Hints are now BSON objects (probably ordered hashes) instead of arrays. Also make sure index exists for hint field in test.

lib/mongo/collection.rb

@@ -30,9 +30,9 @@ module XGen
           @name = name
         end
 
-        # Set hint fields to use and return +self+. hint may be a
-        # single field name, array of field names, or a hash whose keys will
-        # become the hint field names. May be +nil+.
+        # Set hint fields to use and return +self+. hint may be a single field
+        # name, array of field names, or a hash (preferably an OrderedHash).
+        # May be +nil+.
         def hint=(hint)
           @hint = normalize_hint_fields(hint)
           self
@@ -59,7 +59,7 @@ module XGen
           if hint
             hint = normalize_hint_fields(hint)
           else
-            hint = @hint
+            hint = @hint        # assumed to be normalized already
           end
           raise RuntimeError, "Unknown options [#{options.inspect}]" unless options.empty?
           @db.query(self, Query.new(selector, fields, offset, limit, sort, hint))
@@ -157,13 +157,15 @@ module XGen
         def normalize_hint_fields(hint)
           case hint
           when String
-            [hint]
+            {hint => 1}
           when Hash
-            hint.keys
+            hint
           when nil
             nil
           else
-            hint.to_a
+            h = OrderedHash.new
+            hint.to_a.each { |k| h[k] = 1 }
+            h
           end
         end
       end

lib/mongo/message/query_message.rb

@@ -44,14 +44,8 @@ module XGen
                                  raise "illegal order_by: is a #{query.order_by.class.name}, must be String, Array, Hash, or OrderedHash"
                                end
             end
-            if query.hint && query.hint.length > 0
-              hints = OrderedHash.new
-              query.hint.each { |hf| hints[hf] = 1 }
-              sel['$hint'] = hints
-            end
-            if query.explain
-              sel['$explain'] = true
-            end
+            sel['$hint'] = query.hint if query.hint && query.hint.length > 0
+            sel['$explain'] = true if query.explain
                                
           end
           write_doc(sel)

lib/mongo/query.rb

@@ -28,7 +28,7 @@ module XGen
         attr_accessor :number_to_skip, :number_to_return, :order_by
         # If true, $explain will be set in QueryMessage that uses this query.
         attr_accessor :explain
-        # Either +nil+ or an array of hint field names.
+        # Either +nil+ or a hash (preferably an OrderedHash).
         attr_accessor :hint
         attr_reader :selector   # writer defined below
 
@@ -59,7 +59,8 @@ module XGen
         #             is not preserved. (order_by is called :sort in calls to
         #             Collection#find.)
         #
-        # hint :: If not +nil+, specifies query hint fields. See
+        # hint :: If not +nil+, specifies query hint fields. Must be either
+        #                +nil+ or a hash (preferably an OrderedHash). See
         #                Collection#hint.
         def initialize(sel={}, return_fields=nil, number_to_skip=0, number_to_return=0, order_by=nil, hint=nil)
           @number_to_skip, @number_to_return, @order_by, @hint =

mongo-ruby-driver.gemspec

@@ -1,6 +1,6 @@
 Gem::Specification.new do |s|
   s.name = 'mongo'
-  s.version = '0.4.0'
+  s.version = '0.4.1'
   s.platform = Gem::Platform::RUBY
   s.summary = 'Simple pure-Ruby driver for the 10gen Mongo DB'
   s.description = 'A pure-Ruby driver for the 10gen Mongo DB. For more information about Mongo, see http://www.mongodb.org.'

tests/test_db_api.rb

@@ -373,6 +373,7 @@ class DBAPITest < Test::Unit::TestCase
   end
 
   def test_hint
+    @coll.create_index('test_a_index', 'a')
     begin
       assert_nil @coll.hint
       assert_equal 1, @coll.find({'a' => 1}, :hint => 'a').to_a.size
@@ -380,15 +381,15 @@ class DBAPITest < Test::Unit::TestCase
       assert_equal 1, @coll.find({'a' => 1}, :hint => {'a' => 1}).to_a.size
 
       @coll.hint = 'a'
-      assert_equal ['a'], @coll.hint
+      assert_equal({'a' => 1}, @coll.hint)
       assert_equal 1, @coll.find('a' => 1).to_a.size
 
       @coll.hint = ['a']
-      assert_equal ['a'], @coll.hint
+      assert_equal({'a' => 1}, @coll.hint)
       assert_equal 1, @coll.find('a' => 1).to_a.size
 
       @coll.hint = {'a' => 1}
-      assert_equal ['a'], @coll.hint
+      assert_equal({'a' => 1}, @coll.hint)
       assert_equal 1, @coll.find('a' => 1).to_a.size
 
       @coll.hint = nil
@@ -396,6 +397,8 @@ class DBAPITest < Test::Unit::TestCase
       assert_equal 1, @coll.find('a' => 1).to_a.size
     rescue => ex
       fail ex.to_s
+    ensure
+      @coll.drop_index('test_a_index')
     end
   end