add mypy to pre-commit

.pre-commit-config.yaml

@@ -11,3 +11,7 @@ repos:
     rev: 5.12.0
     hooks:
     - id: isort
+  - repo: https://github.com/pre-commit/mirrors-mypy
+    rev: '9db9854e3041219b1eb619872a2dfaf58adfb20b'  # v1.9.0
+    hooks:
+    - id: mypy

mypy.ini

@@ -0,0 +1,52 @@
+[mypy]
+# start with an ideal: enable strict type-checking, then loosen in module-specific config
+# see https://mypy.readthedocs.io/en/stable/existing_code.html#introduce-stricter-options
+strict = True
+## BEGIN aspects of `strict` that could be loosened:
+# disallow_subclassing_any = False
+# warn_unused_configs = False
+# warn_redundant_casts = False
+# warn_unused_ignores = False
+# strict_equality = False
+# strict_concatenate = False
+# check_untyped_defs = False
+# disallow_untyped_decorators = False
+# disallow_any_generics = False
+# disallow_untyped_calls = False
+# disallow_incomplete_defs = False
+# disallow_untyped_defs = False
+# no_implicit_reexport = False
+# warn_return_any = False
+## END aspects of `strict`
+
+# prefer types that can be understood by reading code in only one place
+local_partial_types = True
+# avoid easily-avoidable dead code
+warn_unreachable = True
+
+###
+# module-specific config
+
+[mypy-addon_toolkit.*]
+## loosen strict:
+disallow_any_generics = False
+disallow_untyped_calls = False
+disallow_incomplete_defs = False
+disallow_untyped_defs = False
+
+[mypy-addon_service.*,app.*,manage]
+# got untyped dependencies -- this is fine
+ignore_missing_imports = True
+disable_error_code = import-untyped,import-not-found
+## loosen strict:
+disallow_subclassing_any = False
+disallow_untyped_decorators = False
+disallow_any_generics = False
+disallow_untyped_calls = False
+disallow_incomplete_defs = False
+disallow_untyped_defs = False
+warn_return_any = False
+
+[mypy-addon_service.migrations.*]
+strict = False
+disable_error_code = var-annotated

requirements/dev-requirements.txt

@@ -10,3 +10,6 @@ flake8
 black
 isort
 pre-commit
+
+# Type checking
+mypy