Reject non-boolean point-set reflection flags

src/pyrecest/utils/point_set_registration.py

@@ -262,6 +262,22 @@ def _validate_positive_integer(value, name: str, *, minimum: int = 1) -> int:
     return value_int
 
 
+def _validate_boolean_flag(value, name: str) -> bool:
+    """Return a real boolean flag without accepting merely truthy values."""
+    error_message = f"{name} must be a boolean."
+    if np.ma.is_masked(value):
+        raise TypeError(error_message)
+    if isinstance(value, (bool, np.bool_)):
+        return bool(value)
+    try:
+        value_array = np.asarray(value)
+    except (TypeError, ValueError, RuntimeError, OverflowError) as exc:
+        raise TypeError(error_message) from exc
+    if value_array.shape == () and value_array.dtype == np.bool_:
+        return bool(value_array.item())
+    raise TypeError(error_message)
+
+
 def estimate_transform(  # pylint: disable=too-many-locals
     source_points,
     target_points,
@@ -289,6 +305,7 @@ def estimate_transform(  # pylint: disable=too-many-locals
             "estimate_transform is not supported on the JAX backend."
         )
 
+    allow_reflection = _validate_boolean_flag(allow_reflection, "allow_reflection")
     source, target = _validate_pair(source_points, target_points)
     n_points, dim = source.shape
     min_matches = _minimum_required_matches(model, dim)
@@ -405,6 +422,7 @@ def joint_registration_assignment(  # pylint: disable=too-many-arguments,too-man
             "joint_registration_assignment is not supported on the JAX backend."
         )
 
+    allow_reflection = _validate_boolean_flag(allow_reflection, "allow_reflection")
     max_iterations = _validate_positive_integer(max_iterations, "max_iterations")
 
     reference = _as_point_array(reference_points)

tests/test_point_set_registration_reflection_flag.py

@@ -0,0 +1,49 @@
+import numpy as np
+import pytest
+import pyrecest.backend
+
+from pyrecest.backend import array
+from pyrecest.utils.point_set_registration import (
+    estimate_transform,
+    joint_registration_assignment,
+)
+
+pytestmark = pytest.mark.skipif(
+    pyrecest.backend.__backend_name__ == "jax",  # pylint: disable=no-member
+    reason="Point-set registration is not supported on JAX.",
+)
+
+_SOURCE = array([[0.0, 0.0], [1.0, 0.0], [0.0, 1.0]])
+_REFLECTED = array([[0.0, 0.0], [-1.0, 0.0], [0.0, 1.0]])
+
+
+@pytest.mark.parametrize("invalid_flag", ["False", "True", 0, 1, None])
+def test_estimate_transform_rejects_non_boolean_allow_reflection(invalid_flag):
+    with pytest.raises(TypeError, match="allow_reflection must be a boolean"):
+        estimate_transform(
+            _SOURCE,
+            _REFLECTED,
+            model="rigid",
+            allow_reflection=invalid_flag,
+        )
+
+
+def test_joint_registration_rejects_truthy_string_allow_reflection():
+    with pytest.raises(TypeError, match="allow_reflection must be a boolean"):
+        joint_registration_assignment(
+            _SOURCE,
+            _REFLECTED,
+            model="rigid",
+            allow_reflection="False",
+        )
+
+
+def test_numpy_boolean_allow_reflection_is_accepted():
+    transform = estimate_transform(
+        _SOURCE,
+        _REFLECTED,
+        model="rigid",
+        allow_reflection=np.bool_(True),
+    )
+
+    assert float(np.linalg.det(np.asarray(transform.matrix))) < 0.0