Implement —rerun-failures CLI flag.

Author: myronmarston

lib/rspec/core/configuration.rb

@@ -224,6 +224,11 @@ def exclude_pattern=(value)
       # (default: `false`).
       add_setting :run_all_when_everything_filtered
 
+      # @macro add_setting
+      # Run only the examples that failed on the last run.
+      # (default: `false`).
+      add_setting :rerun_failures
+
       # @macro add_setting
       # Color to use to indicate success.
       # @param color [Symbol] defaults to `:green` but can be set to one of the
@@ -800,7 +805,14 @@ def files_or_directories_to_run=(*files)
       # The spec files RSpec will run.
       # @return [Array] specified files about to run
       def files_to_run
-        @files_to_run ||= get_files_to_run(@files_or_directories_to_run)
+        @files_to_run ||= begin
+          if rerun_failures?
+            failures = LastRunPersister.for_current_project.failures_from_last_run
+            self.files_or_directories_to_run = failures
+          end
+
+          get_files_to_run(@files_or_directories_to_run)
+        end
       end
 
       # Creates a method that delegates to `example` including the submitted

lib/rspec/core/configuration_options.rb

@@ -86,7 +86,7 @@ def order(keys)
         # These must be set before `requires` to support checking
         # `config.files_to_run` from within `spec_helper.rb` when a
         # `-rspec_helper` option is used.
-        :files_or_directories_to_run, :pattern, :exclude_pattern,
+        :files_or_directories_to_run, :pattern, :exclude_pattern, :rerun_failures,
 
         # Necessary so that the `--seed` option is applied before requires,
         # in case required files do something with the provided seed.

lib/rspec/core/option_parser.rb

@@ -156,6 +156,10 @@ def parser(options)
 
 FILTERING
 
+        parser.on('--rerun-failures', "Run just the examples that failed on the last run.") do
+          options[:rerun_failures] = true
+        end
+
         parser.on('-P', '--pattern PATTERN', 'Load files matching pattern (default: "spec/**/*_spec.rb").') do |o|
           options[:pattern] = o
         end

lib/rspec/core/reporter.rb

@@ -161,6 +161,7 @@ def finish
     def stop
       @duration = (RSpec::Core::Time.now - @start).to_f if @start
       notify :stop, Notifications::ExamplesNotification.new(self)
+      record_failures
     end
 
     # @private
@@ -181,6 +182,11 @@ def mute_profile_output?
     def seed_used?
       @configuration.seed && @configuration.seed_used?
     end
+
+    def record_failures
+      ids = @failed_examples.map(&:id)
+      LastRunPersister.for_current_project.persist_failures(ids)
+    end
   end
 
   # @private

spec/integration/filtering_spec.rb

@@ -65,6 +65,33 @@ def run_rerun_command_for_failing_spec
     end
   end
 
+  context "using --rerun-failures" do
+    it 'reruns the examples that failed on the last run' do
+      write_file_formatted 'spec/string_spec.rb', """
+        RSpec.describe 'Strings' do
+          specify { expect('a').to eq('a') }
+          specify { expect('a').to eq('b') } # failure
+          specify { expect('c').to eq('c') }
+          specify { expect('c').to eq('b') } # failure
+        end
+      """
+
+      write_file_formatted 'spec/array_spec.rb', """
+        RSpec.describe 'Arrays' do
+          specify { expect([1, 2]).to include(1) }
+          specify { expect([1, 2]).to include(3) } # failure
+          specify { expect([1, 2]).to include(2) }
+        end
+      """
+
+      run_command ""
+      expect(last_cmd_stdout).to match(/7 examples, 3 failures/)
+
+      run_command "--rerun-failures"
+      expect(last_cmd_stdout).to match(/3 examples, 3 failures/)
+    end
+  end
+
   context "passing a line-number filter" do
     it "trumps exclusions, except for :if/:unless (which are absolute exclusions)" do
       write_file_formatted 'spec/a_spec.rb', """

spec/rspec/core/configuration_options_spec.rb

@@ -90,6 +90,13 @@
       opts.configure(config)
     end
 
+    it "sets `rerun_failures` before `requires` so users can check `files_to_run` in a spec_helper loaded by `--require`" do
+      opts = config_options_object(*%w[--require spec_helper --rerun-failures])
+      expect(config).to receive(:force).with(:rerun_failures => true).ordered
+      expect(config).to receive(:requires=).ordered
+      opts.configure(config)
+    end
+
     it "sets default_path before `files_or_directories_to_run` since it relies on it" do
       opts = config_options_object(*%w[--default-path spec])
       expect(config).to receive(:force).with(:default_path => 'spec').ordered

spec/rspec/core/configuration_spec.rb

@@ -87,6 +87,40 @@ module RSpec::Core
       end
     end
 
+    describe "#rerun_failures=" do
+      context "when set to true" do
+        it 'assigns what to run from the previously persisted failures' do
+          failures = %w[ ./spec_1.rb[1:1] ]
+          persister = instance_double(LastRunPersister, :failures_from_last_run => failures)
+          allow(LastRunPersister).to receive(:for_current_project) { persister }
+
+          config.rerun_failures = true
+
+          expect(config.files_to_run).to contain_exactly("./spec_1.rb")
+          expect(inclusion_filter).to eq(:ids => { "./spec_1.rb" => ["1:1"] })
+        end
+
+        it 'indicates it has been set' do
+          expect {
+            config.rerun_failures = true
+          }.to change { config.rerun_failures? }.from(a_falsey_value).to(true)
+        end
+      end
+
+      context "when set to false" do
+        it 'does nothing' do
+          expect {
+            config.rerun_failures = false
+          }.not_to change { config.files_to_run }
+        end
+
+        it 'indicates it has been set to false' do
+          config.rerun_failures = false
+          expect(config.rerun_failures?).to be false
+        end
+      end
+    end
+
     describe "#requires=" do
       def absolute_path_to(dir)
         File.expand_path("../../../../#{dir}", __FILE__)

spec/rspec/core/reporter_spec.rb

@@ -33,6 +33,24 @@ module RSpec::Core
 
         reporter.finish
       end
+
+      def example_with_id(id)
+        new_example.tap do |ex|
+          allow(ex).to receive_messages(:id => id)
+        end
+      end
+
+      it 'records the failed examples in order to support the `--rerun-failures` flag' do
+        persister = instance_spy(LastRunPersister)
+        allow(LastRunPersister).to receive(:for_current_project) { persister }
+
+        reporter.example_failed(example_with_id("id_1"))
+        reporter.example_failed(example_with_id("id_2"))
+
+        reporter.finish
+
+        expect(persister).to have_received(:persist_failures).with(%w[ id_1 id_2 ])
+      end
     end
 
     describe 'start' do