feat: type hinting more code with mypy

mypy.ini

@@ -3,4 +3,16 @@ follow_imports = silent
 ignore_missing_imports = True
 allow_untyped_globals = True
 exclude = tests
-files = openedx/core/djangoapps/content/learning_sequences/,openedx/core/types
+plugins =
+    mypy_django_plugin.main,
+    mypy_drf_plugin.main
+files =
+    openedx/core/djangoapps/content/learning_sequences/,
+    openedx/core/djangoapps/content_staging,
+    openedx/core/djangoapps/content_libraries,
+    openedx/core/djangoapps/xblock,
+    openedx/core/types
+
+[mypy.plugins.django-stubs]
+# content_staging only works with CMS; others work with either, so we run mypy with CMS settings.
+django_settings_module = "cms.envs.test"

requirements/constraints.txt

@@ -113,3 +113,8 @@ djangorestframework<3.15.0
 
 # tests failing with greater version. Fix this in separate ticket.
 pillow<10.0.0
+
+# The version of django-stubs we can use depends on which Django release we're using
+# 1.16.0 works with Django 3.2 through 4.1
+django-stubs==1.16.0
+djangorestframework-stubs==3.14.0  # Pinned to match django-stubs. Remove this when we can remove the above pin.

requirements/edx/development.in

@@ -16,6 +16,8 @@
 
 click                                   # Used for perf_tests utilities in modulestore
 django-debug-toolbar                    # A set of panels that display debug information about the current request/response
+django-stubs                            # Typing stubs for Django, so it works with mypy
+djangorestframework-stubs               # Typing stubs for DRF
 mypy                                    # static type checking
 pywatchman                              # More efficient checking for runserver reload trigger events
 vulture                                 # Detects possible dead/unused code, used in scripts/find-dead-code.sh

requirements/edx/development.txt

@@ -358,6 +358,8 @@ django==3.2.20
     #   django-splash
     #   django-statici18n
     #   django-storages
+    #   django-stubs
+    #   django-stubs-ext
     #   django-user-tasks
     #   djangorestframework
     #   drf-jwt
@@ -576,6 +578,13 @@ django-storages==1.9.1
     #   -r requirements/edx/doc.txt
     #   -r requirements/edx/testing.txt
     #   edxval
+django-stubs==1.16.0
+    # via
+    #   -c requirements/edx/../constraints.txt
+    #   -r requirements/edx/development.in
+    #   djangorestframework-stubs
+django-stubs-ext==4.2.2
+    # via django-stubs
 django-user-tasks==3.0.0
     # via
     #   -r requirements/edx/doc.txt
@@ -618,6 +627,10 @@ djangorestframework==3.14.0
     #   openedx-blockstore
     #   ora2
     #   super-csv
+djangorestframework-stubs==3.14.0
+    # via
+    #   -c requirements/edx/../constraints.txt
+    #   -r requirements/edx/development.in
 djangorestframework-xml==2.0.0
     # via
     #   -r requirements/edx/doc.txt
@@ -1226,7 +1239,10 @@ multidict==6.0.4
     #   aiohttp
     #   yarl
 mypy==1.4.1
-    # via -r requirements/edx/development.in
+    # via
+    #   -r requirements/edx/development.in
+    #   django-stubs
+    #   djangorestframework-stubs
 mypy-extensions==1.0.0
     # via mypy
 mysqlclient==2.2.0
@@ -1721,6 +1737,7 @@ requests==2.31.0
     #   analytics-python
     #   coreapi
     #   django-oauth-toolkit
+    #   djangorestframework-stubs
     #   edx-bulk-grades
     #   edx-drf-extensions
     #   edx-enterprise
@@ -2012,6 +2029,7 @@ tomli==2.0.1
     #   -r requirements/edx/testing.txt
     #   build
     #   coverage
+    #   django-stubs
     #   import-linter
     #   mypy
     #   pip-tools
@@ -2043,6 +2061,9 @@ typing-extensions==4.7.1
     #   asgiref
     #   astroid
     #   django-countries
+    #   django-stubs
+    #   django-stubs-ext
+    #   djangorestframework-stubs
     #   faker
     #   fastapi
     #   grimp