Support filters in set block

- e.g {% set foo | trim %}...{% endset %}
- closes #486

jinja2/compiler.py

@@ -1412,7 +1412,11 @@ def visit_AssignBlock(self, node, frame):
         assignment_frame = self.make_assignment_frame(frame)
         self.newline(node)
         self.visit(node.target, assignment_frame)
-        self.write(' = concat(%s)' % block_frame.buffer)
+        if node.filter is not None:
+            self.write(' = ')
+            self.visit_Filter(node.filter, block_frame)
+        else:
+            self.write(' = concat(%s)' % block_frame.buffer)
         self.export_assigned_vars(frame, assignment_frame)
 
     # -- Expression Visitors

jinja2/nodes.py

@@ -349,7 +349,7 @@ class Assign(Stmt):
 
 class AssignBlock(Stmt):
     """Assigns a block to a target."""
-    fields = ('target', 'body')
+    fields = ('target', 'filter', 'body')
 
 
 class Expr(Node):

jinja2/parser.py

@@ -171,9 +171,10 @@ def parse_set(self):
         if self.stream.skip_if('assign'):
             expr = self.parse_tuple()
             return nodes.Assign(target, expr, lineno=lineno)
+        filter_node = self.parse_filter(None)
         body = self.parse_statements(('name:endset',),
                                      drop_needle=True)
-        return nodes.AssignBlock(target, body, lineno=lineno)
+        return nodes.AssignBlock(target, filter_node, body, lineno=lineno)
 
     def parse_for(self):
         """Parse a for loop."""

tests/test_core_tags.py

@@ -335,3 +335,10 @@ def test_block(self, env_trim):
         tmpl = env_trim.from_string('{% set foo %}42{% endset %}{{ foo }}')
         assert tmpl.render() == '42'
         assert tmpl.module.foo == u'42'
+
+    def test_block_filtered(self, env_trim):
+        tmpl = env_trim.from_string(
+            '{% set foo | trim | length | string %} 42    {% endset %}'
+            '{{ foo }}')
+        assert tmpl.render() == '2'
+        assert tmpl.module.foo == u'2'