Add bisect formatter and server.

lib/rspec/core/bisect/server.rb

@@ -0,0 +1,46 @@
+require 'drb/drb'
+
+module RSpec
+  module Core
+    # @private
+    module Bisect
+      # @private
+      # A DRb server that receives run results from a separate RSpec process
+      # started by the bisect process.
+      class Server
+        def self.run
+          server = new
+          server.start
+          yield server
+        ensure
+          server.stop
+        end
+
+        def capture_run_results(abort_after_example_id=nil)
+          self.abort_after_example_id = abort_after_example_id
+          yield
+          latest_run_results
+        end
+
+        def start
+          # We pass `nil` as the first arg to allow it to pick a DRb port.
+          @drb = DRb.start_service(nil, self)
+        end
+
+        def stop
+          @drb.stop_service
+        end
+
+        def drb_port
+          @drb_port ||= Integer(@drb.uri[/\d+$/])
+        end
+
+        # Fetched via DRb by the BisectFormatter to determine when to abort.
+        attr_accessor :abort_after_example_id
+
+        # Set via DRb by the BisectFormatter with the results of the run.
+        attr_accessor :latest_run_results
+      end
+    end
+  end
+end

lib/rspec/core/formatters.rb

@@ -71,6 +71,7 @@ module RSpec::Core::Formatters
   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
@@ -186,6 +187,8 @@ def built_in_formatter(key)
         ProgressFormatter
       when 'j', 'json'
         JsonFormatter
+      when 'bisect'
+        BisectFormatter
       end
     end
 

lib/rspec/core/formatters/bisect_formatter.rb

@@ -0,0 +1,66 @@
+require 'drb/drb'
+
+module RSpec
+  module Core
+    module Formatters
+      # Used by `--bisect`. When it shells out and runs a portion of the suite, it uses
+      # this formatter as a means to have the status reported back to it, via DRb.
+      #
+      # Note that since DRb calls carry considerable overhead compared to normal
+      # method calls, we try to minimize the number of DRb calls for perf reasons,
+      # opting to communicate only at the start and the end of the run, rather than
+      # after each example.
+      # @private
+      class BisectFormatter
+        Formatters.register self, :start, :start_dump, :example_started,
+                            :example_failed, :example_passed, :example_pending
+
+        def initialize(_output)
+          port                = RSpec.configuration.drb_port
+          drb_uri             = "druby://127.0.0.1:#{port}"
+          @all_example_ids    = []
+          @failed_example_ids = []
+          @bisect_server      = DRbObject.new_with_uri(drb_uri)
+          @abort_after_id     = nil
+        end
+
+        def start(_notification)
+          @abort_after_id = @bisect_server.abort_after_example_id
+        end
+
+        def example_started(notification)
+          @all_example_ids << notification.example.id
+        end
+
+        def example_failed(notification)
+          @failed_example_ids << notification.example.id
+          example_finished(notification)
+        end
+
+        def example_passed(notification)
+          example_finished(notification)
+        end
+
+        def example_pending(notification)
+          example_finished(notification)
+        end
+
+        def start_dump(_notification)
+          @bisect_server.latest_run_results = RunResults.new(
+            @all_example_ids, @failed_example_ids
+          )
+        end
+
+        RunResults = Struct.new(:all_example_ids_in_execution_order,
+                                :failed_example_ids)
+
+      private
+
+        def example_finished(notification)
+          return unless notification.example.id == @abort_after_id
+          RSpec.world.wants_to_quit = true
+        end
+      end
+    end
+  end
+end

spec/rspec/core/bisect/server_spec.rb

@@ -0,0 +1,90 @@
+require 'rspec/core/bisect/server'
+require 'support/formatter_support'
+
+module RSpec::Core
+  RSpec.describe Bisect::Server do
+    RSpec::Matchers.define :have_running_server do
+      match do |drb|
+        begin
+          drb.current_server.alive?
+        rescue DRb::DRbServerNotFound
+          false
+        end
+      end
+    end
+
+    it 'always stops the server, even if an error occurs while yielding' do
+      expect(DRb).not_to have_running_server
+
+      expect {
+        Bisect::Server.run do
+          expect(DRb).to have_running_server
+          raise "boom"
+        end
+      }.to raise_error("boom")
+
+      expect(DRb).not_to have_running_server
+    end
+
+    context "when used in combination with the BisectFormatter", :slow do
+      include FormatterSupport
+
+      attr_reader :server
+
+      around do |ex|
+        Bisect::Server.run do |the_server|
+          @server = the_server
+          ex.run
+        end
+      end
+
+      def run_formatter_specs
+        RSpec.configuration.drb_port = server.drb_port
+        run_example_specs_with_formatter("bisect")
+      end
+
+      it 'receives suite results' do
+        results = server.capture_run_results do
+          run_formatter_specs
+        end
+
+        expect(results).to have_attributes(
+          :all_example_ids_in_execution_order => %w[
+            ./spec/rspec/core/resources/formatter_specs.rb[1:1]
+            ./spec/rspec/core/resources/formatter_specs.rb[2:1:1]
+            ./spec/rspec/core/resources/formatter_specs.rb[2:2:1]
+            ./spec/rspec/core/resources/formatter_specs.rb[3:1]
+            ./spec/rspec/core/resources/formatter_specs.rb[4:1]
+            ./spec/rspec/core/resources/formatter_specs.rb[5:1]
+            ./spec/rspec/core/resources/formatter_specs.rb[5:2]
+          ],
+          :failed_example_ids => %w[
+            ./spec/rspec/core/resources/formatter_specs.rb[2:2:1]
+            ./spec/rspec/core/resources/formatter_specs.rb[4:1]
+            ./spec/rspec/core/resources/formatter_specs.rb[5:1]
+            ./spec/rspec/core/resources/formatter_specs.rb[5:2]
+          ]
+        )
+      end
+
+      it 'can abort the run early (e.g. when it is not interested in later examples)' do
+        results = server.capture_run_results("./spec/rspec/core/resources/formatter_specs.rb[2:2:1]") do
+          run_formatter_specs
+        end
+
+        expect(results).to have_attributes(
+          :all_example_ids_in_execution_order => %w[
+            ./spec/rspec/core/resources/formatter_specs.rb[1:1]
+            ./spec/rspec/core/resources/formatter_specs.rb[2:1:1]
+            ./spec/rspec/core/resources/formatter_specs.rb[2:2:1]
+          ],
+          :failed_example_ids => %w[
+            ./spec/rspec/core/resources/formatter_specs.rb[2:2:1]
+          ]
+        )
+      end
+
+      # TODO: test aborting after pending vs failed vs passing example if we keep this feature.
+    end
+  end
+end