Fixed #29060 -- Made {% firstof %} assign '' to the asvar if all inputs are false.

django/template/defaulttags.py

@@ -118,15 +118,16 @@ class FirstOfNode(Node):
         self.asvar = asvar
 
     def render(self, context):
+        first = ''
         for var in self.vars:
             value = var.resolve(context, ignore_failures=True)
             if value:
                 first = render_value_in_context(value, context)
-                if self.asvar:
-                    context[self.asvar] = first
-                    return ''
-                return first
-        return ''
+                break
+        if self.asvar:
+            context[self.asvar] = first
+            return ''
+        return first
 
 
 class ForNode(Node):

tests/template_tests/syntax_tests/test_firstof.py

@@ -82,3 +82,10 @@ class FirstOfTagTests(SimpleTestCase):
         output = self.engine.render_to_string('firstof15', ctx)
         self.assertEqual(ctx['myvar'], '2')
         self.assertEqual(output, '')
+
+    @setup({'firstof16': '{% firstof a b c as myvar %}'})
+    def test_all_false_arguments_asvar(self):
+        ctx = {'a': 0, 'b': 0, 'c': 0}
+        output = self.engine.render_to_string('firstof16', ctx)
+        self.assertEqual(ctx['myvar'], '')
+        self.assertEqual(output, '')