can drop an index using the same type of spec used to create an index

lib/mongo/collection.rb

@@ -497,6 +497,9 @@ module Mongo
     #
     # @core indexes
     def drop_index(name)
+      if name.is_a?(Array)
+        return drop_index(index_name(name))
+      end
       @cache[name.to_s] = nil
       @db.drop_index(@name, name)
     end
@@ -824,6 +827,14 @@ module Mongo
     end
 
     private
+  
+    def index_name(spec)
+      field_spec = parse_index_spec(spec)
+      index_information.each do |index|
+        return index[0] if index[1]['key'] == field_spec
+      end
+      nil
+    end
 
     def parse_index_spec(spec)
       field_spec = BSON::OrderedHash.new

test/collection_test.rb

@@ -762,6 +762,41 @@ class TestCollection < Test::Unit::TestCase
       assert_equal 1, @collection.size
     end
   end
+  
+  context "Drop index " do
+    setup do
+      @@db.drop_collection('test-collection')
+      @collection = @@db.collection('test-collection')
+    end
+
+    should "drop an index" do
+      @collection.create_index([['a', Mongo::ASCENDING]])
+      assert @collection.index_information['a_1']
+      @collection.drop_index([['a', Mongo::ASCENDING]])
+      assert_nil @collection.index_information['a_1']
+    end
+    
+    should "drop an index which was given a specific name" do
+      @collection.create_index([['a', Mongo::DESCENDING]], {:name => 'i_will_not_fear'})
+      assert @collection.index_information['i_will_not_fear']
+      @collection.drop_index([['a', Mongo::DESCENDING]])
+      assert_nil @collection.index_information['i_will_not_fear']
+    end
+  
+    should "drops an composite index" do
+      @collection.create_index([['a', Mongo::DESCENDING], ['b', Mongo::ASCENDING]])
+      assert @collection.index_information['a_-1_b_1']
+      @collection.drop_index([['a', Mongo::DESCENDING], ['b', Mongo::ASCENDING]])
+      assert_nil @collection.index_information['a_-1_b_1']
+    end
+    
+    should "drops an index with symbols" do
+      @collection.create_index([['a', Mongo::DESCENDING], [:b, Mongo::ASCENDING]])
+      assert @collection.index_information['a_-1_b_1']
+      @collection.drop_index([['a', Mongo::DESCENDING], [:b, Mongo::ASCENDING]])
+      assert_nil @collection.index_information['a_-1_b_1']
+    end
+  end
 
   context "Creating indexes " do
     setup do