feat: allow mypy to be used in a Stop hook

Author: joshuanapoli

.claude/settings.json

@@ -21,6 +21,10 @@
             "type": "command",
             "command": "poetry run python-claude ruff check"
           },
+          {
+            "type": "command",
+            "command": "poetry run python-claude mypy"
+          },
           {
             "type": "command",
             "command": "poetry run python-claude pytest"

README.md

@@ -31,7 +31,7 @@ This package provides hooks that can be used with Claude Code's hook system.
 
 - `edited` - Tracks edited Python files for deferred processing
 - `git status` - Shows git status
-- `mypy` - Runs mypy type checking on edited files
+- `mypy` - Runs mypy type checking on edited files when used as a PostToolUse hook or all files when used as a Stop hook
 - `pytest` - Runs pytest
 - `ruff check` - Runs ruff check on collected files with auto-fix
 - `ruff format` - Runs ruff format on edited files
@@ -65,6 +65,10 @@ Add hooks to your Claude Code settings.json:
             "type": "command",
             "command": "poetry run python-claude ruff check"
           },
+          {
+            "type": "command",
+            "command": "poetry run python-claude mypy"
+          },
           {
             "type": "command",
             "command": "poetry run python-claude pytest"

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "python-claude"
-version = "0.1.1"
+version = "0.2.0"
 description = "Python hooks for Claude Code"
 authors = [{name = "CVector", email = "support@cvector.com"}]
 readme = "README.md"

src/python_claude/hooks/mypy_hook.py

@@ -15,16 +15,28 @@ def __init__(self, hook_input: HookInput | None = None) -> None:
         super().__init__(hook_input)
 
     def run(self) -> int:
-        """Run mypy on the edited file if it's a Python file."""
+        """Run mypy on the edited file or entire project.
+
+        If file_path is provided and is a Python file, run mypy on that file.
+        If no file_path is provided (e.g., Stop hook), run mypy on entire project.
+        """
         file_path = self.input.file_path
-        if not file_path or not self.is_python_file(file_path):
-            return 0
 
-        self.log(file_path)
+        # Determine what to type check
+        if file_path:
+            # File path provided - check if it's a Python file
+            if not self.is_python_file(file_path):
+                return 0
+            mypy_target = file_path
+        else:
+            # No file path (Stop hook) - check entire project
+            mypy_target = "."
+
+        self.log(mypy_target)
 
         # mypy writes errors to stdout, but only stderr is fed back to Claude
         result = subprocess.run(
-            ["poetry", "run", "mypy", file_path],
+            ["poetry", "run", "mypy", mypy_target],
             cwd=self.project_dir,
             stdout=sys.stderr,  # Redirect stdout to stderr for Claude
         )

