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from unittest import TestCase
from django.db.models.utils import AltersData
from django.template import Context, Engine
class CallableVariablesTests(TestCase):
@classmethod
def setUpClass(cls):
cls.engine = Engine()
super().setUpClass()
def test_callable(self):
class Doodad:
def __init__(self, value):
self.num_calls = 0
self.value = value
def __call__(self):
self.num_calls += 1
return {"the_value": self.value}
my_doodad = Doodad(42)
c = Context({"my_doodad": my_doodad})
# We can't access ``my_doodad.value`` in the template, because
# ``my_doodad.__call__`` will be invoked first, yielding a dictionary
# without a key ``value``.
t = self.engine.from_string("{{ my_doodad.value }}")
self.assertEqual(t.render(c), "")
# We can confirm that the doodad has been called
self.assertEqual(my_doodad.num_calls, 1)
# But we can access keys on the dict that's returned
# by ``__call__``, instead.
t = self.engine.from_string("{{ my_doodad.the_value }}")
self.assertEqual(t.render(c), "42")
self.assertEqual(my_doodad.num_calls, 2)
def test_alters_data(self):
class Doodad:
alters_data = True
def __init__(self, value):
self.num_calls = 0
self.value = value
def __call__(self):
self.num_calls += 1
return {"the_value": self.value}
my_doodad = Doodad(42)
c = Context({"my_doodad": my_doodad})
# Since ``my_doodad.alters_data`` is True, the template system will not
# try to call our doodad but will use string_if_invalid
t = self.engine.from_string("{{ my_doodad.value }}")
self.assertEqual(t.render(c), "")
t = self.engine.from_string("{{ my_doodad.the_value }}")
self.assertEqual(t.render(c), "")
# Double-check that the object was really never called during the
# template rendering.
self.assertEqual(my_doodad.num_calls, 0)
def test_alters_data_propagation(self):
class GrandParentLeft(AltersData):
def my_method(self):
return 42
my_method.alters_data = True
class ParentLeft(GrandParentLeft):
def change_alters_data_method(self):
return 63
change_alters_data_method.alters_data = True
def sub_non_callable_method(self):
return 64
sub_non_callable_method.alters_data = True
class ParentRight(AltersData):
def other_method(self):
return 52
other_method.alters_data = True
class Child(ParentLeft, ParentRight):
def my_method(self):
return 101
def other_method(self):
return 102
def change_alters_data_method(self):
return 103
change_alters_data_method.alters_data = False
sub_non_callable_method = 104
class GrandChild(Child):
pass
child = Child()
self.assertIs(child.my_method.alters_data, True)
self.assertIs(child.other_method.alters_data, True)
self.assertIs(child.change_alters_data_method.alters_data, False)
grand_child = GrandChild()
self.assertIs(grand_child.my_method.alters_data, True)
self.assertIs(grand_child.other_method.alters_data, True)
self.assertIs(grand_child.change_alters_data_method.alters_data, False)
c = Context({"element": grand_child})
t = self.engine.from_string("{{ element.my_method }}")
self.assertEqual(t.render(c), "")
t = self.engine.from_string("{{ element.other_method }}")
self.assertEqual(t.render(c), "")
t = self.engine.from_string("{{ element.change_alters_data_method }}")
self.assertEqual(t.render(c), "103")
t = self.engine.from_string("{{ element.sub_non_callable_method }}")
self.assertEqual(t.render(c), "104")
def test_do_not_call(self):
class Doodad:
do_not_call_in_templates = True
def __init__(self, value):
self.num_calls = 0
self.value = value
def __call__(self):
self.num_calls += 1
return {"the_value": self.value}
my_doodad = Doodad(42)
c = Context({"my_doodad": my_doodad})
# Since ``my_doodad.do_not_call_in_templates`` is True, the template
# system will not try to call our doodad. We can access its attributes
# as normal, and we don't have access to the dict that it returns when
# called.
t = self.engine.from_string("{{ my_doodad.value }}")
self.assertEqual(t.render(c), "42")
t = self.engine.from_string("{{ my_doodad.the_value }}")
self.assertEqual(t.render(c), "")
# Double-check that the object was really never called during the
# template rendering.
self.assertEqual(my_doodad.num_calls, 0)
def test_do_not_call_and_alters_data(self):
# If we combine ``alters_data`` and ``do_not_call_in_templates``, the
# ``alters_data`` attribute will not make any difference in the
# template system's behavior.
class Doodad:
do_not_call_in_templates = True
alters_data = True
def __init__(self, value):
self.num_calls = 0
self.value = value
def __call__(self):
self.num_calls += 1
return {"the_value": self.value}
my_doodad = Doodad(42)
c = Context({"my_doodad": my_doodad})
t = self.engine.from_string("{{ my_doodad.value }}")
self.assertEqual(t.render(c), "42")
t = self.engine.from_string("{{ my_doodad.the_value }}")
self.assertEqual(t.render(c), "")
# Double-check that the object was really never called during the
# template rendering.
self.assertEqual(my_doodad.num_calls, 0)
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