topython converts floats and honors maxdigits uses default rounding of roundhalfeven should be able to filter decimal fields using strings 8023 ensure decimals don t go through a corrupting float conversion during save 5079 really big values can be used in a filter statement this should not crash trailing zeros in the fractional part aren t truncated obj foo objects createabar ddecimal8 320 obj refreshfromdb self assertequalobj d comparetotaldecimal8 320 decimal0 to_python converts floats and honors max_digits uses default rounding of round_half_even should be able to filter decimal fields using strings 8023 ensure decimals don t go through a corrupting float conversion during save 5079 really big values can be used in a filter statement this should not crash trailing zeros in the fractional part aren t truncated
import math
from decimal import Decimal

from django.core import validators
from django.core.exceptions import ValidationError
from django.db import models
from django.test import TestCase

from .models import BigD, Foo


class DecimalFieldTests(TestCase):
    def test_to_python(self):
        f = models.DecimalField(max_digits=4, decimal_places=2)
        self.assertEqual(f.to_python(3), Decimal("3"))
        self.assertEqual(f.to_python("3.14"), Decimal("3.14"))
        
        self.assertEqual(f.to_python(3.1415926535897), Decimal("3.142"))
        self.assertEqual(f.to_python(2.4), Decimal("2.400"))
        
        self.assertEqual(f.to_python(2.0625), Decimal("2.062"))
        self.assertEqual(f.to_python(2.1875), Decimal("2.188"))

    def test_invalid_value(self):
        field = models.DecimalField(max_digits=4, decimal_places=2)
        msg = "“%s” value must be a decimal number."
        tests = [
            (),
            [],
            {},
            set(),
            object(),
            complex(),
            "non-numeric string",
            b"non-numeric byte-string",
        ]
        for value in tests:
            with self.subTest(value):
                with self.assertRaisesMessage(ValidationError, msg % (value,)):
                    field.clean(value, None)

    def test_default(self):
        f = models.DecimalField(default=Decimal("0.00"))
        self.assertEqual(f.get_default(), Decimal("0.00"))

    def test_get_prep_value(self):
        f = models.DecimalField(max_digits=5, decimal_places=1)
        self.assertIsNone(f.get_prep_value(None))
        self.assertEqual(f.get_prep_value("2.4"), Decimal("2.4"))

    def test_filter_with_strings(self):
        
        foo = Foo.objects.create(a="abc", d=Decimal("12.34"))
        self.assertEqual(list(Foo.objects.filter(d="12.34")), [foo])

    def test_save_without_float_conversion(self):
        
        bd = BigD(d="12.9")
        bd.save()
        bd = BigD.objects.get(pk=bd.pk)
        self.assertEqual(bd.d, Decimal("12.9"))

    def test_save_nan_invalid(self):
        msg = "“nan” value must be a decimal number."
        for value in [float("nan"), math.nan, "nan"]:
            with self.subTest(value), self.assertRaisesMessage(ValidationError, msg):
                BigD.objects.create(d=value)

    def test_save_inf_invalid(self):
        msg = "“inf” value must be a decimal number."
        for value in [float("inf"), math.inf, "inf"]:
            with self.subTest(value), self.assertRaisesMessage(ValidationError, msg):
                BigD.objects.create(d=value)
        msg = "“-inf” value must be a decimal number."
        for value in [float("-inf"), -math.inf, "-inf"]:
            with self.subTest(value), self.assertRaisesMessage(ValidationError, msg):
                BigD.objects.create(d=value)

    def test_fetch_from_db_without_float_rounding(self):
        big_decimal = BigD.objects.create(d=Decimal(".100000000000000000000000000005"))
        big_decimal.refresh_from_db()
        self.assertEqual(big_decimal.d, Decimal(".100000000000000000000000000005"))

    def test_lookup_really_big_value(self):
        
        
        self.assertSequenceEqual(Foo.objects.filter(d__gte=100000000000), [])

    def test_lookup_decimal_larger_than_max_digits(self):
        self.assertSequenceEqual(Foo.objects.filter(d__lte=Decimal("123456")), [])

    def test_max_digits_validation(self):
        field = models.DecimalField(max_digits=2)
        expected_message = validators.DecimalValidator.messages["max_digits"] % {
            "max": 2
        }
        with self.assertRaisesMessage(ValidationError, expected_message):
            field.clean(100, None)

    def test_max_decimal_places_validation(self):
        field = models.DecimalField(decimal_places=1)
        expected_message = validators.DecimalValidator.messages[
            "max_decimal_places"
        ] % {"max": 1}
        with self.assertRaisesMessage(ValidationError, expected_message):
            field.clean(Decimal("0.99"), None)

    def test_max_whole_digits_validation(self):
        field = models.DecimalField(max_digits=3, decimal_places=1)
        expected_message = validators.DecimalValidator.messages["max_whole_digits"] % {
            "max": 2
        }
        with self.assertRaisesMessage(ValidationError, expected_message):
            field.clean(Decimal("999"), None)

    def test_roundtrip_with_trailing_zeros(self):
        
        obj = Foo.objects.create(a="bar", d=Decimal("8.320"))
        obj.refresh_from_db()
        self.assertEqual(obj.d.compare_total(Decimal("8.320")), Decimal("0"))