Fixed #21741 -- Fixed render_to_string to stop pushing empty dictionaries to its Context

Thanks to kezabelle for the report and original patch
and to numerodix for his improved patch.

3 files changed, 19 insertions, 0 deletions

diff --git a/tests/template_tests/templates/test_context_stack.html b/tests/template_tests/templates/test_context_stack.html
new file mode 100644
index 0000000000..c5097c5e66
--- /dev/null
+++ b/tests/template_tests/templates/test_context_stack.html
@@ -0,0 +1,2 @@
+{% load custom %}
+{% context_stack_length %}
diff --git a/tests/template_tests/templatetags/custom.py b/tests/template_tests/templatetags/custom.py
index 9aa51931e0..16e8e3e26a 100644
--- a/tests/template_tests/templatetags/custom.py
+++ b/tests/template_tests/templatetags/custom.py
@@ -22,6 +22,11 @@ def noop(value, param=None):
     return value
 
 
+@register.simple_tag(takes_context=True)
+def context_stack_length(context):
+    return len(context.dicts)
+
+
 @register.simple_tag
 def no_params():
     """Expected no_params __doc__"""
diff --git a/tests/template_tests/test_loaders.py b/tests/template_tests/test_loaders.py
index 5f9306b33b..f89b9803e4 100644
--- a/tests/template_tests/test_loaders.py
+++ b/tests/template_tests/test_loaders.py
@@ -171,6 +171,18 @@ class RenderToStringTest(TestCase):
             'No template names provided$',
             loader.select_template, [])
 
+    def test_no_empty_dict_pushed_to_stack(self):
+        """
+        No empty dict should be pushed to the context stack when render_to_string
+        is called without any argument (#21741).
+        """
+
+        # The stack should have a length of 1, corresponding to the builtins
+        self.assertEqual('1',
+            loader.render_to_string('test_context_stack.html').strip())
+        self.assertEqual('1',
+            loader.render_to_string('test_context_stack.html', context_instance=Context()).strip())
+
 
 class TemplateDirsOverrideTest(unittest.TestCase):