Disallow filters with no variable in strict mode

lib/liquid/variable.rb

@@ -63,7 +63,7 @@ module Liquid
       @filters = []
       p = Parser.new(markup)
       # Could be just filters with no input
-      @name = p.look(:pipe) ? nil : Expression.parse(p.expression)
+      @name = Expression.parse(p.expression)
       while p.consume?(:pipe)
         filtername = p.consume(:id)
         filterargs = p.consume?(:colon) ? parse_filterargs(p) : []

test/integration/parsing_quirks_test.rb

@@ -28,11 +28,14 @@ class ParsingQuirksTest < Minitest::Test
 
   def test_error_on_empty_filter
     assert Template.parse("{{test}}")
-    assert Template.parse("{{|test}}")
+
+    with_error_mode(:lax) do
+      assert Template.parse("{{|test}}")
+    end
+
     with_error_mode(:strict) do
-      assert_raises(SyntaxError) do
-        Template.parse("{{test |a|b|}}")
-      end
+      assert_raises(SyntaxError) { Template.parse("{{|test}}") }
+      assert_raises(SyntaxError) { Template.parse("{{test |a|b|}}") }
     end
   end