django/tests/get_earliest_or_latest/tests.py

from datetime import datetime

from django.db.models import Avg
from django.test import TestCase

from .models import Article, Comment, IndexErrorArticle, Person


class EarliestOrLatestTests(TestCase):
    """Tests for the earliest() and latest() objects methods"""

    @classmethod
    def setUpClass(cls):
        super().setUpClass()
        cls._article_get_latest_by = Article._meta.get_latest_by

    def tearDown(self):
        Article._meta.get_latest_by = self._article_get_latest_by

    def test_earliest(self):
        # Because no Articles exist yet, earliest() raises ArticleDoesNotExist.
        with self.assertRaises(Article.DoesNotExist):
            Article.objects.earliest()

        a1 = Article.objects.create(
            headline="Article 1",
            pub_date=datetime(2005, 7, 26),
            expire_date=datetime(2005, 9, 1),
        )
        a2 = Article.objects.create(
            headline="Article 2",
            pub_date=datetime(2005, 7, 27),
            expire_date=datetime(2005, 7, 28),
        )
        a3 = Article.objects.create(
            headline="Article 3",
            pub_date=datetime(2005, 7, 28),
            expire_date=datetime(2005, 8, 27),
        )
        a4 = Article.objects.create(
            headline="Article 4",
            pub_date=datetime(2005, 7, 28),
            expire_date=datetime(2005, 7, 30),
        )

        # Get the earliest Article.
        self.assertEqual(Article.objects.earliest(), a1)
        # Get the earliest Article that matches certain filters.
        self.assertEqual(
            Article.objects.filter(pub_date__gt=datetime(2005, 7, 26)).earliest(), a2
        )

        # Pass a custom field name to earliest() to change the field that's used
        # to determine the earliest object.
        self.assertEqual(Article.objects.earliest("expire_date"), a2)
        self.assertEqual(
            Article.objects.filter(pub_date__gt=datetime(2005, 7, 26)).earliest(
                "expire_date"
            ),
            a2,
        )

        # earliest() overrides any other ordering specified on the query.
        # Refs #11283.
        self.assertEqual(Article.objects.order_by("id").earliest(), a1)

        # Error is raised if the user forgot to add a get_latest_by
        # in the Model.Meta
        Article.objects.model._meta.get_latest_by = None
        with self.assertRaisesMessage(
            ValueError,
            "earliest() and latest() require either fields as positional "
            "arguments or 'get_latest_by' in the model's Meta.",
        ):
            Article.objects.earliest()

        # Earliest publication date, earliest expire date.
        self.assertEqual(
            Article.objects.filter(pub_date=datetime(2005, 7, 28)).earliest(
                "pub_date", "expire_date"
            ),
            a4,
        )
        # Earliest publication date, latest expire date.
        self.assertEqual(
            Article.objects.filter(pub_date=datetime(2005, 7, 28)).earliest(
                "pub_date", "-expire_date"
            ),
            a3,
        )

        # Meta.get_latest_by may be a tuple.
        Article.objects.model._meta.get_latest_by = ("pub_date", "expire_date")
        self.assertEqual(
            Article.objects.filter(pub_date=datetime(2005, 7, 28)).earliest(), a4
        )

    def test_earliest_sliced_queryset(self):
        msg = "Cannot change a query once a slice has been taken."
        with self.assertRaisesMessage(TypeError, msg):
            Article.objects.all()[0:5].earliest()

    def test_latest(self):
        # Because no Articles exist yet, latest() raises ArticleDoesNotExist.
        with self.assertRaises(Article.DoesNotExist):
            Article.objects.latest()

        a1 = Article.objects.create(
            headline="Article 1",
            pub_date=datetime(2005, 7, 26),
            expire_date=datetime(2005, 9, 1),
        )
        a2 = Article.objects.create(
            headline="Article 2",
            pub_date=datetime(2005, 7, 27),
            expire_date=datetime(2005, 7, 28),
        )
        a3 = Article.objects.create(
            headline="Article 3",
            pub_date=datetime(2005, 7, 27),
            expire_date=datetime(2005, 8, 27),
        )
        a4 = Article.objects.create(
            headline="Article 4",
            pub_date=datetime(2005, 7, 28),
            expire_date=datetime(2005, 7, 30),
        )

        # Get the latest Article.
        self.assertEqual(Article.objects.latest(), a4)
        # Get the latest Article that matches certain filters.
        self.assertEqual(
            Article.objects.filter(pub_date__lt=datetime(2005, 7, 27)).latest(), a1
        )

        # Pass a custom field name to latest() to change the field that's used
        # to determine the latest object.
        self.assertEqual(Article.objects.latest("expire_date"), a1)
        self.assertEqual(
            Article.objects.filter(pub_date__gt=datetime(2005, 7, 26)).latest(
                "expire_date"
            ),
            a3,
        )

