Fixed #30271 -- Added the Sign database function.

tests/db_functions/math/test_sign.py

@@ -0,0 +1,53 @@
+from decimal import Decimal
+
+from django.db.models import DecimalField
+from django.db.models.functions import Sign
+from django.test import TestCase
+from django.test.utils import register_lookup
+
+from ..models import DecimalModel, FloatModel, IntegerModel
+
+
+class SignTests(TestCase):
+
+    def test_null(self):
+        IntegerModel.objects.create()
+        obj = IntegerModel.objects.annotate(null_sign=Sign('normal')).first()
+        self.assertIsNone(obj.null_sign)
+
+    def test_decimal(self):
+        DecimalModel.objects.create(n1=Decimal('-12.9'), n2=Decimal('0.6'))
+        obj = DecimalModel.objects.annotate(n1_sign=Sign('n1'), n2_sign=Sign('n2')).first()
+        self.assertIsInstance(obj.n1_sign, Decimal)
+        self.assertIsInstance(obj.n2_sign, Decimal)
+        self.assertEqual(obj.n1_sign, Decimal('-1'))
+        self.assertEqual(obj.n2_sign, Decimal('1'))
+
+    def test_float(self):
+        FloatModel.objects.create(f1=-27.5, f2=0.33)
+        obj = FloatModel.objects.annotate(f1_sign=Sign('f1'), f2_sign=Sign('f2')).first()
+        self.assertIsInstance(obj.f1_sign, float)
+        self.assertIsInstance(obj.f2_sign, float)
+        self.assertEqual(obj.f1_sign, -1.0)
+        self.assertEqual(obj.f2_sign, 1.0)
+
+    def test_integer(self):
+        IntegerModel.objects.create(small=-20, normal=0, big=20)
+        obj = IntegerModel.objects.annotate(
+            small_sign=Sign('small'),
+            normal_sign=Sign('normal'),
+            big_sign=Sign('big'),
+        ).first()
+        self.assertIsInstance(obj.small_sign, int)
+        self.assertIsInstance(obj.normal_sign, int)
+        self.assertIsInstance(obj.big_sign, int)
+        self.assertEqual(obj.small_sign, -1)
+        self.assertEqual(obj.normal_sign, 0)
+        self.assertEqual(obj.big_sign, 1)
+
+    def test_transform(self):
+        with register_lookup(DecimalField, Sign):
+            DecimalModel.objects.create(n1=Decimal('5.4'), n2=Decimal('0'))
+            DecimalModel.objects.create(n1=Decimal('-0.1'), n2=Decimal('0'))
+            obj = DecimalModel.objects.filter(n1__sign__lt=0, n2__sign=0).get()
+            self.assertEqual(obj.n1, Decimal('-0.1'))