An example mypy configuration

.github/workflows/type_checking.yml

@@ -0,0 +1,26 @@
+name: Type checking
+
+on:
+  push:
+    paths:
+      - '*.py'
+
+jobs:
+  mypy:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Setup Python
+        uses: actions/setup-python@v1
+        with:
+          python-version: 3.7.4
+          architecture: x64
+      - name: Checkout
+        uses: actions/checkout@v1
+      - name: Install mypy
+        run: pip install mypy
+      - name: Run mypy
+        uses: sasanquaneuf/mypy-github-action@releases/v1
+        with:
+          checkName: 'mypy'   # NOTE: This needs to be the same as the job name
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

corehq/motech/serializers.py

@@ -15,7 +15,7 @@
 """
 import datetime
 import re
-from typing import Any
+from typing import Any, Callable, Optional
 
 from dateutil import parser as dateutil_parser
 
@@ -101,7 +101,7 @@ def to_datetime_str(value):
         return value.isoformat(timespec='milliseconds')
 
 
-serializers = {
+serializers: dict[tuple[Optional[str], Optional[str]], Callable] = {
     # (from_data_type, to_data_type): function
     (None, COMMCARE_DATA_TYPE_BOOLEAN): to_boolean,
     (None, COMMCARE_DATA_TYPE_DECIMAL): to_decimal,

corehq/motech/value_source.py

@@ -1,4 +1,7 @@
-from typing import Any, Dict, List, Optional, Tuple, Union
+from __future__ import annotations
+
+from dataclasses import dataclass, field
+from typing import Any, Dict, List, Optional, Tuple, Type, TypeVar, Union
 
 import attr
 from jsonobject.containers import JsonDict
@@ -27,32 +30,34 @@
 from .serializers import serializers
 from .utils import simplify_list
 
+T = TypeVar('T')
 
-@attr.s
+
+@dataclass
 class CaseTriggerInfo:
-    domain = attr.ib()
-    case_id = attr.ib()
-    type = attr.ib(default=None)
-    name = attr.ib(default=None)
-    owner_id = attr.ib(default=None)
-    modified_by = attr.ib(default=None)
-    updates = attr.ib(factory=dict)
-    created = attr.ib(default=None)
-    closed = attr.ib(default=None)
-    extra_fields = attr.ib(factory=dict)
-    form_question_values = attr.ib(factory=dict)
+    domain: str
+    case_id: str
+    type: Optional[str] = None
+    name: Optional[str] = None
+    owner_id: Optional[str] = None
+    modified_by: Optional[str] = None
+    updates: dict[str, Any] = field(default_factory=dict)
+    created: Optional[bool] = None
+    closed: Optional[bool] = None
+    extra_fields: dict[str, Any] = field(default_factory=dict)
+    form_question_values: dict[str, Any] = field(default_factory=dict)
 
     def __str__(self):
         if self.name:
             return f'<CaseTriggerInfo {self.case_id} {self.name!r}>'
         return f"<CaseTriggerInfo {self.case_id}>"
 
 
-def recurse_subclasses(cls):
-    return (
-        cls.__subclasses__()
-        + [subsub for sub in cls.__subclasses__() for subsub in recurse_subclasses(sub)]
-    )
+def recurse_subclasses(cls: Type[T]) -> list[Type[T]]:
+    return cls.__subclasses__() + [
+        subsub for sub in cls.__subclasses__()
+        for subsub in recurse_subclasses(sub)
+    ]
 
 
 @attr.s(auto_attribs=True, kw_only=True)
@@ -86,7 +91,7 @@ class ValueSource:
     jsonpath: Optional[str] = None
 
     @classmethod
-    def wrap(cls, data: dict):
+    def wrap(cls, data: dict) -> ValueSource:
         """
         Allows us to duck-type JsonObject, and useful for doing
         pre-instantiation transforms / dropping unwanted attributes.

mypy.ini

@@ -0,0 +1,20 @@
+# Global options:
+
+[mypy]
+python_version = 3.9
+ignore_missing_imports = True
+follow_imports = silent
+
+disallow_subclassing_any = True
+warn_return_any = True
+
+warn_redundant_casts = True
+warn_unused_ignores = True
+warn_unused_configs = True
+show_error_codes = True
+
+# Per-module options:
+
+[corehq.motech.value_source]
+disallow_untyped_defs = True
+disallow_any_generics = True

mypy_typed_modules.txt

@@ -0,0 +1 @@
+corehq/motech/value_source.py

requirements/dev-requirements.txt

@@ -334,8 +334,12 @@ matplotlib-inline==0.1.3
     # via ipython
 mccabe==0.6.1
     # via flake8
+mypy==0.931
+    # via -r test-requirements.in
 mypy-extensions==0.4.3
-    # via black
+    # via
+    #   black
+    #   mypy
 nose==1.3.7
     # via
     #   -r test-requirements.in
@@ -633,7 +637,9 @@ tinys3==0.1.12
 toml==0.10.2
     # via pep517
 tomli==2.0.0
-    # via black
+    # via
+    #   black
+    #   mypy
 toposort==1.7
     # via -r base-requirements.in
 traitlets==5.1.1
@@ -647,7 +653,9 @@ turn-python==0.0.1
 twilio==6.5.1
     # via -r base-requirements.in
 typing-extensions==4.1.1
-    # via black
+    # via
+    #   black
+    #   mypy
 ua-parser==0.10.0
     # via user-agents
 unidecode==1.2.0

requirements/test-requirements.in

@@ -3,6 +3,7 @@
 beautifulsoup4
 django-nose @ https://github.com/dimagi/django-nose/raw/fast-first-1.4.6.1/releases/django_nose-1.4.6.1-py2.py3-none-any.whl
 fakecouch
+mypy
 nose
 nose-exclude
 pip-tools>6.4.0

requirements/test-requirements.txt

@@ -284,6 +284,10 @@ markupsafe==1.1.1
     # via
     #   jinja2
     #   mako
+mypy==0.931
+    # via -r test-requirements.in
+mypy-extensions==0.4.3
+    # via mypy
 nose==1.3.7
     # via
     #   -r test-requirements.in
@@ -512,6 +516,8 @@ tinys3==0.1.12
     # via -r base-requirements.in
 toml==0.10.2
     # via pep517
+tomli==2.0.1
+    # via mypy
 toposort==1.7
     # via -r base-requirements.in
 tropo-webapi-python==0.1.3
@@ -520,6 +526,8 @@ turn-python==0.0.1
     # via -r base-requirements.in
 twilio==6.5.1
     # via -r base-requirements.in
+typing-extensions==4.1.1
+    # via mypy
 ua-parser==0.10.0
     # via user-agents
 unidecode==1.2.0