Merge pull request #91 from SSJenny90/fix_temperature_conversion_errors

Fix OffsetUnitCalculus error for quantity fields that define temperature values

AUTHORS.rst

@@ -9,3 +9,4 @@ Contributors
 * Alex Bhandari <[email protected]>
 * Jonas Haag <[email protected]>
 * Igor Kozyrenko <[email protected]>
+* Samuel Scott Jennings <[email protected]>

src/quantityfield/fields.py

@@ -170,7 +170,7 @@ def value_to_string(self, obj) -> str:
     def from_db_value(self, value: Any, *args, **kwargs) -> Optional[Quantity]:
         if value is None:
             return None
-        return self.ureg.Quantity(value * getattr(self.ureg, self.base_units))
+        return self.ureg.Quantity(value, getattr(self.ureg, self.base_units))
 
     def to_python(self, value) -> Optional[Quantity]:
         if isinstance(value, Quantity):
@@ -187,7 +187,7 @@ def to_python(self, value) -> Optional[Quantity]:
 
         value = cast(NUMBER_TYPE, to_number(value))
 
-        return self.ureg.Quantity(value * getattr(self.ureg, self.base_units))
+        return self.ureg.Quantity(value, getattr(self.ureg, self.base_units))
 
     def clean(self, value, model_instance) -> Quantity:
         """
@@ -331,7 +331,7 @@ def clean(self, value):
         except (ValueError, TypeError):
             raise ValidationError(self.error_messages["invalid"], code="invalid")
 
-        val = self.ureg.Quantity(val * getattr(self.ureg, units)).to(self.base_units)
+        val = self.ureg.Quantity(val, getattr(self.ureg, units)).to(self.base_units)
         self.validate(val.magnitude)
         self.run_validators(val.magnitude)
         return val

tests/dummyapp/admin.py

@@ -23,3 +23,4 @@ def get_readonly_fields(self, request, obj=None):
 admin.site.register(FloatFieldSaveModel, ReadOnlyEditing)
 admin.site.register(HayBale, ReadOnlyEditing)
 admin.site.register(IntFieldSaveModel, ReadOnlyEditing)
+admin.site.register(OffsetUnitFloatFieldSaveModel, ReadOnlyEditing)

tests/dummyapp/migrations/0002_offsetunitfloatfieldsavemodel.py

@@ -0,0 +1,38 @@
+# Generated by Django 4.2.5 on 2023-09-25 08:24
+
+from django.db import migrations, models
+
+import quantityfield.fields
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("dummyapp", "0001_initial"),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name="OffsetUnitFloatFieldSaveModel",
+            fields=[
+                (
+                    "id",
+                    models.BigAutoField(
+                        auto_created=True,
+                        primary_key=True,
+                        serialize=False,
+                        verbose_name="ID",
+                    ),
+                ),
+                ("name", models.CharField(max_length=20)),
+                (
+                    "weight",
+                    quantityfield.fields.QuantityField(
+                        base_units="degC", unit_choices=["degC"]
+                    ),
+                ),
+            ],
+            options={
+                "abstract": False,
+            },
+        ),
+    ]

tests/dummyapp/models.py

@@ -85,3 +85,9 @@ class ChoicesDefinedInModel(models.Model):
 
 class ChoicesDefinedInModelInt(models.Model):
     weight = IntegerQuantityField("kilogram", unit_choices=["milligram", "pounds"])
+
+
+class OffsetUnitFloatFieldSaveModel(FieldSaveModel):
+    # Note: This is a temperature not a weight.
+    #       We wanted to reuse existing test cases inheritance
+    weight = QuantityField("degC")

tests/test_field.py

@@ -35,6 +35,7 @@
     FieldSaveModel,
     FloatFieldSaveModel,
     IntFieldSaveModel,
+    OffsetUnitFloatFieldSaveModel,
 )
 
 Quantity = ureg.Quantity
@@ -475,3 +476,41 @@ class TestIntFieldSave(IntLikeFieldSaveTestBase, TestCase):
 
 class TestBigIntFieldSave(IntLikeFieldSaveTestBase, TestCase):
     MODEL = BigIntFieldSaveModel
+
+
+class TestOffsetUnitFieldSaveTestBase(FloatLikeFieldSaveTestBase, TestCase):
+    MODEL = OffsetUnitFloatFieldSaveModel
+    DEFAULT_WEIGHT_QUANTITY_STR = "100.0 degree_Celsius"
+    HEAVIEST = 1000
+    LIGHTEST = 1
+    FAHRENHEIT_VALUE = 212  # 100 celsius = 212 fahrenheit
+    COMPARE_QUANTITY = Quantity(100, ureg.fahrenheit)
+
+    # Note: weight here is a temperature,
+    #       reused the field name to allow inheritance of float test cae
+
+    def test_value_conversion(self):
+        obj = self.MODEL.objects.first()
+        degF = obj.weight.to(ureg.fahrenheit)  # weight is in celsius
+        self.assertAlmostEqual(degF.magnitude, self.FAHRENHEIT_VALUE)
+        self.assertEqual(degF.units, ureg.fahrenheit)
+
+    def test_value_stored_as_quantity(self):
+        obj = self.MODEL.objects.first()
+        self.assertIsInstance(obj.weight, Quantity)
+        self.assertEqual(str(obj.weight), self.DEFAULT_WEIGHT_QUANTITY_STR)
+
+    def test_stores_value_in_base_units(self):
+        self.MODEL.objects.create(weight=self.FAHRENHEIT_VALUE, name="fahrenheit")
+        item = self.MODEL.objects.get(name="fahrenheit")
+        self.assertEqual(item.weight.units, "degree_Celsius")
+        self.assertAlmostEqual(item.weight.magnitude, self.FAHRENHEIT_VALUE)
+
+    def test_comparison_with_quantity(self):
+        weight = Quantity(20, ureg.celsius)
+        qs = self.MODEL.objects.filter(weight__gt=weight)
+        self.assertNotIn(self.lightest, qs)
+
+    def test_comparison_with_quantity_respects_units(self):
+        qs = self.MODEL.objects.filter(weight__gt=self.COMPARE_QUANTITY)
+        self.assertNotIn(self.lightest, qs)

tox.ini

@@ -57,4 +57,4 @@ docker=
     postgres
 
 commands =
-    pytest -x {posargs}
+    pytest -vv {posargs}