Add mypy

.envrc

@@ -1 +1,2 @@
 use flake
+watch_file pyproject.toml

flake.nix

@@ -66,11 +66,12 @@
               touch $out
             '';
           in
-          {
-            pytest = mkCheck "pytest" "pytest --workers auto";
-            treefmt = mkCheck "treefmt" "treefmt --no-cache --fail-on-change";
-            deadnix = mkCheck "deadnix" "deadnix --fail";
-            statix = mkCheck "statix" "statix check";
+          lib.mapAttrs mkCheck {
+            pytest = "pytest --workers auto";
+            treefmt = "treefmt --no-cache --fail-on-change";
+            deadnix = "deadnix --fail";
+            statix = "statix check";
+            mypy = "mypy .";
           };
 
       });

pyproject.toml

@@ -19,4 +19,5 @@ dev = [
     "pytest>=7.2.1",
     "pytest-parallel>=0.1.1",
     "black>=23.7.0",
+    "mypy>=1.4.1",
 ]

tests/test_nix.py

@@ -1,9 +1,9 @@
 from typing import (
     Iterator,
     Optional,
-    Tuple,
     Dict,
     List,
+    cast,
     Set,
     Any,
 )
@@ -16,7 +16,7 @@ def assert_deepequals(
     a: Any,
     b: Any,
     ignore_paths: Optional[Set[str]] = None,
-    _path: Optional[Tuple[str]] = None,
+    _path: Optional[tuple[str]] = None,
 ):
     """Compare objects a and b keeping track of object path for error reporting.
 
@@ -37,7 +37,7 @@ def assert_deepequals(
     }, ignore_paths=set(["metadata.poetry-version"]))
     """
 
-    _path = _path if _path else tuple()
+    _path = cast(tuple[str], (_path if _path else tuple()))
     ignore_paths = ignore_paths if ignore_paths else set()
     path = ".".join(_path)
     err = ValueError("{}: {} != {}".format(path, a, b))