prefix for Liquid::Error instances

lib/liquid/errors.rb

@@ -1,22 +1,18 @@
 module Liquid
   class Error < ::StandardError
     attr_accessor :line_number
+    attr_accessor :markup_context
 
-    def self.render(e)
+    def to_s(with_prefix=true)
       str = ""
+      str << message_prefix if with_prefix
+      str << super()
 
-      if e.is_a?(SyntaxError)
-        str << "Liquid syntax error"
-      else
-        str << "Liquid error"
+      if markup_context
+        str << " "
+        str << markup_context
       end
 
-      if e.respond_to?(:line_number) && e.line_number
-        str << " (line #{e.line_number})"
-      end
-
-      str << ": "
-      str << e.message
       str
     end
 
@@ -24,6 +20,32 @@ module Liquid
       return unless token.respond_to?(:line_number)
       self.line_number = token.line_number
     end
+
+    def self.render(e)
+      if e.is_a?(Liquid::Error)
+        e.to_s
+      else
+        "Liquid error: #{e.to_s}"
+      end
+    end
+
+    private
+
+    def message_prefix
+      str = ""
+      if is_a?(SyntaxError)
+        str << "Liquid syntax error"
+      else
+        str << "Liquid error"
+      end
+
+      if line_number
+        str << " (line #{line_number})"
+      end
+
+      str << ": "
+      str
+    end
   end
 
   class ArgumentError < Error; end