added custom exception for illegal object ids

README.rdoc

@@ -329,7 +329,7 @@ See HISTORY.
 
 = Credits
 
-See CREDITS
+See CREDITS.
 
 = License
 

lib/mongo/errors.rb

@@ -30,6 +30,9 @@ module Mongo
   # Raised when given a string is not valid utf-8 (Ruby 1.8 only).
   class InvalidStringEncoding < MongoRubyError; end
 
+  # Raised when attempting to initialize an invalid ObjectID.
+  class InvalidObjectID < MongoRubyError; end
+
   # Raised on failures in connection to the database server.
   class ConnectionError < MongoRubyError; end
 

lib/mongo/types/objectid.rb

@@ -70,7 +70,7 @@ module Mongo
     # Given a string representation of an ObjectID, return a new ObjectID
     # with that value.
     def self.from_string(str)
-      raise "illegal ObjectID format" unless legal?(str)
+      raise InvalidObjectID, "illegal ObjectID format" unless legal?(str)
       data = []
       12.times do |i|
         data[i] = str[i * 2, 2].to_i(16)
@@ -83,7 +83,7 @@ module Mongo
     # removed. If you are not sure that you need this method you should be
     # using the regular from_string.
     def self.from_string_legacy(str)
-      raise "illegal ObjectID format" unless legal?(str)
+      raise InvalidObjectID, "illegal ObjectID format" unless legal?(str)
       data = []
       BYTE_ORDER.each_with_index { |string_position, data_index|
         data[data_index] = str[string_position * 2, 2].to_i(16)

test/test_objectid.rb

@@ -79,6 +79,12 @@ class ObjectIDTest < Test::Unit::TestCase
     assert_equal @o.to_s, o2.to_s
   end
 
+  def test_illegal_from_string
+    assert_raise InvalidObjectID do 
+      ObjectID.from_string("")
+    end
+  end
+
   def test_from_string_legacy
     hex_str = @o.to_s_legacy
     o2 = ObjectID.from_string_legacy(hex_str)
@@ -87,6 +93,12 @@ class ObjectIDTest < Test::Unit::TestCase
     assert_equal @o.to_s, o2.to_s
   end
 
+  def test_illegal_from_string_legacy
+    assert_raise InvalidObjectID do 
+      ObjectID.from_string_legacy("")
+    end
+  end
+
   def test_legal
     assert !ObjectID.legal?(nil)
     assert !ObjectID.legal?("fred")