add type checker

Author: GiovanniCanali

pina/type_checker.py

@@ -0,0 +1,93 @@
+"""Module for enforcing type hints in Python functions."""
+
+import inspect
+import typing
+import logging
+
+
+def enforce_types(func):
+    """
+    Function decorator to enforce type hints at runtime.
+
+    This decorator checks the types of the arguments and of the return value of
+    the decorated function against the type hints specified in the function
+    signature. If the types do not match, a TypeError is raised.
+    Type checking is only performed when the logging level is set to `DEBUG`.
+
+    :param Callable func: The function to be decorated.
+    :return: The decorated function with enforced type hints.
+    :rtype: Callable
+
+    :Example:
+
+    >>> @enforce_types
+        def dummy_function(a: int, b: float) -> float:
+        ... return a+b
+
+        # This always works.
+        dummy_function(1, 2.0)
+
+        # This raises a TypeError for the second argument, if logging is set to
+        # `DEBUG`.
+        dummy_function(1, "Hello, world!")
+
+
+    >>> @enforce_types
+        def dummy_function2(a: int, right: bool) -> float:
+        ... if right:
+        ...     return float(a)
+        ... else:
+        ...     return "Hello, world!"
+
+        # This always works.
+        dummy_function2(1, right=True)
+
+        # This raises a TypeError for the return value if logging is set to
+        # `DEBUG`.
+        dummy_function2(1, right=False)
+    """
+
+    def wrapper(*args, **kwargs):
+        """
+        Wrapper function to enforce type hints.
+
+        :param tuple args: Positional arguments passed to the function.
+        :param dict kwargs: Keyword arguments passed to the function.
+        :raises TypeError: If the argument or return type does not match the
+            specified type hints.
+        :return: The result of the decorated function.
+        :rtype: Any
+        """
+        level = logging.getLevelName(logging.getLogger().getEffectiveLevel())
+
+        # Enforce type hints only in debug mode
+        if level != "DEBUG":
+            return func(*args, **kwargs)
+
+        # Get the type hints for the function arguments
+        hints = typing.get_type_hints(func)
+        sig = inspect.signature(func)
+        bound = sig.bind(*args, **kwargs)
+        bound.apply_defaults()
+
+        for arg_name, arg_value in bound.arguments.items():
+            expected_type = hints.get(arg_name)
+            if expected_type and not isinstance(arg_value, expected_type):
+                raise TypeError(
+                    f"Argument '{arg_name}' must be {expected_type.__name__}, "
+                    f"but got {type(arg_value).__name__}!"
+                )
+
+        # Get the type hints for the return values
+        return_type = hints.get("return")
+        result = func(*args, **kwargs)
+
+        if return_type and not isinstance(result, return_type):
+            raise TypeError(
+                f"Return value must be {return_type.__name__}, "
+                f"but got {type(result).__name__}!"
+            )
+
+        return result
+
+    return wrapper

tests/test_type_checker.py

@@ -0,0 +1,55 @@
+import pytest
+import logging
+import math
+from pina.type_checker import enforce_types
+
+
+# Definition of a test function for arguments
+@enforce_types
+def foo_function1(a: int, b: float) -> float:
+    return a + b
+
+
+# Definition of a test function for return values
+@enforce_types
+def foo_function2(a: int, right: bool) -> float:
+    if right:
+        return float(a)
+    else:
+        return "Hello, world!"
+
+
+def test_argument_type_checking():
+
+    # Setting logging level to INFO, which should not trigger type checking
+    logging.getLogger().setLevel(logging.INFO)
+
+    # Both should work, even if the arguments are not of the expected type
+    assert math.isclose(foo_function1(a=1, b=2.0), 3.0)
+    assert math.isclose(foo_function1(a=1, b=2), 3.0)
+
+    # Setting logging level to DEBUG, which should trigger type checking
+    logging.getLogger().setLevel(logging.DEBUG)
+
+    # The second should fail, as the second argument is an int
+    assert math.isclose(foo_function1(a=1, b=2.0), 3.0)
+    with pytest.raises(TypeError):
+        foo_function1(a=1, b=2)
+
+
+def test_return_type_checking():
+
+    # Setting logging level to INFO, which should not trigger type checking
+    logging.getLogger().setLevel(logging.INFO)
+
+    # Both should work, even if the return value is not of the expected type
+    assert math.isclose(foo_function2(a=1, right=True), 1.0)
+    assert foo_function2(a=1, right=False) == "Hello, world!"
+
+    # Setting logging level to DEBUG, which should trigger type checking
+    logging.getLogger().setLevel(logging.DEBUG)
+
+    # The second should fail, as the return value is a string
+    assert math.isclose(foo_function2(a=1, right=True), 1.0)
+    with pytest.raises(TypeError):
+        foo_function2(a=1, right=False)