cache variable lookups

lib/liquid/context.rb

@@ -1,5 +1,6 @@
 module Liquid
 
+  
   # Context keeps the variable stack and resolves variables, as well as keywords
   #
   #   context['variable'] = 'testing'
@@ -24,6 +25,7 @@ module Liquid
       squash_instance_assigns_with_environments
 
       @interrupts = []
+      @variable_cache = {}
     end
 
     def strainer
@@ -77,17 +79,20 @@ module Liquid
 
     # Push new local scope on the stack. use <tt>Context#stack</tt> instead
     def push(new_scope={})
+      @variable_cache = {}
       @scopes.unshift(new_scope)
       raise StackLevelError, "Nesting too deep" if @scopes.length > 100
     end
 
     # Merge a hash of variables in the current local scope
     def merge(new_scopes)
+      @variable_cache = {}
       @scopes[0].merge!(new_scopes)
     end
 
     # Pop from the stack. use <tt>Context#stack</tt> instead
     def pop
+      @variable_cache = {}
       raise ContextError if @scopes.size == 1
       @scopes.shift
     end
@@ -101,69 +106,112 @@ module Liquid
     #
     #   context['var]  #=> nil
     def stack(new_scope={})
+      @variable_cache = {}
       push(new_scope)
       yield
     ensure
       pop
+      @variable_cache = {}
     end
 
     def clear_instance_assigns
+      @variable_cache = {}
       @scopes[0] = {}
     end
 
-    # Only allow String, Numeric, Hash, Array, Proc, Boolean or <tt>Liquid::Drop</tt>
-    def []=(key, value)
-      @scopes[0][key] = value
+
+    # Look up variable, either resolve directly after considering the name. We can directly handle
+    # Strings, digits, floats and booleans (true,false).
+    # If no match is made we lookup the variable in the current scope and
+    # later move up to the parent blocks to see if we can resolve the variable somewhere up the tree.
+    # Some special keywords return symbols. Those symbols are to be called on the rhs object in expressions
+    #
+    # Example:
+    #   products == empty #=> products.empty?
+    def resolve(key)        
+      case key
+      when nil, ""
+        return nil
+      when "blank"
+        return :blank?
+      when "empty"
+        return :empty?
+      end
+      
+      result = Parser.parse(key)   
+      stack = []
+
+      result.each do |(sym, value)|          
+
+        case sym
+        when :id
+          stack.push value
+        when :lookup
+          left = stack.pop
+          value = find_variable(left)
+          
+          stack.push(harden(value))
+        when :range
+          right = stack.pop.to_i
+          left  = stack.pop.to_i
+          
+          stack.push (left..right)
+        when :buildin
+          left = stack.pop
+          value = invoke_buildin(left, value)
+          
+          stack.push(harden(value))
+        when :call
+          left = stack.pop
+          right = stack.pop
+          value = lookup_and_evaluate(right, left)
+
+          stack.push(harden(value))
+        else 
+          raise "unknown #{sym}"
+        end
+      end
+
+      return stack.first
     end
 
-    def [](key)
-      resolve(key)
+
+    # Only allow String, Numeric, Hash, Array, Proc, Boolean or <tt>Liquid::Drop</tt>
+    def []=(key, value)
+      @variable_cache[key] = value
+      @scopes[0][key] = value
     end
 
     def has_key?(key)
       resolve(key) != nil
     end
 
-    private
-      LITERALS = {
-        nil => nil, 'nil' => nil, 'null' => nil, '' => nil,
-        'true'  => true,
-        'false' => false,
-        'blank' => :blank?,
-        'empty' => :empty?
-      }
+    alias_method :[], :resolve
 
