fixed bugs with serializing and deserializing js code with scope

lib/bson/code_with_scope.rb

@@ -89,10 +89,13 @@ def initialize(javascript = "", scope = {})
     #
     # @since 2.0.0
     def to_bson(encoded = ''.force_encoding(BINARY))
-      encode_with_placeholder_and_null(BSON_ADJUST, encoded) do |encoded|
+      # -1 because we are removing an extra byte
+      out = encode_with_placeholder_and_null(BSON_ADJUST - 1, encoded) do |encoded|
         javascript.to_bson(encoded)
         scope.to_bson(encoded)
       end
+      # an extra null byte has been added; we must remove it
+      out.chop!
     end
 
     # Deserialize a code with scope from BSON.
@@ -105,9 +108,18 @@ def to_bson(encoded = ''.force_encoding(BINARY))
     #
     # @since 2.0.0
     def self.from_bson(bson)
-      code_with_scope = StringIO.new(bson.read(Int32.from_bson(bson)))
-      length = code_with_scope.read(4).unpack(Int32::PACK).first
-      new(code_with_scope.read(length).from_bson_string.chop!)
+      cws_total_length = Int32.from_bson(bson) - 4 #deduct the size of the int we just read
+      code_with_scope = StringIO.new(bson.read(cws_total_length))
+      code_length = code_with_scope.read(4).unpack(Int32::PACK).first
+      bson_code = code_with_scope.read(code_length).from_bson_string.chop!
+
+      scope_length_str = code_with_scope.read(4) 
+      scope_length = scope_length_str.unpack(Int32::PACK).first
+      bson_scope_str = code_with_scope.read(scope_length)
+
+      # reconstruct the whole thing, since Hash throws away first 4 bytes
+      bson_scope = ::Hash.from_bson(StringIO.new(scope_length_str + bson_scope_str))
+      new(bson_code, bson_scope)
     end
 
     # Register this type when the module is loaded.

lib/bson/hash.rb

@@ -31,7 +31,7 @@ module Hash
     # Get the hash as encoded BSON.
     #
     # @example Get the hash as encoded BSON.
-    #   { field: "value" }.to_bson
+    #   { "field" => "value" }.to_bson
     #
     # @return [ String ] The encoded string.
     #
@@ -52,7 +52,7 @@ module ClassMethods
 
       # Deserialize the hash from BSON.
       #
-      # @param [ String ] bson The bson representing a hash.
+      # @param [ IO ] bson The bson representing a hash.
       #
       # @return [ Array ] The decoded hash.
       #

lib/bson/string.rb

@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 # Copyright (C) 2013 10gen Inc.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");

spec/bson/code_with_scope_spec.rb

@@ -40,8 +40,8 @@
     end
     let(:obj) { described_class.new(code, scope) }
     let(:bson) do
-      "#{48.to_bson}#{(code.length + 1).to_bson}#{code}#{BSON::NULL_BYTE}" +
-      "#{scope.to_bson}#{BSON::NULL_BYTE}"
+      "#{47.to_bson}#{(code.length + 1).to_bson}#{code}#{BSON::NULL_BYTE}" +
+      "#{scope.to_bson}"
     end
 
     it_behaves_like "a bson element"
@@ -53,7 +53,7 @@
     let(:type) { 15.chr }
     let(:code) { "this.value == name" }
     let(:scope) do
-      { :name => "test" }
+      { "name" => "test" }
     end
     let(:obj) { described_class.new(code, scope) }
     let(:bson) { StringIO.new(obj.to_bson) }
@@ -63,8 +63,8 @@
       expect(deserialized.javascript).to eq(code)
     end
 
-    it "does not deserialize a scope" do
-      expect(deserialized.scope).to be_empty
+    it "deserializes the scope" do
+      expect(deserialized.scope).to eq(scope)
     end
   end
 end