Initial typing support

This enables type checking in CI and marks the project as typed.

.github/workflows/tests.yaml

@@ -31,6 +31,7 @@ jobs:
           - {name: '3.7', python: '3.7', os: ubuntu-latest, tox: py37}
           - {name: '3.6', python: '3.6', os: ubuntu-latest, tox: py36}
           - {name: 'PyPy', python: pypy3, os: ubuntu-latest, tox: pypy3}
+          - {name: Typing, python: '3.9', os: ubuntu-latest, tox: typing}
     steps:
       - uses: actions/checkout@v2
       - uses: actions/setup-python@v2

MANIFEST.in

@@ -7,4 +7,5 @@ graft docs
 prune docs/_build
 graft examples
 graft tests
+include src/flask/py.typed
 global-exclude *.pyc

requirements/typing.in

+mypy

requirements/typing.txt

+#
+# This file is autogenerated by pip-compile
+# To update, run:
+#
+#    pip-compile requirements/typing.in
+#
+mypy-extensions==0.4.3
+    # via mypy
+mypy==0.812
+    # via -r requirements/typing.in
+typed-ast==1.4.3
+    # via mypy
+typing-extensions==3.7.4.3
+    # via mypy

setup.cfg

@@ -85,3 +85,30 @@ max-line-length = 80
 per-file-ignores =
     # __init__ module exports names
     src/flask/__init__.py: F401
+
+[mypy]
+files = src/flask
+python_version = 3.6
+allow_redefinition = True
+disallow_subclassing_any = True
+# disallow_untyped_calls = True
+# disallow_untyped_defs = True
+# disallow_incomplete_defs = True
+no_implicit_optional = True
+local_partial_types = True
+# no_implicit_reexport = True
+strict_equality = True
+warn_redundant_casts = True
+warn_unused_configs = True
+warn_unused_ignores = True
+# warn_return_any = True
+# warn_unreachable = True
+
+[mypy-asgiref.*]
+ignore_missing_imports = True
+
+[mypy-blinker.*]
+ignore_missing_imports = True
+
+[mypy-dotenv.*]
+ignore_missing_imports = True

tox.ini

@@ -2,6 +2,7 @@
 envlist =
     py{39,38,37,36,py3}
     style
+    typing
     docs
 skip_missing_interpreters = true
 
@@ -24,6 +25,10 @@ deps = pre-commit
 skip_install = true
 commands = pre-commit run --all-files --show-diff-on-failure
 
+[testenv:typing]
+deps = -r requirements/typing.txt
+commands = mypy
+
 [testenv:docs]
 deps =
     -r requirements/docs.txt