tests/test_mypy_hook.py

@@ -0,0 +1,134 @@
+"""Tests for MypyHook."""
+
+import os
+from pathlib import Path
+from unittest.mock import MagicMock, patch
+
+from python_claude.hooks.base import HookInput
+from python_claude.hooks.mypy_hook import MypyHook
+
+
+class TestMypyHook:
+    def test_python_file_success(self, tmp_path: Path) -> None:
+        """Test mypy succeeds on a Python file."""
+        hook_input = HookInput(
+            session_id=None,
+            tool_input={"file_path": "/path/to/file.py"},
+            raw={},
+        )
+        with patch.dict(os.environ, {"CLAUDE_PROJECT_DIR": str(tmp_path)}):
+            hook = MypyHook(hook_input)
+            mock_result = MagicMock()
+            mock_result.returncode = 0
+            with patch("subprocess.run", return_value=mock_result) as mock_run:
+                exit_code = hook.run()
+                assert exit_code == 0
+                mock_run.assert_called_once()
+                # Verify it ran mypy on the specific file
+                call_args = mock_run.call_args
+                assert call_args[0][0] == ["poetry", "run", "mypy", "/path/to/file.py"]
+
+    def test_python_file_type_errors(self, tmp_path: Path) -> None:
+        """Test mypy type errors (exit 1) are transformed to exit code 2."""
+        hook_input = HookInput(
+            session_id=None,
+            tool_input={"file_path": "/path/to/file.py"},
+            raw={},
+        )
+        with patch.dict(os.environ, {"CLAUDE_PROJECT_DIR": str(tmp_path)}):
+            hook = MypyHook(hook_input)
+            mock_result = MagicMock()
+            mock_result.returncode = 1
+            with patch("subprocess.run", return_value=mock_result):
+                exit_code = hook.run()
+                assert exit_code == 2
+
+    def test_python_file_other_error(self, tmp_path: Path) -> None:
+        """Test other mypy errors are passed through unchanged."""
+        hook_input = HookInput(
+            session_id=None,
+            tool_input={"file_path": "/path/to/file.py"},
+            raw={},
+        )
+        with patch.dict(os.environ, {"CLAUDE_PROJECT_DIR": str(tmp_path)}):
+            hook = MypyHook(hook_input)
+            mock_result = MagicMock()
+            mock_result.returncode = 3
+            with patch("subprocess.run", return_value=mock_result):
+                exit_code = hook.run()
+                assert exit_code == 3
+
+    def test_non_python_file(self, tmp_path: Path) -> None:
+        """Test non-Python files are skipped."""
+        hook_input = HookInput(
+            session_id=None,
+            tool_input={"file_path": "/path/to/file.txt"},
+            raw={},
+        )
+        with patch.dict(os.environ, {"CLAUDE_PROJECT_DIR": str(tmp_path)}):
+            hook = MypyHook(hook_input)
+            with patch("subprocess.run") as mock_run:
+                exit_code = hook.run()
+                assert exit_code == 0
+                # Verify subprocess was not called
+                mock_run.assert_not_called()
+
+    def test_stop_hook_no_file_path_success(self, tmp_path: Path) -> None:
+        """Test Stop hook (no file_path) runs mypy on entire project."""
+        hook_input = HookInput(
+            session_id="abc123",
+            tool_input={},
+            raw={
+                "session_id": "abc123",
+                "hook_event_name": "Stop",
+                "stop_hook_active": True,
+            },
+        )
+        with patch.dict(os.environ, {"CLAUDE_PROJECT_DIR": str(tmp_path)}):
+            hook = MypyHook(hook_input)
+            mock_result = MagicMock()
+            mock_result.returncode = 0
+            with patch("subprocess.run", return_value=mock_result) as mock_run:
+                exit_code = hook.run()
+                assert exit_code == 0
+                mock_run.assert_called_once()
+                # Verify it ran mypy on current directory
+                call_args = mock_run.call_args
+                assert call_args[0][0] == ["poetry", "run", "mypy", "."]
+
+    def test_stop_hook_type_errors(self, tmp_path: Path) -> None:
+        """Test Stop hook with type errors (exit 1) transforms to exit code 2."""
+        hook_input = HookInput(
+            session_id="abc123",
+            tool_input={},
+            raw={
+                "session_id": "abc123",
+                "hook_event_name": "Stop",
+                "stop_hook_active": True,
+            },
+        )
+        with patch.dict(os.environ, {"CLAUDE_PROJECT_DIR": str(tmp_path)}):
+            hook = MypyHook(hook_input)
+            mock_result = MagicMock()
+            mock_result.returncode = 1
+            with patch("subprocess.run", return_value=mock_result):
+                exit_code = hook.run()
+                assert exit_code == 2
+
+    def test_empty_file_path_runs_full_check(self, tmp_path: Path) -> None:
+        """Test empty string file_path is treated as Stop hook."""
+        hook_input = HookInput(
+            session_id=None,
+            tool_input={"file_path": ""},
+            raw={},
+        )
+        with patch.dict(os.environ, {"CLAUDE_PROJECT_DIR": str(tmp_path)}):
+            hook = MypyHook(hook_input)
+            mock_result = MagicMock()
+            mock_result.returncode = 0
+            with patch("subprocess.run", return_value=mock_result) as mock_run:
+                exit_code = hook.run()
+                assert exit_code == 0
+                # Verify it ran mypy on current directory
+                call_args = mock_run.call_args
+                assert call_args[0][0] == ["poetry", "run", "mypy", "."]