Add support for PEP 561

setup.cfg

@@ -44,6 +44,7 @@ install_requires=
     keyring >= 15.1
 setup_requires =
     setuptools_scm >= 1.15
+zip_safe = False
 
 [options.entry_points]
 twine.registered_commands =
@@ -52,3 +53,6 @@ twine.registered_commands =
     register = twine.commands.register:main
 console_scripts =
     twine = twine.__main__:main
+
+[options.package_data]
+twine = py.typed

tests/test_mypy_integration.py

@@ -0,0 +1,65 @@
+"""
+Verify that twine passes type-checking when used as a library.
+
+https://mypy.readthedocs.io/en/stable/installed_packages.html#making-pep-561-compatible-packages
+"""
+import subprocess
+import textwrap
+
+import pytest
+
+
+@pytest.fixture
+def example_py(tmpdir, monkeypatch):
+    # Changing directory so that mypy uses installed twine, instead of source
+    monkeypatch.chdir(tmpdir)
+    return tmpdir / "example.py"
+
+
+def test_no_missing_import(example_py):
+    example_py.write("""import twine""")
+
+    subprocess.run(["mypy", "--strict", example_py], check=True)
+
+
+def test_type_error_for_command(example_py):
+    example_py.write(
+        textwrap.dedent(
+            """
+            from twine.commands import check
+
+            check.check('example.pkg')
+            """
+        )
+    )
+
+    with pytest.raises(subprocess.CalledProcessError) as excinfo:
+        subprocess.run(
+            ["mypy", "--strict", example_py], check=True, stdout=subprocess.PIPE
+        )
+
+    assert b"1 error in 1 file" in excinfo.value.output
+    assert (
+        b'"check" has incompatible type "str"; expected "List[str]"'
+        in excinfo.value.output
+    )
+
+
+def test_type_error_for_class(example_py):
+    example_py.write(
+        textwrap.dedent(
+            """
+            from twine import repository
+
+            repo = repository.Repository()
+            """
+        )
+    )
+
+    with pytest.raises(subprocess.CalledProcessError) as excinfo:
+        subprocess.run(
+            ["mypy", "--strict", example_py], check=True, stdout=subprocess.PIPE
+        )
+
+    assert b"1 error in 1 file" in excinfo.value.output
+    assert b'Too few arguments for "Repository"' in excinfo.value.output

tox.ini

@@ -11,6 +11,7 @@ deps =
     portend
     pytest-services
     munch
+    mypy
 commands =
     coverage run --source twine -m pytest {posargs:tests}
     coverage report -m