send file when file

lib/rspec/core/configuration.rb

@@ -105,6 +105,9 @@ def self.add_setting(name, opts={})
       # @macro add_setting
       # Default: `$stderr`.
       add_setting :deprecation_stream
+      def deprecation_stream=(filename_or_io)
+        @deprecation_stream = file_or_io_from(filename_or_io)
+      end
 
       # @macro add_setting
       # Clean up and exit after the first failure (default: `false`).
@@ -1061,6 +1064,10 @@ def underscore(camel_cased_word)
         word
       end
 
+      def file_or_io_from(output)
+        String === output ? file_at(output) : output
+      end
+
       def file_at(path)
         FileUtils.mkdir_p(File.dirname(path))
         File.new(path, 'w')

spec/rspec/core/configuration_spec.rb

@@ -26,6 +26,11 @@ module RSpec::Core
         config.deprecation_stream = io
         expect(config.deprecation_stream).to eq io
       end
+
+      it 'will load a file from a filename' do
+        config.deprecation_stream = 'string.rb'
+        expect(config.deprecation_stream).to be_a File
+      end
     end
 
     describe "#setup_load_path_and_require" do