Checking response on buildinfo command.

lib/mongo/connection.rb

@@ -122,7 +122,7 @@ module Mongo
 
     # Return the build information for the current connection.
     def server_info
-      db("admin").db_command(:buildinfo => 1)
+      db("admin").command({:buildinfo => 1}, {:admin => true, :check_response => true})
     end
 
     # Returns the build version of the current server, using

lib/mongo/db.rb

@@ -501,6 +501,35 @@ module Mongo
       cursor = Cursor.new(Collection.new(self, SYSTEM_COMMAND_COLLECTION), :admin => use_admin_db, :limit => -1, :selector => selector)
       cursor.next_object
     end
+    
+    # Sends a command to the database.
+    #
+    # :selector (required) :: An OrderedHash, or a standard Hash with just one
+    # key, specifying the command to be performed.
+    #
+    # :admin (optional) :: If true, the command will be executed on the admin
+    # collection.
+    #
+    # :check_response (optional) :: If true, will raise an exception if the
+    # command fails.
+    #
+    # Note: DB commands must start with the "command" key. For this reason,
+    # any selector containing more than one key must be an OrderedHash.
+    def command(selector, admin=false, check_response=false)
+      raise MongoArgumentError, "command must be given a selector" unless selector.is_a?(Hash) && !selector.empty?
+      if selector.class.eql?(Hash) && selector.keys.length > 1 
+        raise MongoArgumentError, "DB#command requires an OrderedHash when hash contains multiple keys"
+      end
+
+      result = Cursor.new(system_command_collection, :admin => admin, 
+        :limit => -1, :selector => selector).next_object
+
+      if check_response && !ok?(result)
+        raise OperationFailure, "Database command '#{selector.keys.first}' failed."
+      else
+        result
+      end
+    end
 
     def _synchronize &block
       @semaphore.synchronize &block
@@ -541,5 +570,9 @@ module Mongo
     def hash_password(username, plaintext)
       Digest::MD5.hexdigest("#{username}:mongo:#{plaintext}")
     end
+
+    def system_command_collection
+      Collection.new(self, SYSTEM_COMMAND_COLLECTION)
+    end
   end
 end

lib/mongo/errors.rb

@@ -18,6 +18,9 @@ module Mongo
   # Generic Mongo Ruby Driver exception class.
   class MongoRubyError < StandardError; end
 
+  # Raised when MongoDB itself has returned an error.
+  class MongoDBError < RuntimeError; end
+
   # Raised when configuration options cause connections, queries, etc., to fail.
   class ConfigurationError < MongoRubyError; end
 
@@ -25,10 +28,10 @@ module Mongo
   class MongoArgumentError < MongoRubyError; end
 
   # Raised when a database operation fails.
-  class OperationFailure < RuntimeError; end
+  class OperationFailure < MongoDBError; end
 
   # Raised when a client attempts to perform an invalid operation.
-  class InvalidOperation < RuntimeError; end
+  class InvalidOperation < MongoDBError; end
 
   # Raised when an invalid name is used.
   class InvalidName < RuntimeError; end

test/test_db.rb

@@ -189,6 +189,13 @@ class DBTest < Test::Unit::TestCase
     assert_nil @@db.previous_error
   end
 
+  def test_check_command_response
+    command = {:forceerror => 1}
+    assert_raise OperationFailure do 
+      @@db.command(command, false, true)
+    end
+  end
+
   def test_last_status
     @@db['test'].remove
     @@db['test'].save("i" => 1)

test/unit/db_test.rb

@@ -0,0 +1,52 @@
+require 'test/test_helper'
+
+class DBTest < Test::Unit::TestCase
+
+  class MockDB < DB
+
+    def connect_to_master
+      true
+    end
+  end
+
+  context "DB commands" do 
+    setup do 
+      @db = MockDB.new("testing", ['localhost', 27017])
+      @collection = mock()
+      @db.stubs(:system_command_collection).returns(@collection)
+    end
+
+    should "raise an error if given a hash with more than one key" do
+      assert_raise MongoArgumentError do 
+        @db.command(:buildinfo => 1, :somekey => 1)
+      end
+    end
+
+    should "raise an error if the selector is omitted" do 
+      assert_raise MongoArgumentError do 
+        @db.command({}, true)
+      end
+    end
+
+    should "create the proper cursor" do 
+      @cursor = mock(:next_object => {"ok" => 1})
+      Cursor.expects(:new).with(@collection, :admin => true,
+        :limit => -1, :selector => {:buildinfo => 1}).returns(@cursor)
+      command = {:buildinfo => 1}
+      @db.command(command, true)
+    end
+
+    should "raise an error when the command fails" do 
+      @cursor = mock(:next_object => {"ok" => 0})
+      Cursor.expects(:new).with(@collection, :admin => true,
+        :limit => -1, :selector => {:buildinfo => 1}).returns(@cursor)
+      assert_raise OperationFailure do 
+        command = {:buildinfo => 1}
+        @db.command(command, true, true)
+      end
+    end
+  end
+
+end
+
+