Fixed #33036 -- Made simple_tag()/inclusion_tag() with takes_context raise TemplateSyntaxError when function has no parameters.

django/template/library.py

@@ -243,7 +243,7 @@ def parse_bits(parser, bits, params, varargs, varkw, defaults,
     keyword arguments.
     """
     if takes_context:
-        if params[0] == 'context':
+        if params and params[0] == 'context':
             params = params[1:]
         else:
             raise TemplateSyntaxError(

tests/template_tests/templatetags/custom.py

@@ -150,6 +150,17 @@ def simple_tag_without_context_parameter(arg):
 simple_tag_without_context_parameter.anything = "Expected simple_tag_without_context_parameter __dict__"
 
 
+@register.simple_tag(takes_context=True)
+def simple_tag_takes_context_without_params():
+    """Expected simple_tag_takes_context_without_params __doc__"""
+    return 'Expected result'
+
+
+simple_tag_takes_context_without_params.anything = (
+    'Expected simple_tag_takes_context_without_params __dict__'
+)
+
+
 @register.simple_tag(takes_context=True)
 def escape_naive(context):
     """A tag that doesn't even think about escaping issues"""

tests/template_tests/templatetags/inclusion.py

@@ -242,6 +242,17 @@ def inclusion_tag_without_context_parameter(arg):
 inclusion_tag_without_context_parameter.anything = "Expected inclusion_tag_without_context_parameter __dict__"
 
 
+@register.inclusion_tag('inclusion.html', takes_context=True)
+def inclusion_tag_takes_context_without_params():
+    """Expected inclusion_tag_takes_context_without_params __doc__"""
+    return {}
+
+
+inclusion_tag_takes_context_without_params.anything = (
+    'Expected inclusion_tag_takes_context_without_params __dict__'
+)
+
+
 @register.inclusion_tag('inclusion_extends1.html')
 def inclusion_extends1():
     return {}

tests/template_tests/test_custom.py

@@ -169,6 +169,16 @@ class SimpleTagTests(TagTestCase):
         with self.assertRaisesMessage(TemplateSyntaxError, msg):
             self.engine.from_string('{% load custom %}{% simple_tag_without_context_parameter 123 %}')
 
+    def test_simple_tag_missing_context_no_params(self):
+        msg = (
+            "'simple_tag_takes_context_without_params' is decorated with "
+            "takes_context=True so it must have a first argument of 'context'"
+        )
+        with self.assertRaisesMessage(TemplateSyntaxError, msg):
+            self.engine.from_string(
+                '{% load custom %}{% simple_tag_takes_context_without_params %}'
+            )
+
 
 class InclusionTagTests(TagTestCase):
 
@@ -256,6 +266,16 @@ class InclusionTagTests(TagTestCase):
         with self.assertRaisesMessage(TemplateSyntaxError, msg):
             self.engine.from_string('{% load inclusion %}{% inclusion_tag_without_context_parameter 123 %}')
 
+    def test_include_tag_missing_context_no_params(self):
+        msg = (
+            "'inclusion_tag_takes_context_without_params' is decorated with "
+            "takes_context=True so it must have a first argument of 'context'"
+        )
+        with self.assertRaisesMessage(TemplateSyntaxError, msg):
+            self.engine.from_string(
+                '{% load inclusion %}{% inclusion_tag_takes_context_without_params %}'
+            )
+
     def test_inclusion_tags_from_template(self):
         c = Context({'value': 42})