Change the JUnit formatter to use events instead of callbacks.

Also use new style formatter initializer in the JUnit formatter.
Let the runtime handle that not all formatters write to a stream or
file.

features/docs/formatters/junit_formatter.feature

@@ -1,4 +1,3 @@
-@spawn
 Feature: JUnit output formatter
   In order for developers to create test reports with ant
   Cucumber should be able to output JUnit xml files
@@ -60,6 +59,7 @@ Feature: JUnit output formatter
             | is undefined |
       """
 
+  @spawn
   Scenario: one feature, one passing scenario, one failing scenario
     When I run `cucumber --format junit --out tmp/ features/one_passing_one_failing.feature`
     Then it should fail with:
@@ -101,6 +101,7 @@ Feature: JUnit output formatter
 
       """
 
+  @spawn
   Scenario: one feature in a subdirectory, one passing scenario, one failing scenario
     When I run `cucumber --format junit --out tmp/ features/some_subdirectory/one_passing_one_failing.feature --require features`
     Then it should fail with:
@@ -245,6 +246,7 @@ can't convert .* into String \(TypeError\)
 You *must* specify --out DIR for the junit formatter
       """
 
+  @spawn
   Scenario: strict mode, one feature, one scenario outline, four examples: one passing, one failing, one pending, one undefined
     When I run `cucumber --strict --format junit --out tmp/ features/scenario_outline.feature`
     Then it should fail with:
@@ -326,6 +328,7 @@ You *must* specify --out DIR for the junit formatter
 
       """ 
 
+  @spawn
   Scenario: strict mode with --expand option, one feature, one scenario outline, four examples: one passing, one failing, one pending, one undefined
     When I run `cucumber --strict --expand --format junit --out tmp/ features/scenario_outline.feature`
     Then it should fail with exactly:

lib/cucumber/formatter/junit.rb

@@ -1,4 +1,5 @@
 require 'builder'
+require 'cucumber/formatter/backtrace_filter'
 require 'cucumber/formatter/io'
 require 'cucumber/formatter/interceptor'
 require 'fileutils'
@@ -16,12 +17,17 @@ def initialize(feature_file)
         end
       end
 
-      def initialize(_runtime, io, options)
-        @reportdir = ensure_dir(io, "junit")
-        @options = options
+      def initialize(config)
+        config.on_event :before_test_case, &method(:on_before_test_case)
+        config.on_event :after_test_case, &method(:on_after_test_case)
+        config.on_event :after_test_step, &method(:on_after_test_step)
+        config.on_event :finished_testing, &method(:on_finished_testing)
+        @reportdir = ensure_dir(config.out_stream, "junit")
+        @config = config
       end
 
-      def before_test_case(test_case)
+      def on_before_test_case(event)
+        test_case = event.test_case
         unless same_feature_as_previous_test_case?(test_case.feature)
           end_feature if @current_feature
           start_feature(test_case.feature)
@@ -33,13 +39,15 @@ def before_test_case(test_case)
         @interceptederr = Interceptor::Pipe.wrap(:stderr)
       end
 
-      def after_test_step(test_step, result)
+      def on_after_test_step(event)
         return if @failing_step_source
 
-        @failing_step_source = test_step.source.last unless result.ok?(@options[:strict])
+        @failing_step_source = event.test_step.source.last unless event.result.ok?(@config.strict?)
       end
 
-      def after_test_case(test_case, result)
+      def on_after_test_case(event)
+        test_case = event.test_case
+        result = event.result.with_filtered_backtrace(Cucumber::Formatter::BacktraceFilter)
         test_case_name = NameBuilder.new(test_case)
         scenario = test_case_name.scenario_name
         scenario_designation = "#{scenario}#{test_case_name.name_suffix}"
@@ -50,7 +58,7 @@ def after_test_case(test_case, result)
         Interceptor::Pipe.unwrap! :stderr
       end
 
-      def done
+      def on_finished_testing(event)
         end_feature if @current_feature
       end
 
@@ -86,7 +94,7 @@ def end_feature
 
       def create_output_string(test_case, scenario, result, row_name)
         output = "#{test_case.keyword}: #{scenario}\n\n"
-        return output if result.ok?(@options[:strict])
+        return output if result.ok?(@config.strict?)
         if test_case.keyword == "Scenario"
           output += "#{@failing_step_source.keyword}" unless hook?(@failing_step_source)
           output += "#{@failing_step_source.name}\n"
@@ -107,7 +115,7 @@ def build_testcase(result, scenario_designation, output)
         name = scenario_designation
 
         @builder.testcase(:classname => classname, :name => name, :time => "%.6f" % duration) do
-          if !result.passed? && result.ok?(@options[:strict])
+          if !result.passed? && result.ok?(@config.strict?)
             @builder.skipped
             @skipped += 1
           elsif !result.passed?

lib/cucumber/runtime.rb

@@ -195,8 +195,8 @@ def formatters
 
     def create_formatter(factory, path_or_io, options)
       if !legacy_formatter?(factory)
-        out_stream = Cucumber::Formatter::Io.ensure_io(path_or_io)
-        return factory.new(@configuration.with_options(out_stream: out_stream))
+        return factory.new(@configuration) if path_or_io.nil?
+        return factory.new(@configuration.with_options(out_stream: path_or_io))
       end
       results = Formatter::LegacyApi::Results.new
       runtime_facade = Formatter::LegacyApi::RuntimeFacade.new(results, @support_code, @configuration)

spec/cucumber/formatter/junit_spec.rb

@@ -22,7 +22,7 @@ def write_file(feature_filename, data)
       context "With no options" do
         before(:each) do
           allow(File).to receive(:directory?) { true }
-          @formatter = TestDoubleJunitFormatter.new(runtime, '', {})
+          @formatter = TestDoubleJunitFormatter.new(actual_runtime.configuration.with_options(out_stream: ''))
         end
 
         after(:each) do
@@ -200,7 +200,7 @@ def after_step(step)
         let(:runtime)   { Runtime.new({:expand => true}) }
         before(:each) do
           allow(File).to receive(:directory?) { true }
-          @formatter = TestDoubleJunitFormatter.new(runtime, '', {:expand => true})
+          @formatter = TestDoubleJunitFormatter.new(actual_runtime.configuration.with_options(out_stream: '', :expand => true))
         end
 
         after(:each) do