Add fallback formatter for #message

Changelog.md

@@ -47,6 +47,8 @@ Enhancements:
   `aggregate_failures` feature to allow multiple failures in an example
   and list them all, rather than aborting on the first failure. (Myron
   Marston, #1946)
+* When no formatter implements #message add a fallback to prevent those
+  messages being lost. (Jon Rowe, #1980)
 
 Bug Fixes:
 

lib/rspec/core/formatters.rb

@@ -66,12 +66,13 @@
 # @see RSpec::Core::Formatters::BaseTextFormatter
 # @see RSpec::Core::Reporter
 module RSpec::Core::Formatters
-  autoload :DocumentationFormatter, 'rspec/core/formatters/documentation_formatter'
-  autoload :HtmlFormatter,          'rspec/core/formatters/html_formatter'
-  autoload :ProgressFormatter,      'rspec/core/formatters/progress_formatter'
-  autoload :ProfileFormatter,       'rspec/core/formatters/profile_formatter'
-  autoload :JsonFormatter,          'rspec/core/formatters/json_formatter'
-  autoload :BisectFormatter,        'rspec/core/formatters/bisect_formatter'
+  autoload :DocumentationFormatter,   'rspec/core/formatters/documentation_formatter'
+  autoload :HtmlFormatter,            'rspec/core/formatters/html_formatter'
+  autoload :FallbackMessageFormatter, 'rspec/core/formatters/fallback_message_formatter'
+  autoload :ProgressFormatter,        'rspec/core/formatters/progress_formatter'
+  autoload :ProfileFormatter,         'rspec/core/formatters/profile_formatter'
+  autoload :JsonFormatter,            'rspec/core/formatters/json_formatter'
+  autoload :BisectFormatter,          'rspec/core/formatters/bisect_formatter'
 
   # Register the formatter class
   # @param formatter_class [Class] formatter class to register
@@ -121,6 +122,10 @@ def setup_default(output_stream, deprecation_stream)
         add DeprecationFormatter, deprecation_stream, output_stream
       end
 
+      unless existing_formatter_implements?(:message)
+        add FallbackMessageFormatter, output_stream
+      end
+
       return unless RSpec.configuration.profile_examples? && !existing_formatter_implements?(:dump_profile)
 
       add RSpec::Core::Formatters::ProfileFormatter, output_stream

lib/rspec/core/formatters/fallback_message_formatter.rb

@@ -0,0 +1,28 @@
+module RSpec
+  module Core
+    module Formatters
+      # @api private
+      # Formatter for providing message output as a fallback when no other
+      # profiler implements #message
+      class FallbackMessageFormatter
+        Formatters.register self, :message
+
+        def initialize(output)
+          @output = output
+        end
+
+        # @private
+        attr_reader :output
+
+        # @api public
+        #
+        # Used by the reporter to send messages to the output stream.
+        #
+        # @param notification [MessageNotification] containing message
+        def message(notification)
+          output.puts notification.message
+        end
+      end
+    end
+  end
+end

spec/rspec/core/formatters/fallback_message_formatter_spec.rb

@@ -0,0 +1,18 @@
+require 'rspec/core/reporter'
+require 'rspec/core/formatters/fallback_message_formatter'
+
+module RSpec::Core::Formatters
+  RSpec.describe FallbackMessageFormatter do
+    include FormatterSupport
+
+    describe "#message" do
+      it 'writes the message to the output' do
+        expect {
+          send_notification :message, message_notification('Custom Message')
+        }.to change { formatter_output.string }.
+          from(excluding 'Custom Message').
+          to(including 'Custom Message')
+      end
+    end
+  end
+end

spec/rspec/core/formatters_spec.rb

@@ -130,28 +130,55 @@ module RSpec::Core::Formatters
       end
     end
 
-    describe "#setup_default", "with profiling enabled" do
+    describe "#setup_default" do
       let(:setup_default) { loader.setup_default output, output }
 
-      before do
-        allow(RSpec.configuration).to receive(:profile_examples?) { true }
+      context "with a formatter that implements #message" do
+        it 'doesnt add a fallback formatter' do
+          allow(reporter).to receive(:registered_listeners).with(:message) { [:json] }
+          setup_default
+          expect(loader.formatters).to exclude(
+            an_instance_of ::RSpec::Core::Formatters::FallbackMessageFormatter
+          )
+        end
       end
 
-      context "without an existing profile formatter" do
-        it "will add the profile formatter" do
-          allow(reporter).to receive(:registered_listeners).with(:dump_profile) { [] }
-          setup_default
-          expect(loader.formatters.last).to be_a ::RSpec::Core::Formatters::ProfileFormatter
+      context "without a formatter that implements #message" do
+        it 'adds a fallback for message output' do
+          allow(reporter).to receive(:registered_listeners).with(:message) { [] }
+          expect {
+            setup_default
+          }.to change { loader.formatters }.
+            from( excluding an_instance_of ::RSpec::Core::Formatters::FallbackMessageFormatter ).
+            to( including an_instance_of ::RSpec::Core::Formatters::FallbackMessageFormatter )
         end
       end
 
-      context "when a formatter that implement #dump_profile is added" do
-        it "wont add the profile formatter" do
-          allow(reporter).to receive(:registered_listeners).with(:dump_profile) { [:json] }
-          setup_default
-          expect(
-            loader.formatters.map(&:class)
-          ).to_not include ::RSpec::Core::Formatters::ProfileFormatter
+      context "with profiling enabled" do
+        before do
+          allow(reporter).to receive(:registered_listeners).with(:message) { [:json] }
+          allow(RSpec.configuration).to receive(:profile_examples?) { true }
+        end
+
+        context "without an existing profile formatter" do
+          it "will add the profile formatter" do
+            allow(reporter).to receive(:registered_listeners).with(:dump_profile) { [] }
+            expect {
+              setup_default
+            }.to change { loader.formatters }.
+              from( excluding an_instance_of ::RSpec::Core::Formatters::ProfileFormatter ).
+              to( including an_instance_of ::RSpec::Core::Formatters::ProfileFormatter )
+          end
+        end
+
+        context "when a formatter that implement #dump_profile is added" do
+          it "wont add the profile formatter" do
+            allow(reporter).to receive(:registered_listeners).with(:dump_profile) { [:json] }
+            setup_default
+            expect(
+              loader.formatters.map(&:class)
+            ).to_not include ::RSpec::Core::Formatters::ProfileFormatter
+          end
         end
       end
     end

spec/support/matchers.rb

@@ -121,4 +121,5 @@ def failure_reason(example)
 
 RSpec::Matchers.define_negated_matcher :avoid_outputting, :output
 RSpec::Matchers.define_negated_matcher :exclude, :include
+RSpec::Matchers.define_negated_matcher :excluding, :include
 RSpec::Matchers.define_negated_matcher :avoid_changing,   :change