Commit 61c102d0 authored by Josh Smeaton's avatar Josh Smeaton
Browse files

Fixed #24183 -- Fixed wrong comparisons in Substr

parent 7f20041b

django/db/models/functions.py

+2 −2
Original line number Diff line number Diff line
@@ -110,13 +110,13 @@ class Substr(Func): 
        pos: an integer > 0, or an expression returning an integer

        length: an optional number of characters to return

        """

        if not hasattr('pos', 'resolve_expression'):

        if not hasattr(pos, 'resolve_expression'):

            if pos < 1:

                raise ValueError("'pos' must be greater than 0")

            pos = Value(pos)

        expressions = [expression, pos]

        if length is not None:

            if not hasattr('length', 'resolve_expression'):

            if not hasattr(length, 'resolve_expression'):

                length = Value(length)

            expressions.append(length)

        super(Substr, self).__init__(*expressions, **extra)

tests/db_functions/tests.py

+12 −0
Original line number Diff line number Diff line
@@ -278,6 +278,18 @@ class FunctionTests(TestCase): 
        with six.assertRaisesRegex(self, ValueError, "'pos' must be greater than 0"):

            Author.objects.annotate(raises=Substr('name', 0))



    def test_substr_with_expressions(self):

        Author.objects.create(name='John Smith', alias='smithj')

        Author.objects.create(name='Rhonda')

        authors = Author.objects.annotate(name_part=Substr('name', V(5), V(3)))

        self.assertQuerysetEqual(

            authors.order_by('name'), [

                ' Sm',

                'da',

            ],

            lambda a: a.name_part

        )



    def test_nested_function_ordering(self):

        Author.objects.create(name='John Smith')

        Author.objects.create(name='Rhonda Simpson', alias='ronny')