Fixed #19819 - Improved template filter errors handling.

Wrap the Parser.compile_filter method call with a try/except and call the
newly added Parser.compile_filter_error(). Overwrite this method in the
DebugParser to throw the correct error.

Since this error was otherwise catched by the compile_function try/except
block the debugger highlighted the wrong line.

django/template/base.py

@@ -250,7 +250,11 @@ class Parser(object):
             elif token.token_type == 1: # TOKEN_VAR
                 if not token.contents:
                     self.empty_variable(token)
-                filter_expression = self.compile_filter(token.contents)
+                try:
+                    filter_expression = self.compile_filter(token.contents)
+                except TemplateSyntaxError as e:
+                    if not self.compile_filter_error(token, e):
+                        raise
                 var_node = self.create_variable_node(filter_expression)
                 self.extend_nodelist(nodelist, var_node, token)
             elif token.token_type == 2: # TOKEN_BLOCK
@@ -330,6 +334,9 @@ class Parser(object):
     def unclosed_block_tag(self, parse_until):
         raise self.error(None, "Unclosed tags: %s " % ', '.join(parse_until))
 
+    def compile_filter_error(self, token, e):
+        pass
+
     def compile_function_error(self, token, e):
         pass
 

django/template/debug.py

@@ -64,6 +64,10 @@ class DebugParser(Parser):
         msg = "Unclosed tag '%s'. Looking for one of: %s " % (command, ', '.join(parse_until))
         raise self.source_error(source, msg)
 
+    def compile_filter_error(self, token, e):
+        if not hasattr(e, 'django_template_source'):
+            e.django_template_source = token.source
+
     def compile_function_error(self, token, e):
         if not hasattr(e, 'django_template_source'):
             e.django_template_source = token.source

tests/regressiontests/templates/parser.py

@@ -4,8 +4,10 @@ Testing some internals of the template processing. These are *not* examples to b
 from __future__ import unicode_literals
 
 from django.template import (TokenParser, FilterExpression, Parser, Variable,
-    TemplateSyntaxError)
+    Template, TemplateSyntaxError)
+from django.test.utils import override_settings
 from django.utils.unittest import TestCase
+from django.utils import six
 
 
 class ParserTests(TestCase):
@@ -83,3 +85,11 @@ class ParserTests(TestCase):
         self.assertRaises(TemplateSyntaxError,
             Variable, "article._hidden"
         )
+
+    @override_settings(DEBUG=True, TEMPLATE_DEBUG=True)
+    def test_compile_filter_error(self):
+        # regression test for #19819
+        msg = "Could not parse the remainder: '@bar' from 'foo@bar'"
+        with six.assertRaisesRegex(self, TemplateSyntaxError, msg) as cm:
+            Template("{% if 1 %}{{ foo@bar }}{% endif %}")
+        self.assertEqual(cm.exception.django_template_source[1], (10, 23))