Merge pull request #691 from urbandictionary/missing_variables_and_filters

Merge pull request 691

lib/liquid/block_body.rb

@@ -76,6 +76,9 @@ module Liquid
           end
         rescue MemoryError => e
           raise e
+        rescue UndefinedVariable, UndefinedDropMethod, UndefinedFilter => e
+          context.handle_error(e, token.line_number)
+          output << nil
         rescue ::StandardError => e
           output << context.handle_error(e, token.line_number)
         end

lib/liquid/context.rb

@@ -13,7 +13,7 @@ module Liquid
   #   context['bob']  #=> nil  class Context
   class Context
     attr_reader :scopes, :errors, :registers, :environments, :resource_limits
-    attr_accessor :exception_handler, :template_name, :partial, :global_filter
+    attr_accessor :exception_handler, :template_name, :partial, :global_filter, :strict_variables, :strict_filters
 
     def initialize(environments = {}, outer_scope = {}, registers = {}, rethrow_errors = false, resource_limits = nil)
       @environments     = [environments].flatten
@@ -207,6 +207,8 @@ module Liquid
     def lookup_and_evaluate(obj, key)
       if (value = obj[key]).is_a?(Proc) && obj.respond_to?(:[]=)
         obj[key] = (value.arity == 0) ? value.call : value.call(self)
+      elsif strict_variables && obj.respond_to?(:key?) && !obj.key?(key)
+        raise Liquid::UndefinedVariable, "undefined variable #{key}"
       else
         value
       end

lib/liquid/drop.rb

@@ -24,8 +24,9 @@ module Liquid
     attr_writer :context
 
     # Catch all for the method
-    def liquid_method_missing(_method)
-      nil
+    def liquid_method_missing(method)
+      return nil unless @context.strict_variables
+      raise Liquid::UndefinedDropMethod, "undefined method #{method}"
     end
 
     # called by liquid to invoke a drop

lib/liquid/errors.rb

@@ -56,4 +56,7 @@ module Liquid
   MemoryError = Class.new(Error)
   ZeroDivisionError = Class.new(Error)
   FloatDomainError = Class.new(Error)
+  UndefinedVariable = Class.new(Error)
+  UndefinedDropMethod = Class.new(Error)
+  UndefinedFilter = Class.new(Error)
 end

lib/liquid/strainer.rb

@@ -26,7 +26,7 @@ module Liquid
     end
 
     def self.add_filter(filter)
-      raise ArgumentError, "Expected module but got: #{f.class}" unless filter.is_a?(Module)
+      raise ArgumentError, "Expected module but got: #{filter.class}" unless filter.is_a?(Module)
       unless self.class.include?(filter)
         send(:include, filter)
         @filter_methods.merge(filter.public_instance_methods.map(&:to_s))
@@ -48,6 +48,8 @@ module Liquid
     def invoke(method, *args)
       if self.class.invokable?(method)
         send(method, *args)
+      elsif @context && @context.strict_filters
+        raise Liquid::UndefinedFilter, "undefined filter #{method}"
       else
         args.first
       end

lib/liquid/template.rb

@@ -181,12 +181,7 @@ module Liquid
 
         registers.merge!(options[:registers]) if options[:registers].is_a?(Hash)
 
-        context.add_filters(options[:filters]) if options[:filters]
-
-        context.global_filter = options[:global_filter] if options[:global_filter]
-
-        context.exception_handler = options[:exception_handler] if options[:exception_handler]
-
+        apply_options_to_context(context, options)
       when Module, Array
         context.add_filters(args.pop)
       end
@@ -235,5 +230,13 @@ module Liquid
         yield
       end
     end
+
+    def apply_options_to_context(context, options)
+      context.add_filters(options[:filters]) if options[:filters]
+      context.global_filter = options[:global_filter] if options[:global_filter]
+      context.exception_handler = options[:exception_handler] if options[:exception_handler]
+      context.strict_variables = options[:strict_variables] if options[:strict_variables]
+      context.strict_filters = options[:strict_filters] if options[:strict_filters]
+    end
   end
 end

lib/liquid/variable_lookup.rb

@@ -55,9 +55,11 @@ module Liquid
           object = object.send(key).to_liquid
 
           # No key was present with the desired value and it wasn't one of the directly supported
-          # keywords either. The only thing we got left is to return nil
+          # keywords either. The only thing we got left is to return nil or
+          # raise an exception if `strict_variables` option is set to true
         else
-          return nil
+          return nil unless context.strict_variables
+          raise Liquid::UndefinedVariable, "undefined variable #{key}"
         end
 
         # If we are dealing with a drop here we have to