+ Reenables the cache - now Context has a spec

lib/parslet/atoms/base.rb

@@ -1,3 +1,6 @@
+
+require 'parslet/atoms/context'
+
 # Base class for all parslets, handles orchestration of calls and implements
 # a lot of the operator and chaining methods.
 #
@@ -10,7 +13,7 @@ class Parslet::Atoms::Base
   #
   def parse(io)
     source = Parslet::Source.new(io)
-    context = Context.new
+    context = Parslet::Atoms::Context.new
 
     message = catch(:error) {
       result = apply(source, context)
@@ -238,66 +241,6 @@ def cause? # :nodoc:
     not @last_cause.nil?
   end
 private
-  # Helper class that implements a transient cache that maps position and
-  # parslet object to results. 
-  #
-  class Context
-    def initialize
-      @cache = Hash.new
-    end
-  
-    # Caches a parse answer for obj at source.pos. Applying the same parslet
-    # at one position of input always yields the same result, unless the input
-    # has changed. 
-    #
-    # We need the entire source here so we can ask for how many characters 
-    # were consumed by a successful parse. Imitation of such a parse must 
-    # advance the input pos by the same amount of bytes.
-    #
-    def cache(obj, source, &block)
-      yield
-    end
-    #   beg = source.pos
-    #       
-    #   # Not in cache yet? Return early.
-    #   unless entry = lookup(obj, beg)
-    #     result = yield
-    #   
-    #     set obj, beg, [result, source.pos-beg]
-    #     return result
-    #   end
-    # 
-    #   # the condition in unless has returned true, so entry is not nil.
-    #   result, advance = entry
-    # 
-    #   source.read(advance)
-    #   return result
-    # end  
-    
-    class Item
-      attr_reader :obj, :pos
-      def initialize(obj, pos)
-        @obj, @pos = obj, pos
-      end
-      def hash
-        @obj.hash - @pos
-      end
-      def eql?(o)
-        o.obj == self.obj && o.pos == self.pos
-      end
-    end
-
-  private 
-    def lookup(obj, pos)
-      i = Item.new(obj, pos)
-      @cache[i]
-    end
-    def set(obj, pos, val)
-      i = Item.new(obj, pos)
-      @cache[i] = val
-    end
-  end
-
   # Produces an instance of Success and returns it. 
   #
   def success(result)

lib/parslet/atoms/context.rb

@@ -0,0 +1,64 @@
+
+# Helper class that implements a transient cache that maps position and
+# parslet object to results. 
+#
+class Parslet::Atoms::Context
+  def initialize
+    @cache = Hash.new
+  end
+
+  # Caches a parse answer for obj at source.pos. Applying the same parslet
+  # at one position of input always yields the same result, unless the input
+  # has changed. 
+  #
+  # We need the entire source here so we can ask for how many characters 
+  # were consumed by a successful parse. Imitation of such a parse must 
+  # advance the input pos by the same amount of bytes.
+  #
+  def cache(obj, source, &block)
+    beg = source.pos
+
+    # Not in cache yet? Return early.
+    unless entry = lookup(obj, beg)
+      message = catch(:error) {
+        result = yield
+        set obj, beg, [true, result, source.pos-beg]
+        return result
+      }
+
+      set obj, beg, [false, message, source.pos-beg]
+      throw :error, message
+    end
+
+    # the condition in unless has returned true, so entry is not nil.
+    success, obj, advance = entry
+
+    source.read(advance)
+
+    throw :error, obj unless success
+    return obj
+  end  
+
+  class Item
+    attr_reader :obj, :pos
+    def initialize(obj, pos)
+      @obj, @pos = obj, pos
+    end
+    def hash
+      @obj.hash - @pos
+    end
+    def eql?(o)
+      o.obj == self.obj && o.pos == self.pos
+    end
+  end
+
+private 
+  def lookup(obj, pos)
+    i = Item.new(obj, pos)
+    @cache[i]
+  end
+  def set(obj, pos, val)
+    i = Item.new(obj, pos)
+    @cache[i] = val
+  end
+end

spec/parslet/atoms/base_spec.rb

@@ -2,7 +2,7 @@
 
 describe Parslet::Atoms::Base do
   let(:parslet) { Parslet::Atoms::Base.new }
-  let(:context) { Parslet::Atoms::Base::Context.new }
+  let(:context) { Parslet::Atoms::Context.new }
 
   describe "<- #try(io)" do
     it "should raise NotImplementedError" do

spec/parslet/atoms/context_spec.rb

@@ -0,0 +1,37 @@
+require 'spec_helper'
+
+require 'stringio'
+
+describe Parslet::Atoms::Context do
+  let(:source) { StringIO.new('foobar') }
+
+  context "when clean" do
+    it "should return whatever the block returns" do
+      subject.cache(self, source) { 1 }.should == 1
+    end 
+    it "should rethrow :error" do
+      lambda {
+        subject.cache(self, source) { throw :error, 'foo' }
+      }.should throw_symbol(:error, 'foo')
+    end 
+  end
+  context "when already called for obj and input position" do
+    context "(storing success, 1)" do
+      before(:each) { subject.cache(self, source) { 1 } }
+
+      it "should return cached result" do
+        subject.cache(self, source) { 2 }.should == 1
+      end 
+    end
+    context "(storing error, 'foo')" do
+      before(:each) { catch(:error) {
+        subject.cache(self, source) { throw :error, 'foo' }} }
+
+      it "should return cached result" do
+        lambda {
+          subject.cache(self, source) { 2 }
+        }.should throw_symbol(:error, 'foo')
+      end 
+    end
+  end
+end

spec/parslet/atoms_spec.rb

@@ -12,7 +12,7 @@ def not_parse
   extend Parslet
 
   def src(str); Parslet::Source.new str; end
-  let(:context) { Parslet::Atoms::Base::Context.new }
+  let(:context) { Parslet::Atoms::Context.new }
 
   describe "match('[abc]')" do
     attr_reader :parslet