Refs #28643 -- Added math database functions.

Thanks Nick Pope for much review.

tests/db_functions/math/test_degrees.py

@@ -0,0 +1,51 @@
+import math
+from decimal import Decimal
+
+from django.db.models import DecimalField
+from django.db.models.functions import Degrees
+from django.test import TestCase
+
+from ..models import DecimalModel, FloatModel, IntegerModel
+
+
+class DegreesTests(TestCase):
+
+    def test_decimal(self):
+        DecimalModel.objects.create(n1=Decimal('-12.9'), n2=Decimal('0.6'))
+        obj = DecimalModel.objects.annotate(n1_degrees=Degrees('n1'), n2_degrees=Degrees('n2')).first()
+        self.assertIsInstance(obj.n1_degrees, Decimal)
+        self.assertIsInstance(obj.n2_degrees, Decimal)
+        self.assertAlmostEqual(obj.n1_degrees, Decimal(math.degrees(obj.n1)))
+        self.assertAlmostEqual(obj.n2_degrees, Decimal(math.degrees(obj.n2)))
+
+    def test_float(self):
+        FloatModel.objects.create(f1=-27.5, f2=0.33)
+        obj = FloatModel.objects.annotate(f1_degrees=Degrees('f1'), f2_degrees=Degrees('f2')).first()
+        self.assertIsInstance(obj.f1_degrees, float)
+        self.assertIsInstance(obj.f2_degrees, float)
+        self.assertAlmostEqual(obj.f1_degrees, math.degrees(obj.f1))
+        self.assertAlmostEqual(obj.f2_degrees, math.degrees(obj.f2))
+
+    def test_integer(self):
+        IntegerModel.objects.create(small=-20, normal=15, big=-1)
+        obj = IntegerModel.objects.annotate(
+            small_degrees=Degrees('small'),
+            normal_degrees=Degrees('normal'),
+            big_degrees=Degrees('big'),
+        ).first()
+        self.assertIsInstance(obj.small_degrees, float)
+        self.assertIsInstance(obj.normal_degrees, float)
+        self.assertIsInstance(obj.big_degrees, float)
+        self.assertAlmostEqual(obj.small_degrees, math.degrees(obj.small))
+        self.assertAlmostEqual(obj.normal_degrees, math.degrees(obj.normal))
+        self.assertAlmostEqual(obj.big_degrees, math.degrees(obj.big))
+
+    def test_transform(self):
+        try:
+            DecimalField.register_lookup(Degrees)
+            DecimalModel.objects.create(n1=Decimal('5.4'), n2=Decimal('0'))
+            DecimalModel.objects.create(n1=Decimal('-30'), n2=Decimal('0'))
+            objs = DecimalModel.objects.filter(n1__degrees__gt=0)
+            self.assertQuerysetEqual(objs, [Decimal('5.4')], lambda a: a.n1)
+        finally:
+            DecimalField._unregister_lookup(Degrees)