Fixed #15791 - method to signal that callable objects should not be called in templates

Thanks to ejucovy for the suggestion and patch!

git-svn-id: http://code.djangoproject.com/svn/django/trunk@16045 bcc190cf-cafb-0310-a4f2-bffc1f526a37

2 files changed, 112 insertions, 0 deletions

diff --git a/tests/regressiontests/templates/callables.py b/tests/regressiontests/templates/callables.py
new file mode 100644
index 0000000000..8afa703f63
--- /dev/null
+++ b/tests/regressiontests/templates/callables.py
@@ -0,0 +1,111 @@
+from django import template
+from django.utils.unittest import TestCase
+
+class CallableVariablesTests(TestCase):
+
+    def test_callable(self):
+
+        class Doodad(object):
+            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 = template.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 = template.Template('{{ my_doodad.value }}')
+        self.assertEqual(t.render(c), u'')
+
+        # 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 = template.Template('{{ my_doodad.the_value }}')
+        self.assertEqual(t.render(c), u'42')
+        self.assertEqual(my_doodad.num_calls, 2)
+
+    def test_alters_data(self):
+
+        class Doodad(object):
+            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 = template.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 TEMPLATE_STRING_IF_INVALID
+        t = template.Template('{{ my_doodad.value }}')
+        self.assertEqual(t.render(c), u'')
+        t = template.Template('{{ my_doodad.the_value }}')
+        self.assertEqual(t.render(c), u'')
+
+        # 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(self):
+
+        class Doodad(object):
+            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 = template.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 = template.Template('{{ my_doodad.value }}')
+        self.assertEqual(t.render(c), u'42')
+        t = template.Template('{{ my_doodad.the_value }}')
+        self.assertEqual(t.render(c), u'')
+
+        # 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(object):
+            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 = template.Context({"my_doodad": my_doodad})
+
+        t = template.Template('{{ my_doodad.value }}')
+        self.assertEqual(t.render(c), u'42')
+        t = template.Template('{{ my_doodad.the_value }}')
+        self.assertEqual(t.render(c), u'')
+
+        # Double-check that the object was really never called during the
+        # template rendering.
+        self.assertEqual(my_doodad.num_calls, 0)
diff --git a/tests/regressiontests/templates/tests.py b/tests/regressiontests/templates/tests.py
index dedd7d5c92..75f3b4f412 100644
--- a/tests/regressiontests/templates/tests.py
+++ b/tests/regressiontests/templates/tests.py
@@ -25,6 +25,7 @@ from django.utils.translation import activate, deactivate, ugettext as _
 from django.utils.safestring import mark_safe
 from django.utils.tzinfo import LocalTimezone
 
+from callables import *
 from context import ContextTests
 from custom import CustomTagTests, CustomFilterTests
 from parser import ParserTests