Make Deprecations.set_logger! accept logger object

CHANGELOG.md

@@ -1,3 +1,9 @@
+# v0.3.2 2017-08-31
+
+### Added
+
+* Accept an existing logger object in `Dry::Core::Deprecations.set_logger!` (flash-gordon)
+
 # v0.3.1 2017-05-27
 
 ### Added

lib/dry/core/deprecations.rb

@@ -86,11 +86,24 @@ def logger(output = nil)
 
         # Sets a custom logger. This is a global setting.
         #
-        # @option [IO] output output stream for messages
+        # @overload set_logger!(output)
+        #   @param [IO] output Stream for messages
+        #
+        # @overload set_logger!
+        #   Stream messages to stdout
+        #
+        # @overload set_logger!(logger)
+        #   @param [#warn] logger
+        #
+        # @api public
         def set_logger!(output = nil)
-          @logger = Logger.new(output || $stdout)
-          @logger.formatter = proc { |_severity, _datetime, _progname, msg| "#{msg}\n" }
-          @logger
+          if output.respond_to?(:warn)
+            @logger = output
+          else
+            @logger = Logger.new(output || $stdout).tap do |logger|
+              logger.formatter = proc { |_, _, _, msg| "#{ msg }\n" }
+            end
+          end
         end
 
         def [](tag)

spec/dry/core/deprecations_spec.rb

@@ -137,4 +137,27 @@ def logging(msg)
       end
     end
   end
+
+  describe '.set_logger!' do
+    let(:logger) do
+      Class.new {
+        attr_reader :messages
+
+        def initialize
+          @messages = []
+        end
+
+        def warn(message)
+          messages << message
+        end
+      }.new
+    end
+
+    it 'accepts preconfigured logger' do
+      Dry::Core::Deprecations.set_logger!(logger)
+      Dry::Core::Deprecations.warn("Don't!")
+
+      expect(logger.messages).to eql(%w([deprecated]\ Don't!))
+    end
+  end
 end