Prevent template variable lookups from intiatiating a class

[Luoxzhg]

class A:
    def __init__(self, value): 
         pass
    attr="Hello"

from django.template import Template, Context
t = Template(" {{  A.attr }}")
output=t.render(Context({"A": A}))

the output should be "Hello", but it is string_if_invalid, i.e., empty string "" .

[Tim Graham]

​PR

[Tim Graham]

I understand the desire for the behavior change, however, the change could be backwards incompatible. Consider this case which will pass before the change but fail afterward:

@setup({'t': '{{ A.attr }}'})
def test_class_attribute(self):
    """Accessing an attribute of an instantiated class."""
    class A:

        def __init__(self):
            self.attr = 'Hello'

    self.assertEqual(self.engine.render_to_string('t', {'A': A}), 'Hello')

Is there any documentation to suggest ​the current behavior is incorrect?

[Carlton Gibson]

I think this is expected behaviour, that has a workaround.

#15791 added a check for a do_not_call_in_templates attribute on a callable.

Setting this to True in the example test case allows it to pass.

This is documented in the ​Variables and lookups section of the Template API docs.

Closing as a duplicate of #15791