Add error mode switching

lib/liquid/tags/if.rb

@@ -29,6 +29,7 @@ module Liquid
     end
 
     def render(context)
+      context.errors += @warnings if @warnings
       context.stack do
         @blocks.each do |block|
           if block.evaluate(context)
@@ -52,7 +53,22 @@ module Liquid
         @nodelist = block.attach(Array.new)
       end
 
-      def old_parse(markup)
+      def parse_condition(markup)
+        case Template.error_mode
+        when :strict then strict_parse(markup)
+        when :lax    then lax_parse(markup)
+        when :warn
+          begin
+            return strict_parse(markup)
+          rescue SyntaxError => e
+            @warnings ||= []
+            @warnings << e
+            return lax_parse(markup)
+          end
+        end
+      end
+
+      def lax_parse(markup)
         expressions = markup.scan(ExpressionsAndOperators).reverse
         raise(SyntaxError, SyntaxHelp) unless expressions.shift =~ Syntax
 
@@ -71,7 +87,7 @@ module Liquid
         condition
       end
 
-      def parse_condition(markup)
+      def strict_parse(markup)
         p = Parser.new(markup)
 
         condition = parse_comparison(p)

lib/liquid/template.rb

@@ -34,6 +34,18 @@ module Liquid
         @tags ||= {}
       end
 
+      # Sets how strict the parser should be.
+      # :lax acts like liquid 2.5 and silently ignores malformed tags in most cases.
+      # :warn is the default and will give deprecation warnings when invalid syntax is used.
+      # :strict will enforce correct syntax.
+      def error_mode=(mode)
+        @error_mode = mode
+      end
+
+      def error_mode
+        @error_mode || :warn
+      end
+
       # Pass a module with filter methods which should be available
       # to all liquid views. Good for registering the standard library
       def register_filter(mod)

lib/liquid/variable.rb

@@ -17,11 +17,24 @@ module Liquid
     def initialize(markup)
       @markup  = markup
       @name    = nil
-      @filters = []
-      parse(markup)
+      @warning = nil
+      
+
+      case Template.error_mode
+      when :strict then strict_parse(markup)
+      when :lax    then lax_parse(markup)
+      when :warn
+        begin
+          strict_parse(markup)
+        rescue SyntaxError => e
+          @warning = e
+          lax_parse(markup)
+        end
+      end
     end
 
-    def old_parse(markup)
+    def lax_parse(markup)
+      @filters = []
       if match = markup.match(/\s*(#{QuotedFragment})(.*)/o)
         @name = match[1]
         if match[2].match(/#{FilterSeparator}\s*(.*)/o)
@@ -37,7 +50,8 @@ module Liquid
       end
     end
 
-    def parse(markup)
+    def strict_parse(markup)
+      @filters = []
       p = Parser.new(markup)
       # Could be just filters with no input
       @name = p.look(:pipe) ? '' : p.expression
@@ -61,6 +75,7 @@ module Liquid
 
     def render(context)
       return '' if @name.nil?
+      context.errors << @warning if @warning
       @filters.inject(context[@name]) do |output, filter|
         filterargs = []
         keyword_args = {}