django/tests/db_functions/test_chr.py

from django.db.models import IntegerField
from django.db.models.functions import Chr, Left, Ord
from django.test import TestCase

from .models import Author


class ChrTests(TestCase):
    @classmethod
    def setUpTestData(cls):
        cls.john = Author.objects.create(name='John Smith', alias='smithj')
        cls.elena = Author.objects.create(name='Élena Jordan', alias='elena')
        cls.rhonda = Author.objects.create(name='Rhonda')

    def test_basic(self):
        authors = Author.objects.annotate(first_initial=Left('name', 1))
        self.assertCountEqual(authors.filter(first_initial=Chr(ord('J'))), [self.john])
        self.assertCountEqual(authors.exclude(first_initial=Chr(ord('J'))), [self.elena, self.rhonda])

    def test_non_ascii(self):
        authors = Author.objects.annotate(first_initial=Left('name', 1))
        self.assertCountEqual(authors.filter(first_initial=Chr(ord('É'))), [self.elena])
        self.assertCountEqual(authors.exclude(first_initial=Chr(ord('É'))), [self.john, self.rhonda])

    def test_transform(self):
        try:
            IntegerField.register_lookup(Chr)
            authors = Author.objects.annotate(name_code_point=Ord('name'))
            self.assertCountEqual(authors.filter(name_code_point__chr=Chr(ord('J'))), [self.john])
            self.assertCountEqual(authors.exclude(name_code_point__chr=Chr(ord('J'))), [self.elena, self.rhonda])
        finally:
            IntegerField._unregister_lookup(Chr)