django/tests/db_functions/comparison/test_coalesce.py

from django.db.models import TextField
from django.db.models.functions import Coalesce, Lower
from django.test import TestCase
from django.utils import timezone

from ..models import Article, Author

lorem_ipsum = """
    Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod
    tempor incididunt ut labore et dolore magna aliqua."""


class CoalesceTests(TestCase):

    def test_basic(self):
        Author.objects.create(name='John Smith', alias='smithj')
        Author.objects.create(name='Rhonda')
        authors = Author.objects.annotate(display_name=Coalesce('alias', 'name'))
        self.assertQuerysetEqual(
            authors.order_by('name'), ['smithj', 'Rhonda'],
            lambda a: a.display_name
        )

    def test_gt_two_expressions(self):
        with self.assertRaisesMessage(ValueError, 'Coalesce must take at least two expressions'):
            Author.objects.annotate(display_name=Coalesce('alias'))

    def test_mixed_values(self):
        a1 = Author.objects.create(name='John Smith', alias='smithj')
        a2 = Author.objects.create(name='Rhonda')
        ar1 = Article.objects.create(
            title='How to Django',
            text=lorem_ipsum,
            written=timezone.now(),
        )
        ar1.authors.add(a1)
        ar1.authors.add(a2)
        # mixed Text and Char
        article = Article.objects.annotate(
            headline=Coalesce('summary', 'text', output_field=TextField()),
        )
        self.assertQuerysetEqual(
            article.order_by('title'), [lorem_ipsum],
            lambda a: a.headline
        )
        # mixed Text and Char wrapped
        article = Article.objects.annotate(
            headline=Coalesce(Lower('summary'), Lower('text'), output_field=TextField()),
        )
        self.assertQuerysetEqual(
            article.order_by('title'), [lorem_ipsum.lower()],
            lambda a: a.headline
        )

    def test_ordering(self):
        Author.objects.create(name='John Smith', alias='smithj')
        Author.objects.create(name='Rhonda')
        authors = Author.objects.order_by(Coalesce('alias', 'name'))
        self.assertQuerysetEqual(
            authors, ['Rhonda', 'John Smith'],
            lambda a: a.name
        )
        authors = Author.objects.order_by(Coalesce('alias', 'name').asc())
        self.assertQuerysetEqual(
            authors, ['Rhonda', 'John Smith'],
            lambda a: a.name
        )
        authors = Author.objects.order_by(Coalesce('alias', 'name').desc())
        self.assertQuerysetEqual(
            authors, ['John Smith', 'Rhonda'],
            lambda a: a.name
        )