_helpers/__init__.py

@@ -25,6 +25,7 @@
 import os
 import re
 from threading import local as Local
+from typing import Union
 
 import google.auth
 import google.auth.transport.requests
@@ -62,6 +63,7 @@
 )
 # NOTE: Catching this ImportError is a workaround for GAE not supporting the
 #       "pwd" module which is imported lazily when "expanduser" is called.
+_USER_ROOT: Union[str, None]
 try:
     _USER_ROOT = os.path.expanduser("~")
 except ImportError:  # pragma: NO COVER

google/cloud/_helpers/py.typed

@@ -0,0 +1,2 @@
+# Marker file for PEP 561.
+# This package uses inline types.

google/cloud/_http/py.typed

@@ -0,0 +1,2 @@
+# Marker file for PEP 561.
+# This package uses inline types.

google/cloud/_testing/py.typed

@@ -0,0 +1,2 @@
+# Marker file for PEP 561.
+# This package uses inline types.

google/cloud/client.py → google/cloud/client/__init__.py

@@ -18,6 +18,8 @@
 import json
 import os
 from pickle import PicklingError
+from typing import Tuple
+from typing import Union
 
 import google.api_core.client_options
 import google.api_core.exceptions
@@ -142,7 +144,7 @@ class Client(_ClientFactoryMixin):
             to acquire default credentials.
     """
 
-    SCOPE = None
+    SCOPE: Union[Tuple[str], None] = None
     """The scopes required for authenticating with a service.
 
     Needs to be set by subclasses.

google/cloud/client/py.typed

@@ -0,0 +1,2 @@
+# Marker file for PEP 561.
+# This package uses inline types.

google/cloud/environment_vars/py.typed

@@ -0,0 +1,2 @@
+# Marker file for PEP 561.
+# This package uses inline types.

google/cloud/exceptions/py.typed

@@ -0,0 +1,2 @@
+# Marker file for PEP 561.
+# This package uses inline types.

google/cloud/obsolete/py.typed

@@ -0,0 +1,2 @@
+# Marker file for PEP 561.
+# This package uses inline types.

google/cloud/operation.py → google/cloud/operation/__init__.py

@@ -14,13 +14,15 @@
 
 """Wrap long-running operations returned from Google Cloud APIs."""
 
+from typing import Dict
+
 from google.longrunning import operations_pb2
 from google.protobuf import json_format
 
 
 _GOOGLE_APIS_PREFIX = "type.googleapis.com"
 
-_TYPE_URL_MAP = {}
+_TYPE_URL_MAP: Dict[str, type] = {}
 
 
 def _compute_type_url(klass, prefix=_GOOGLE_APIS_PREFIX):

google/cloud/operation/py.typed

@@ -0,0 +1,2 @@
+# Marker file for PEP 561.
+# This package uses inline types.

mypy.ini

@@ -0,0 +1,7 @@
+[mypy]
+python_version = 3.6
+namespace_packages = True
+ignore_missing_imports = True
+
+[mypy-google.protobuf]
+ignore_missing_imports = True

noxfile.py

@@ -38,6 +38,16 @@ def lint(session):
     session.run("flake8", "google", "tests")
 
 
+@nox.session(python=DEFAULT_PYTHON_VERSION)
+def mypy(session):
+    """Run type-checking."""
+    session.install(".", "mypy")
+    session.install(
+        "types-setuptools", "types-requests", "types-mock", "types-protobuf",
+    )
+    session.run("mypy", "google", "tests")
+
+
 @nox.session(python=DEFAULT_PYTHON_VERSION)
 def blacken(session):
     """Run black.