feat: add 'py.typed' declaration (#73)

Check typing under CI using new 'mypy' nox session.

mypy.ini

@@ -0,0 +1,3 @@
+[mypy]
+python_version = 3.6
+exclude = tests/unit/resources/

noxfile.py

@@ -27,6 +27,7 @@
     "lint",
     "blacken",
     "lint_setup_py",
+    "mypy",
     "unit",
     "check_lower_bounds"
 ]
@@ -74,6 +75,18 @@ def lint_setup_py(session):
     session.run("python", "setup.py", "check", "--restructuredtext", "--strict")
 
 
+@nox.session(python="3.6")
+def mypy(session):
+    """Verify type hints are mypy compatible."""
+    session.install("-e", ".")
+    session.install(
+        "mypy",
+        "types-mock",
+        "types-setuptools",
+    )
+    session.run("mypy", "test_utils/", "tests/")
+
+
 @nox.session(python=["3.6", "3.7", "3.8", "3.9", "3.10"])
 def unit(session):
     constraints_path = str(

test_utils/lower_bound_checker/lower_bound_checker.py

@@ -33,7 +33,8 @@ def _get_package_requirements(package_name: str) -> List[Requirement]:
         List[pkg_resources.Requirement]: A list of package requirements and extras.
     """
     dist = pkg_resources.get_distribution(package_name)
-    requirements = [Requirement(str(r)) for r in dist.requires(extras=dist.extras)]
+    extras = tuple(dist.extras)
+    requirements = [Requirement(str(r)) for r in dist.requires(extras=extras)]
 
     return requirements
 

test_utils/prefixer.py

@@ -16,6 +16,7 @@
 import random
 import re
 
+from typing import Union
 
 _RESOURCE_DATE_FORMAT = "%Y%m%d%H%M%S"
 _RESOURCE_DATE_LENGTH = 4 + 2 + 2 + 2 + 2 + 2
@@ -61,7 +62,7 @@ def create_prefix(self) -> str:
         random_string = hex(random.randrange(0x1000000))[2:]
         return f"{self._prefix}{self._separator}{timestamp}{self._separator}{random_string}"
 
-    def _name_to_date(self, resource_name: str) -> datetime.datetime:
+    def _name_to_date(self, resource_name: str) -> Union[datetime.datetime, None]:
         start_date = len(self._prefix) + len(self._separator)
         date_string = resource_name[start_date : start_date + _RESOURCE_DATE_LENGTH]
         try:

test_utils/py.typed

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

test_utils/system.py

@@ -17,8 +17,8 @@
 import sys
 import time
 
-import google.auth.credentials
-from google.auth.environment_vars import CREDENTIALS as TEST_CREDENTIALS
+import google.auth.credentials  # type: ignore
+from google.auth.environment_vars import CREDENTIALS as TEST_CREDENTIALS  # type: ignore
 
 
 # From shell environ. May be None.

test_utils/vpcsc_config.py

@@ -16,7 +16,7 @@
 
 import os
 
-import pytest
+import pytest  # type: ignore
 
 
 INSIDE_VPCSC_ENVVAR = "GOOGLE_CLOUD_TESTS_IN_VPCSC"

tests/unit/test_lower_bound_checker.py

@@ -19,7 +19,7 @@
 from typing import List
 
 from click.testing import CliRunner
-import pytest
+import pytest  # type: ignore
 
 from test_utils.lower_bound_checker import lower_bound_checker
 
@@ -45,7 +45,7 @@ def parse_error_msg(msg: str) -> List[str]:
     reqs = []
 
     if match:
-        reqs = match.groups(1)[0].split(",")
+        reqs = match.groups(1)[0].split(",")  # type: ignore
         reqs = [r.strip().replace("'", "").replace('"', "") for r in reqs]
 
     return reqs

tests/unit/test_orchestrate.py

@@ -18,9 +18,9 @@
 try:
     from unittest import mock
 except ImportError:  # pragma: NO PY3 COVER
-    import mock
+    import mock  # type: ignore
 
-import pytest
+import pytest  # type: ignore
 
 from test_utils import orchestrate
 

tests/unit/test_prefixer.py

@@ -15,7 +15,7 @@
 import datetime
 import re
 
-import pytest
+import pytest  # type: ignore
 
 import test_utils.prefixer