[1.5.x] Fixed #19280 -- Raised an explicit exception for the old {% url %} syntax.

Backport of 6b8a7ce.

django/template/defaulttags.py

@@ -398,6 +398,10 @@ class URLNode(Node):
 
         view_name = self.view_name.resolve(context)
 
+        if not view_name:
+            raise TemplateSyntaxError("'url' takes requires a non-empty first"
+                " argument. The syntax changed in Django 1.5, see the docs.")
+
         # Try to look up the URL twice: once given the view name, and again
         # relative to what we guess is the "main" app. If they both fail,
         # re-raise the NoReverseMatch unless we're using the

docs/ref/templates/builtins.txt

@@ -1024,6 +1024,16 @@ This will follow the normal :ref:`namespaced URL resolution strategy
 <topics-http-reversing-url-namespaces>`, including using any hints provided
 by the context as to the current application.
 
+.. warning::
+
+    Don't forget to put quotes around the function path or pattern name!
+
+    .. versionchanged:: 1.5
+        The first paramater used not to be quoted, which was inconsistent with
+        other template tags. Since Django 1.5, it is evaluated according to
+        the usual rules: it can be a quoted string or a variable that will be
+        looked up in the context.
+
 .. templatetag:: verbatim
 
 verbatim

tests/regressiontests/templates/tests.py

@@ -19,7 +19,8 @@ except ImportError:     # Python 2
     from urlparse import urljoin
 
 from django import template
-from django.template import base as template_base, RequestContext, Template, Context
+from django.template import (base as template_base, Context, RequestContext,
+    Template, TemplateSyntaxError)
 from django.core import urlresolvers
 from django.template import loader
 from django.template.loaders import app_directories, filesystem, cached
@@ -364,6 +365,14 @@ class Templates(TestCase):
         with self.assertRaises(urlresolvers.NoReverseMatch):
             t.render(c)
 
+    def test_url_explicit_exception_for_old_syntax(self):
+        # Regression test for #19280
+        t = Template('{% url path.to.view %}')      # not quoted = old syntax
+        c = Context()
+        with self.assertRaisesRegexp(TemplateSyntaxError,
+                "The syntax changed in Django 1.5, see the docs."):
+            t.render(c)
+
     @override_settings(DEBUG=True, TEMPLATE_DEBUG=True)
     def test_no_wrapped_exception(self):
         """