refreshfromdb cannot be used because that needs the pk to already be known to django refreshfromdb cannot be used because that needs the pk to already be known to django refresh_from_db cannot be used because that needs the pk to already be known to django refresh_from_db cannot be used because that needs the pk to already be known to django combined expression combined expression
from datetime import datetime
from decimal import Decimal
from math import pi

from django.db import connection
from django.db.models import Case, F, FloatField, Value, When
from django.db.models.expressions import (
    Expression,
    ExpressionList,
    ExpressionWrapper,
    Func,
    OrderByList,
    RawSQL,
)
from django.db.models.functions import Collate
from django.db.models.lookups import GreaterThan
from django.test import SimpleTestCase, TestCase, skipIfDBFeature, skipUnlessDBFeature

from .models import (
    Article,
    DBArticle,
    DBDefaults,
    DBDefaultsFK,
    DBDefaultsFunction,
    DBDefaultsPK,
)


class DefaultTests(TestCase):
    def test_field_defaults(self):
        a = Article()
        now = datetime.now()
        a.save()

        self.assertIsInstance(a.id, int)
        self.assertEqual(a.headline, "Default headline")
        self.assertLess((now - a.pub_date).seconds, 5)

    @skipUnlessDBFeature(
        "can_return_columns_from_insert", "supports_expression_defaults"
    )
    def test_field_db_defaults_returning(self):
        a = DBArticle()
        a.save()
        self.assertIsInstance(a.id, int)
        self.assertEqual(a.headline, "Default headline")
        self.assertIsInstance(a.pub_date, datetime)
        self.assertEqual(a.cost, Decimal("3.33"))

    @skipIfDBFeature("can_return_columns_from_insert")
    @skipUnlessDBFeature("supports_expression_defaults")
    def test_field_db_defaults_refresh(self):
        a = DBArticle()
        a.save()
        a.refresh_from_db()
        self.assertIsInstance(a.id, int)
        self.assertEqual(a.headline, "Default headline")
        self.assertIsInstance(a.pub_date, datetime)
        self.assertEqual(a.cost, Decimal("3.33"))

    def test_null_db_default(self):
        obj1 = DBDefaults.objects.create()
        if not connection.features.can_return_columns_from_insert:
            obj1.refresh_from_db()
        self.assertEqual(obj1.null, 1.1)

        obj2 = DBDefaults.objects.create(null=None)
        self.assertIsNone(obj2.null)

    @skipUnlessDBFeature("supports_expression_defaults")
    def test_db_default_function(self):
        m = DBDefaultsFunction.objects.create()
        if not connection.features.can_return_columns_from_insert:
            m.refresh_from_db()
        self.assertAlmostEqual(m.number, pi)
        self.assertEqual(m.year, datetime.now().year)
        self.assertAlmostEqual(m.added, pi + 4.5)
        self.assertEqual(m.multiple_subfunctions, 4.5)

    @skipUnlessDBFeature("insert_test_table_with_defaults")
    def test_both_default(self):
        create_sql = connection.features.insert_test_table_with_defaults
        with connection.cursor() as cursor:
            cursor.execute(create_sql.format(DBDefaults._meta.db_table))
        obj1 = DBDefaults.objects.get()
        self.assertEqual(obj1.both, 2)

        obj2 = DBDefaults.objects.create()
        self.assertEqual(obj2.both, 1)

    def test_pk_db_default(self):
        obj1 = DBDefaultsPK.objects.create()
        if not connection.features.can_return_columns_from_insert:
            
            
            obj1 = DBDefaultsPK.objects.get(pk="en")
        self.assertEqual(obj1.pk, "en")
        self.assertEqual(obj1.language_code, "en")

        obj2 = DBDefaultsPK.objects.create(language_code="de")
        self.assertEqual(obj2.pk, "de")
        self.assertEqual(obj2.language_code, "de")

    def test_foreign_key_db_default(self):
        parent1 = DBDefaultsPK.objects.create(language_code="fr")
        child1 = DBDefaultsFK.objects.create()
        if not connection.features.can_return_columns_from_insert:
            child1.refresh_from_db()
        self.assertEqual(child1.language_code, parent1)

        parent2 = DBDefaultsPK.objects.create()
        if not connection.features.can_return_columns_from_insert:
            
