Add type hints and mypy config

.github/workflows/build.yml

@@ -12,6 +12,19 @@ env:
   AWS_NO_SIGN_REQUEST: "1"
 
 jobs:
+  type-checking:
+    name: Run Type Checking
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/setup-python@v4
+        with:
+          python-version: "3.11"
+          cache: 'pip' # caching pip dependencies
+      - run: pip install -r requirements/requirements.txt -r requirements/test.txt -r requirements/dev.txt
+      - name: Run mypy
+        run: mypy
+
   # Increase rate limits for public registry
   amazon-ecr-auth:
     runs-on: ubuntu-latest

.pre-commit-config.yaml

@@ -28,3 +28,11 @@ repos:
       - id: cmake-lint
         args:
           - --suppress-decorations
+  - repo: https://github.com/pre-commit/mirrors-mypy
+    rev: v1.13.0
+    hooks:
+      - id: mypy
+        name: Check types with mypy
+        language: system
+        entry: build/venv/bin/mypy
+        pass_filenames: false

kart/__init__.py

@@ -12,7 +12,6 @@
 import importlib
 import logging
 import os
-import platform
 import sys
 
 L = logging.getLogger("kart.__init__")
@@ -40,17 +39,17 @@
 )
 
 try:
-    import _kart_env
+    import _kart_env  # type: ignore[import]
 
     L.debug("Found _kart_env configuration module")
 except ImportError:
     L.debug("No _kart_env configuration module found")
     _kart_env = None
 
 is_frozen = getattr(sys, "frozen", None) and hasattr(sys, "_MEIPASS")
-is_darwin = platform.system() == "Darwin"
-is_linux = platform.system() == "Linux"
-is_windows = platform.system() == "Windows"
+is_darwin = sys.platform == "darwin"
+is_linux = sys.platform == "linux"
+is_windows = sys.platform == "win32"
 
 if is_darwin:
     libsuffix = "dylib"
@@ -146,7 +145,7 @@ def _env_path(path):
 os.environ["PATH"] = (
     os.pathsep.join(path_extras) + os.pathsep + os.environ.get("PATH", "")
 )
-if is_windows:
+if sys.platform == "win32":
     os.add_dll_directory(prefix if is_frozen else os.path.join(prefix, "lib"))
     # FIXME: git2.dll is in the package directory, but isn't setup for ctypes to use
     _pygit2_spec = importlib.util.find_spec("pygit2")

kart/annotations/db.py

@@ -2,7 +2,7 @@
 import json
 import logging
 import threading
-
+from typing import TypeAlias
 import sqlalchemy
 
 from kart.sqlalchemy.sqlite import sqlite_engine
@@ -13,7 +13,9 @@
 from sqlalchemy.schema import CreateTable
 
 L = logging.getLogger(__name__)
-Base = declarative_base()
+
+# TODO: remove this type ignore when we upgrade sqlalchemy to 2.0 and replace with DeclarativeBase
+Base: TypeAlias = declarative_base()  # type: ignore[valid-type]
 
 
 class KartAnnotation(Base):

kart/apply.py

@@ -370,7 +370,7 @@ def apply_patch(
     "--ref",
     default="HEAD",
     help="Which ref to apply the patch onto.",
-    shell_complete=ref_completer,
+    shell_complete=ref_completer,  # type: ignore[call-arg]
 )
 @click.option(
     "--amend",