django/tests/db_functions/test_trim.py

from django.db.models import CharField
from django.db.models.functions import LTrim, RTrim, Trim
from django.test import TestCase

from .models import Author


class TrimTests(TestCase):
    def test_trim(self):
        Author.objects.create(name='  John ', alias='j')
        Author.objects.create(name='Rhonda', alias='r')
        authors = Author.objects.annotate(
            ltrim=LTrim('name'),
            rtrim=RTrim('name'),
            trim=Trim('name'),
        )
        self.assertQuerysetEqual(
            authors.order_by('alias'), [
                ('John ', '  John', 'John'),
                ('Rhonda', 'Rhonda', 'Rhonda'),
            ],
            lambda a: (a.ltrim, a.rtrim, a.trim)
        )

    def test_trim_transform(self):
        Author.objects.create(name=' John  ')
        Author.objects.create(name='Rhonda')
        tests = (
            (LTrim, 'John  '),
            (RTrim, ' John'),
            (Trim, 'John'),
        )
        for transform, trimmed_name in tests:
            with self.subTest(transform=transform):
                try:
                    CharField.register_lookup(transform)
                    authors = Author.objects.filter(**{'name__%s' % transform.lookup_name: trimmed_name})
                    self.assertQuerysetEqual(authors, [' John  '], lambda a: a.name)
                finally:
                    CharField._unregister_lookup(transform)