-      # Look up variable, either resolve directly after considering the name. We can directly handle
-      # Strings, digits, floats and booleans (true,false).
-      # If no match is made we lookup the variable in the current scope and
-      # later move up to the parent blocks to see if we can resolve the variable somewhere up the tree.
-      # Some special keywords return symbols. Those symbols are to be called on the rhs object in expressions
-      #
-      # Example:
-      #   products == empty #=> products.empty?
-      def resolve(key)
-        if LITERALS.key?(key)
-          LITERALS[key]
+    private
+
+      def invoke_buildin(obj, key)
+        # as weird as this is, liquid unit tests demand that we prioritize hash lookups 
+        # to buildins. So if we got a hash and it has a :first element we need to call that 
+        # instead of sending the first message...
+
+        if obj.respond_to?(:has_key?) && obj.has_key?(key)
+          return lookup_and_evaluate(obj, key)
+        end
+
+        if obj.respond_to?(key) 
+          return obj.send(key)
         else
-          case key
-          when /^'(.*)'$/ # Single quoted strings
-            $1
-          when /^"(.*)"$/ # Double quoted strings
-            $1
-          when /^(-?\d+)$/ # Integer and floats
-            $1.to_i
-          when /^\((\S+)\.\.(\S+)\)$/ # Ranges
-            (resolve($1).to_i..resolve($2).to_i)
-          when /^(-?\d[\d\.]+)$/ # Floats
-            $1.to_f
-          else
-            variable(key)
-          end
+          return nil    
         end
       end
 
       # Fetches an object starting at the local scope and then moving up the hierachy
       def find_variable(key)
+        if val = @variable_cache[key]
+          return val
+        end
+
         scope = @scopes.find { |s| s.has_key?(key) }
 
         if scope.nil?
@@ -177,72 +225,36 @@ module Liquid
 
         scope     ||= @environments.last || @scopes.last
         variable  ||= lookup_and_evaluate(scope, key)
-
-        variable = variable.to_liquid
-        variable.context = self if variable.respond_to?(:context=)
+        @variable_cache[key] = variable
 
         return variable
       end
 
-      # Resolves namespaced queries gracefully.
-      #
-      # Example
-      #  @context['hash'] = {"name" => 'tobi'}
-      #  assert_equal 'tobi', @context['hash.name']
-      #  assert_equal 'tobi', @context['hash["name"]']
-      def variable(markup)
-        parts = markup.scan(VariableParser)
-        square_bracketed = /^\[(.*)\]$/
-
-        first_part = parts.shift
-
-        if first_part =~ square_bracketed
-          first_part = resolve($1)
-        end
-
-        if object = find_variable(first_part)
-
-          parts.each do |part|
-            part = resolve($1) if part_resolved = (part =~ square_bracketed)
-
-            # If object is a hash- or array-like object we look for the
-            # presence of the key and if its available we return it
-            if object.respond_to?(:[]) and
-              ((object.respond_to?(:has_key?) and object.has_key?(part)) or
-               (object.respond_to?(:fetch) and part.is_a?(Integer)))
-
-              # if its a proc we will replace the entry with the proc
-              res = lookup_and_evaluate(object, part)
-              object = res.to_liquid
-
-              # Some special cases. If the part wasn't in square brackets and
-              # no key with the same name was found we interpret following calls
-              # as commands and call them on the current object
-            elsif !part_resolved and object.respond_to?(part) and ['size', 'first', 'last'].include?(part)
-
-              object = object.send(part.intern).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
-            else
-              return nil
-            end
-
-            # If we are dealing with a drop here we have to
-            object.context = self if object.respond_to?(:context=)
-          end
-        end
-
-        object
-      end # variable
-
       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)
-        else
-          value
+        return nil unless obj.respond_to?(:[])
+        
+        if obj.is_a?(Array)
+          return nil unless key.is_a?(Integer)
         end
-      end # lookup_and_evaluate
+
+        value = obj[key]
+
+        if value.is_a?(Proc)      
+          # call the proc
+          value = (value.arity == 0) ? value.call : value.call(self)
+
+          # memozie if possible
+          obj[key] = value if obj.respond_to?(:[]=)
+        end
+
+        value
+      end
+
+      def harden(value)
+        value = value.to_liquid
+        value.context = self if value.respond_to?(:context=)
+        return value
+      end
 
       def squash_instance_assigns_with_environments
         @scopes.last.each_key do |k|
@@ -254,6 +266,7 @@ module Liquid
           end
         end
       end # squash_instance_assigns_with_environments
+
   end # Context
 
 end # Liquid