RUBY-341 fix :max_scan and :show_disk_loc

lib/mongo/collection.rb

@@ -217,7 +217,7 @@ module Mongo
       max_scan   = opts.delete(:max_scan)
       return_key = opts.delete(:return_key)
       transformer = opts.delete(:transformer)
-      show_disk_loc = opts.delete(:max_scan)
+      show_disk_loc = opts.delete(:show_disk_loc)
       read          = opts.delete(:read) || @read_preference
 
       if timeout == false && !block_given?

lib/mongo/cursor.rb

@@ -26,7 +26,7 @@ module Mongo
     attr_reader :collection, :selector, :fields,
       :order, :hint, :snapshot, :timeout,
       :full_collection_name, :transformer,
-      :options, :cursor_id
+      :options, :cursor_id, :show_disk_loc
 
     # Create a new cursor.
     #
@@ -600,7 +600,7 @@ module Mongo
       spec['$hint']     = @hint if @hint && @hint.length > 0
       spec['$explain']  = true if @explain
       spec['$snapshot'] = true if @snapshot
-      spec['$maxscan']  = @max_scan if @max_scan
+      spec['$maxScan']  = @max_scan if @max_scan
       spec['$returnKey']   = true if @return_key
       spec['$showDiskLoc'] = true if @show_disk_loc
       spec
@@ -608,7 +608,8 @@ module Mongo
 
     # Returns true if the query contains order, explain, hint, or snapshot.
     def query_contains_special_fields?
-      @order || @explain || @hint || @snapshot
+      @order || @explain || @hint || @snapshot || @show_disk_loc ||
+        @max_scan || @return_key
     end
 
     def close_cursor_if_query_complete

test/collection_test.rb

@@ -705,6 +705,26 @@ class TestCollection < Test::Unit::TestCase
     coll.ensure_index([['a', 1]])
   end
 
+
+  if @@version > '2.0.0'
+    def test_show_disk_loc
+      @@test.save({:a => 1})
+      @@test.save({:a => 2})
+      assert @@test.find({:a => 1}, :show_disk_loc => true).show_disk_loc
+      assert @@test.find({:a => 1}, :show_disk_loc => true).next['$diskLoc']
+      @@test.remove
+    end
+
+    def test_max_scan
+      1000.times do |n|
+        @@test.save({:a => n})
+      end
+      assert @@test.find({:a => 999}).next
+      assert !@@test.find({:a => 999}, :max_scan => 500).next
+      @@test.remove
+    end
+  end
+
   context "Grouping" do
     setup do
       @@test.remove