Extract wrapped exception class creation

The wrapped exception classes are not created until ThriftClient.new
is called with the correct client class. This makes it difficult to
write code like `rescue MyThrift::Client::TransportException` because
the exception class may not exist yet.

Callers may now use ThriftClient.create_wrapped_exception_classes to
ensure the desired classes have been created.

lib/thrift_client/abstract_thrift_client.rb

@@ -35,6 +35,17 @@ class AbstractThriftClient
 
   attr_reader :last_client, :client, :client_class, :current_server, :server_list, :options, :client_methods
 
+  def self.create_wrapped_exception_classes(client_class, wrapped_exception_classes = DEFAULT_WRAPPED_ERRORS)
+    wrapped_exception_classes.map do |exception_klass|
+      name = exception_klass.to_s.split('::').last
+      begin
+        client_class.const_get(name)
+      rescue NameError
+        client_class.const_set(name, Class.new(exception_klass))
+      end
+    end
+  end
+
   def initialize(client_class, servers, options = {})
     @options = DEFAULTS.merge(options)
     @options[:server_retry_period] ||= 0
@@ -55,14 +66,7 @@ class AbstractThriftClient
       end
     end
     @request_count = 0
-    @options[:wrapped_exception_classes].each do |exception_klass|
-      name = exception_klass.to_s.split('::').last
-      begin
-        @client_class.const_get(name)
-      rescue NameError
-        @client_class.const_set(name, Class.new(exception_klass))
-      end
-    end
+    self.class.create_wrapped_exception_classes(@client_class, @options[:wrapped_exception_classes])
   end
 
   # Adds a callback that will be invoked at a certain time. The valid callback types are:

test/thrift_client_test.rb

@@ -26,6 +26,13 @@ class ThriftClientTest < Test::Unit::TestCase
     assert_equal "<ThriftClient(Greeter::Client) @current_server=127.0.0.1:1463>", client.inspect
   end
 
+  def test_create_wrapped_exception_classes
+    client = Module.new
+    ThriftClient.create_wrapped_exception_classes(client, [Thrift::TransportException])
+    assert client.const_defined?(:TransportException)
+    assert client.const_get(:TransportException).new.is_a?(Thrift::TransportException)
+  end
+
   def test_live_server
     assert_nothing_raised do
       ThriftClient.new(Greeter::Client, @servers.last, @options).greeting("someone")