django/tests/db_functions/text/test_chr.py

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

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):
        with register_lookup(IntegerField, 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],
            )