Preserve circular Fourier subclasses in conversion factories

src/pyrecest/distributions/circle/circular_fourier_distribution.py

@@ -357,8 +357,9 @@ def get_full_c(self):
         full_c = concatenate([neg_c, self.c])  # Concatenate arrays to get full spectrum
         return full_c
 
-    @staticmethod
+    @classmethod
     def from_distribution(
+        cls,
         distribution: AbstractCircularDistribution,
         n: Union[int, int32, int64],
         transformation: str = "sqrt",
@@ -379,7 +380,7 @@ def from_distribution(
                     for k in range(int(n) // 2 + 1)
                 ]
             )
-            fd = CircularFourierDistribution(
+            fd = cls(
                 c=coeffs,
                 n=int(n),
                 transformation=transformation,
@@ -398,14 +399,15 @@ def from_distribution(
                 fvals = sqrt(fvals)
             else:
                 raise NotImplementedError("Transformation not supported.")
-            fd = CircularFourierDistribution.from_function_values(
+            fd = cls.from_function_values(
                 fvals, transformation, store_values_multiplied_by_n
             )
 
         return fd
 
-    @staticmethod
+    @classmethod
     def from_function_values(
+        cls,
         fvals,
         transformation: str = "sqrt",
         store_values_multiplied_by_n: bool = True,
@@ -416,7 +418,7 @@ def from_function_values(
         if not store_values_multiplied_by_n:
             c = c * (1.0 / n_values)
 
-        fd = CircularFourierDistribution(
+        fd = cls(
             c=c,
             transformation=transformation,
             n=n_values,

tests/distributions/test_circular_fourier_factory_subclass_preservation.py

@@ -0,0 +1,59 @@
+import unittest
+
+# pylint: disable=no-name-in-module,no-member
+from pyrecest.backend import array
+from pyrecest.distributions.circle.circular_dirac_distribution import (
+    CircularDiracDistribution,
+)
+from pyrecest.distributions.circle.circular_fourier_distribution import (
+    CircularFourierDistribution,
+)
+from pyrecest.distributions.circle.von_mises_distribution import VonMisesDistribution
+from pyrecest.distributions.conversion import convert_distribution
+
+
+class _CircularFourierSubclass(CircularFourierDistribution):
+    pass
+
+
+class CircularFourierFactorySubclassPreservationTest(unittest.TestCase):
+    def test_conversion_factory_preserves_requested_subclass_for_density_source(self):
+        source = VonMisesDistribution(0.3, 2.0)
+
+        converted = convert_distribution(
+            source,
+            _CircularFourierSubclass,
+            n=9,
+            transformation="identity",
+            store_values_multiplied_by_n=False,
+        )
+
+        self.assertIsInstance(converted, _CircularFourierSubclass)
+
+    def test_conversion_factory_preserves_requested_subclass_for_dirac_source(self):
+        source = CircularDiracDistribution(array([0.0, 1.0]))
+
+        converted = convert_distribution(
+            source,
+            _CircularFourierSubclass,
+            n=9,
+            transformation="identity",
+            store_values_multiplied_by_n=False,
+        )
+
+        self.assertIsInstance(converted, _CircularFourierSubclass)
+
+    def test_function_value_factory_preserves_requested_subclass(self):
+        function_values = array([1.0, 0.9, 0.8, 0.7, 0.6, 0.7, 0.8, 0.9, 1.0])
+
+        converted = _CircularFourierSubclass.from_function_values(
+            function_values,
+            transformation="identity",
+            store_values_multiplied_by_n=False,
+        )
+
+        self.assertIsInstance(converted, _CircularFourierSubclass)
+
+
+if __name__ == "__main__":
+    unittest.main()