            
            parent2 = DBDefaultsPK.objects.get(pk="en")
        child2 = DBDefaultsFK.objects.create(language_code=parent2)
        self.assertEqual(child2.language_code, parent2)

    @skipUnlessDBFeature(
        "can_return_columns_from_insert", "supports_expression_defaults"
    )
    def test_case_when_db_default_returning(self):
        m = DBDefaultsFunction.objects.create()
        self.assertEqual(m.case_when, 3)

    @skipIfDBFeature("can_return_columns_from_insert")
    @skipUnlessDBFeature("supports_expression_defaults")
    def test_case_when_db_default_no_returning(self):
        m = DBDefaultsFunction.objects.create()
        m.refresh_from_db()
        self.assertEqual(m.case_when, 3)

    @skipUnlessDBFeature("supports_expression_defaults")
    def test_bulk_create_all_db_defaults(self):
        articles = [DBArticle(), DBArticle()]
        DBArticle.objects.bulk_create(articles)

        headlines = DBArticle.objects.values_list("headline", flat=True)
        self.assertSequenceEqual(headlines, ["Default headline", "Default headline"])

    @skipUnlessDBFeature("supports_expression_defaults")
    def test_bulk_create_all_db_defaults_one_field(self):
        pub_date = datetime.now()
        articles = [DBArticle(pub_date=pub_date), DBArticle(pub_date=pub_date)]
        DBArticle.objects.bulk_create(articles)

        headlines = DBArticle.objects.values_list("headline", "pub_date", "cost")
        self.assertSequenceEqual(
            headlines,
            [
                ("Default headline", pub_date, Decimal("3.33")),
                ("Default headline", pub_date, Decimal("3.33")),
            ],
        )

    @skipUnlessDBFeature("supports_expression_defaults")
    def test_bulk_create_mixed_db_defaults(self):
        articles = [DBArticle(), DBArticle(headline="Something else")]
        DBArticle.objects.bulk_create(articles)

        headlines = DBArticle.objects.values_list("headline", flat=True)
        self.assertCountEqual(headlines, ["Default headline", "Something else"])

    @skipUnlessDBFeature("supports_expression_defaults")
    def test_bulk_create_mixed_db_defaults_function(self):
        instances = [DBDefaultsFunction(), DBDefaultsFunction(year=2000)]
        DBDefaultsFunction.objects.bulk_create(instances)

        years = DBDefaultsFunction.objects.values_list("year", flat=True)
        self.assertCountEqual(years, [2000, datetime.now().year])


class AllowedDefaultTests(SimpleTestCase):
    def test_allowed(self):
        class Max(Func):
            function = "MAX"

        tests = [
            Value(10),
            Max(1, 2),
            RawSQL("Now()", ()),
            Value(10) + Value(7),  
            ExpressionList(Value(1), Value(2)),
            ExpressionWrapper(Value(1), output_field=FloatField()),
            Case(When(GreaterThan(2, 1), then=3), default=4),
        ]
        for expression in tests:
            with self.subTest(expression=expression):
                self.assertIs(expression.allowed_default, True)

    def test_disallowed(self):
        class Max(Func):
            function = "MAX"

        tests = [
            Expression(),
            F("field"),
            Max(F("count"), 1),
            Value(10) + F("count"),  
            ExpressionList(F("count"), Value(2)),
            ExpressionWrapper(F("count"), output_field=FloatField()),
            Collate(Value("John"), "nocase"),
            OrderByList("field"),
        ]
        for expression in tests:
            with self.subTest(expression=expression):
                self.assertIs(expression.allowed_default, False)