        # latest() overrides any other ordering specified on the query (#11283).
        self.assertEqual(Article.objects.order_by("id").latest(), a4)

        # Error is raised if get_latest_by isn't in Model.Meta.
        Article.objects.model._meta.get_latest_by = None
        with self.assertRaisesMessage(
            ValueError,
            "earliest() and latest() require either fields as positional "
            "arguments or 'get_latest_by' in the model's Meta.",
        ):
            Article.objects.latest()

        # Latest publication date, latest expire date.
        self.assertEqual(
            Article.objects.filter(pub_date=datetime(2005, 7, 27)).latest(
                "pub_date", "expire_date"
            ),
            a3,
        )
        # Latest publication date, earliest expire date.
        self.assertEqual(
            Article.objects.filter(pub_date=datetime(2005, 7, 27)).latest(
                "pub_date", "-expire_date"
            ),
            a2,
        )

        # Meta.get_latest_by may be a tuple.
        Article.objects.model._meta.get_latest_by = ("pub_date", "expire_date")
        self.assertEqual(
            Article.objects.filter(pub_date=datetime(2005, 7, 27)).latest(), a3
        )

    def test_latest_sliced_queryset(self):
        msg = "Cannot change a query once a slice has been taken."
        with self.assertRaisesMessage(TypeError, msg):
            Article.objects.all()[0:5].latest()

    def test_latest_manual(self):
        # You can still use latest() with a model that doesn't have
        # "get_latest_by" set -- just pass in the field name manually.
        Person.objects.create(name="Ralph", birthday=datetime(1950, 1, 1))
        p2 = Person.objects.create(name="Stephanie", birthday=datetime(1960, 2, 3))
        msg = (
            "earliest() and latest() require either fields as positional arguments "
            "or 'get_latest_by' in the model's Meta."
        )
        with self.assertRaisesMessage(ValueError, msg):
            Person.objects.latest()
        self.assertEqual(Person.objects.latest("birthday"), p2)


class TestFirstLast(TestCase):
    def test_first(self):
        p1 = Person.objects.create(name="Bob", birthday=datetime(1950, 1, 1))
        p2 = Person.objects.create(name="Alice", birthday=datetime(1961, 2, 3))
        self.assertEqual(Person.objects.first(), p1)
        self.assertEqual(Person.objects.order_by("name").first(), p2)
        self.assertEqual(
            Person.objects.filter(birthday__lte=datetime(1955, 1, 1)).first(), p1
        )
        self.assertIsNone(
            Person.objects.filter(birthday__lte=datetime(1940, 1, 1)).first()
        )

    def test_last(self):
        p1 = Person.objects.create(name="Alice", birthday=datetime(1950, 1, 1))
        p2 = Person.objects.create(name="Bob", birthday=datetime(1960, 2, 3))
        # Note: by default PK ordering.
        self.assertEqual(Person.objects.last(), p2)
        self.assertEqual(Person.objects.order_by("-name").last(), p1)
        self.assertEqual(
            Person.objects.filter(birthday__lte=datetime(1955, 1, 1)).last(), p1
        )
        self.assertIsNone(
            Person.objects.filter(birthday__lte=datetime(1940, 1, 1)).last()
        )

    def test_index_error_not_suppressed(self):
        """
        #23555 -- Unexpected IndexError exceptions in QuerySet iteration
        shouldn't be suppressed.
        """

        def check():
            # We know that we've broken the __iter__ method, so the queryset
            # should always raise an exception.
            with self.assertRaises(IndexError):
                IndexErrorArticle.objects.all()[:10:2]
            with self.assertRaises(IndexError):
                IndexErrorArticle.objects.first()
            with self.assertRaises(IndexError):
                IndexErrorArticle.objects.last()

        check()

        # And it does not matter if there are any records in the DB.
        IndexErrorArticle.objects.create(
            headline="Article 1",
            pub_date=datetime(2005, 7, 26),
            expire_date=datetime(2005, 9, 1),
        )
        check()

    def test_first_last_unordered_qs_aggregation_error(self):
        a1 = Article.objects.create(
            headline="Article 1",
            pub_date=datetime(2005, 7, 26),
            expire_date=datetime(2005, 9, 1),
        )
        Comment.objects.create(article=a1, likes_count=5)

        qs = Comment.objects.values("article").annotate(avg_likes=Avg("likes_count"))
        msg = (
            "Cannot use QuerySet.%s() on an unordered queryset performing aggregation. "
            "Add an ordering with order_by()."
        )
        with self.assertRaisesMessage(TypeError, msg % "first"):
            qs.first()
        with self.assertRaisesMessage(TypeError, msg % "last"):
            qs.last()