[Hotfix] Make Use class callable to resolve mypy type errors with And/Or

.github/workflows/python-test.yml

@@ -21,7 +21,7 @@ jobs:
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        pip install pytest
+        pip install pytest mypy
         if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
 
     - name: Run tests

schema/__init__.py

@@ -303,6 +303,15 @@ def __init__(
     def __repr__(self) -> str:
         return f"{self.__class__.__name__}({self._callable!r})"
 
+    def __call__(self, data: Any) -> Any:
+        """Make Use instances callable by delegating to the wrapped callable.
+
+        This allows Use to work properly with And, Or, and other combinators
+        that expect callable arguments, while maintaining the validate() method
+        for the validator pattern.
+        """
+        return self._callable(data)
+
     def validate(self, data: Any, **kwargs: Any) -> Any:
         try:
             return self._callable(data)

test_mypy_use_callable.py

@@ -0,0 +1,198 @@
+"""Test that mypy no longer reports "incompatible type Use" errors.
+
+This test actually runs mypy as a subprocess and verifies that the specific
+error about Use being incompatible with And/Or is NOT present.
+"""
+
+import shutil
+import subprocess
+import sys
+import tempfile
+from pathlib import Path
+
+import pytest
+
+
+# Check if mypy is available
+def is_mypy_available():
+    """Check if mypy is available in the environment."""
+    return shutil.which("mypy") is not None or _can_import_mypy()
+
+
+def _can_import_mypy():
+    """Check if mypy can be imported as a module."""
+    try:
+        __import__("mypy")
+        return True
+    except ImportError:
+        return False
+
+
+# Skip all tests in this module if mypy is not available
+pytestmark = pytest.mark.skipif(
+    not is_mypy_available(), reason="mypy is not available in the environment"
+)
+
+
+def test_mypy_use_with_and_no_error():
+    """Test that mypy doesn't report 'incompatible type Use' error with And."""
+    # Create a temporary test file with the problematic code
+    test_code = """
+from schema import And, Use
+
+# This used to fail with: Argument 2 to "And" has incompatible type "Use"
+schema = And(int, Use(int))
+"""
+
+    with tempfile.NamedTemporaryFile(mode="w", suffix=".py", delete=False) as f:
+        f.write(test_code)
+        temp_file = f.name
+
+    try:
+        # Run mypy on the test file
+        result = subprocess.run(
+            [sys.executable, "-m", "mypy", "--no-error-summary", temp_file],
+            capture_output=True,
+            text=True,
+        )
+
+        # Check that the specific error about Use is NOT present
+        output = result.stdout + result.stderr
+
+        # The error we're looking for (should NOT be present)
+        error_pattern = 'incompatible type "Use"'
+
+        assert (
+            error_pattern.lower() not in output.lower()
+        ), f"Found 'incompatible type Use' error in mypy output:\n{output}"
+
+        print("✓ mypy does not report 'incompatible type Use' error")
+
+    finally:
+        Path(temp_file).unlink(missing_ok=True)
+
+
+def test_mypy_use_with_or_no_error():
+    """Test that mypy doesn't report 'incompatible type Use' error with Or."""
+    test_code = """
+from schema import Or, Use
+
+# This used to fail with: Argument to "Or" has incompatible type "Use"
+schema = Or(Use(int), Use(float))
+"""
+
+    with tempfile.NamedTemporaryFile(mode="w", suffix=".py", delete=False) as f:
+        f.write(test_code)
+        temp_file = f.name
+
+    try:
+        result = subprocess.run(
+            [sys.executable, "-m", "mypy", "--no-error-summary", temp_file],
+            capture_output=True,
+            text=True,
+        )
+
+        output = result.stdout + result.stderr
+        error_pattern = 'incompatible type "Use"'
+
+        assert (
+            error_pattern.lower() not in output.lower()
+        ), f"Found 'incompatible type Use' error in mypy output:\n{output}"
+
+        print("✓ mypy does not report 'incompatible type Use' error with Or")
+
+    finally:
+        Path(temp_file).unlink(missing_ok=True)
+
+
+def test_mypy_use_with_and_complex_no_error():
+    """Test complex And/Or combinations with Use don't produce mypy errors."""
+    test_code = """
+from schema import And, Or, Use, Schema, Optional
+
+# Complex cases that used to fail
+schema1 = And(str, Use(int))
+schema2 = Or(int, Use(str))
+schema3 = Schema({
+    "age": And(Use(int), lambda n: 0 <= n <= 120),
+    "name": Use(str.title),
+    Optional("email"): Use(str.lower),
+})
+"""
+
+    with tempfile.NamedTemporaryFile(mode="w", suffix=".py", delete=False) as f:
+        f.write(test_code)
+        temp_file = f.name
+
+    try:
+        result = subprocess.run(
+            [sys.executable, "-m", "mypy", "--no-error-summary", temp_file],
+            capture_output=True,
+            text=True,
+        )
+
+        output = result.stdout + result.stderr
+        error_pattern = 'incompatible type "Use"'
+
+        assert (
+            error_pattern.lower() not in output.lower()
+        ), f"Found 'incompatible type Use' error in mypy output:\n{output}"
+
+        print("✓ mypy does not report 'incompatible type Use' error in complex schemas")
+
+    finally:
+        Path(temp_file).unlink(missing_ok=True)
+
+
+def test_mypy_use_callable_recognized():
+    """Test that Use is recognized as callable by mypy."""
+    test_code = """
+from schema import Use
+
+use_int = Use(int)
+
+# This should work - Use should be callable
+assert callable(use_int)
+result = use_int("123")
+"""
+
+    with tempfile.NamedTemporaryFile(mode="w", suffix=".py", delete=False) as f:
+        f.write(test_code)
+        temp_file = f.name
+
+    try:
+        result = subprocess.run(
+            [sys.executable, "-m", "mypy", "--no-error-summary", temp_file],
+            capture_output=True,
+            text=True,
+        )
+
+        output = result.stdout + result.stderr
+
+        # Should not have any "not callable" errors
+        assert (
+            "not callable" not in output.lower()
+        ), f"mypy thinks Use is not callable:\n{output}"
+
+        print("✓ mypy recognizes Use as callable")
+
+    finally:
+        Path(temp_file).unlink(missing_ok=True)
+
+
+if __name__ == "__main__":
+    if not is_mypy_available():
+        print("⚠️  mypy is not available in the environment.")
+        print("These tests require mypy to be installed.")
+        print("Install with: pip install mypy")
+        sys.exit(1)
+
+    print("Running mypy verification tests...\n")
+
+    test_mypy_use_with_and_no_error()
+    test_mypy_use_with_or_no_error()
+    test_mypy_use_with_and_complex_no_error()
+    test_mypy_use_callable_recognized()
+
+    print("\n✅ All mypy verification tests passed!")
+    print("The 'incompatible type Use' error has been fixed.")

tox.ini

@@ -11,12 +11,14 @@ commands = py.test
 recreate = true
 deps = pytest
        mock
+       mypy
 
 
 [testenv:py38]
 commands = py.test --doctest-glob=README.rst  # test documentation
 deps = pytest
        mock
+       mypy
 
 [testenv:checks]
 basepython=python3
@@ -32,3 +34,4 @@ deps = pytest
        pytest-cov
        coverage
        mock
+       mypy