Reject non-boolean circular Fourier scaling flags

src/pyrecest/distributions/circle/circular_fourier_distribution.py

@@ -3,6 +3,7 @@
 from typing import Union
 
 import matplotlib.pyplot as plt
+import numpy as np
 
 # pylint: disable=redefined-builtin,no-name-in-module,no-member
 # pylint: disable=no-name-in-module,no-member
@@ -52,6 +53,21 @@ def _ensure_odd_n(n) -> None:
     _validate_odd_n(n)
 
 
+def _validate_scaling_flag(value, name: str) -> bool:
+    """Return a real boolean scaling flag without accepting truthy values."""
+    if np.ma.is_masked(value):
+        raise TypeError(f"{name} must be a boolean.")
+    if isinstance(value, (bool, np.bool_)):
+        return bool(value)
+    try:
+        value_array = np.asarray(value)
+    except (TypeError, ValueError, RuntimeError, OverflowError) as exc:
+        raise TypeError(f"{name} must be a boolean.") from exc
+    if value_array.shape == () and value_array.dtype == np.bool_:
+        return bool(value_array.item())
+    raise TypeError(f"{name} must be a boolean.")
+
+
 class CircularFourierDistribution(AbstractCircularDistribution):
     """Circular distribution represented by a Fourier series.
 
@@ -120,7 +136,9 @@ def __init__(
         else:
             raise ValueError("Need to provide either c or a and b.")
 
-        self.multiplied_by_n = multiplied_by_n
+        self.multiplied_by_n = _validate_scaling_flag(
+            multiplied_by_n, "multiplied_by_n"
+        )
         self.transformation = transformation
 
     def __sub__(
@@ -365,6 +383,9 @@ def from_distribution(
         transformation: str = "sqrt",
         store_values_multiplied_by_n: bool = True,
     ) -> "CircularFourierDistribution":
+        store_values_multiplied_by_n = _validate_scaling_flag(
+            store_values_multiplied_by_n, "store_values_multiplied_by_n"
+        )
         n = _validate_odd_n(n)
         if isinstance(distribution, CircularDiracDistribution):
             if transformation != "identity":
@@ -412,6 +433,9 @@ def from_function_values(
         transformation: str = "sqrt",
         store_values_multiplied_by_n: bool = True,
     ) -> "CircularFourierDistribution":
+        store_values_multiplied_by_n = _validate_scaling_flag(
+            store_values_multiplied_by_n, "store_values_multiplied_by_n"
+        )
         n_values = fvals.shape[0]
         _ensure_odd_n(n_values)
         c = fft.rfft(fvals)

tests/distributions/test_circular_fourier_bool_validation.py

@@ -0,0 +1,59 @@
+import numpy as np
+import pytest
+
+from pyrecest.backend import array
+from pyrecest.distributions import CircularFourierDistribution, VonMisesDistribution
+
+
+@pytest.mark.parametrize("invalid_flag", ["False", "True", 0, 1, None])
+def test_constructor_rejects_non_boolean_multiplied_by_n(invalid_flag):
+    with pytest.raises(TypeError, match="multiplied_by_n must be a boolean"):
+        CircularFourierDistribution(
+            c=array([1.0]),
+            n=1,
+            transformation="identity",
+            multiplied_by_n=invalid_flag,
+        )
+
+
+@pytest.mark.parametrize("invalid_flag", ["False", "True", 0, 1, None])
+def test_function_value_factory_rejects_non_boolean_scaling_flag(invalid_flag):
+    with pytest.raises(
+        TypeError, match="store_values_multiplied_by_n must be a boolean"
+    ):
+        CircularFourierDistribution.from_function_values(
+            array([1.0, 1.0, 1.0]),
+            transformation="identity",
+            store_values_multiplied_by_n=invalid_flag,
+        )
+
+
+def test_distribution_factory_rejects_truthy_string_scaling_flag():
+    distribution = VonMisesDistribution(array(0.0), array(1.0))
+
+    with pytest.raises(
+        TypeError, match="store_values_multiplied_by_n must be a boolean"
+    ):
+        CircularFourierDistribution.from_distribution(
+            distribution,
+            n=3,
+            transformation="identity",
+            store_values_multiplied_by_n="False",
+        )
+
+
+def test_numpy_boolean_scaling_flags_are_accepted():
+    direct = CircularFourierDistribution(
+        c=array([1.0]),
+        n=1,
+        transformation="identity",
+        multiplied_by_n=np.bool_(False),
+    )
+    from_values = CircularFourierDistribution.from_function_values(
+        array([1.0, 1.0, 1.0]),
+        transformation="identity",
+        store_values_multiplied_by_n=np.bool_(False),
+    )
+
+    assert direct.multiplied_by_n is False
+    assert from_values.multiplied_by_n is False