support progress bar formatters

lib/parallel_tests/cli.rb

@@ -212,6 +212,7 @@ def parse_options!(argv)
         opts.on("--serialize-stdout", "Serialize stdout output, nothing will be written until everything is done") { options[:serialize_stdout] = true }
         opts.on("--prefix-output-with-test-env-number", "Prefixes test env number to the output when not using --serialize-stdout") { options[:prefix_output_with_test_env_number] = true }
         opts.on("--combine-stderr", "Combine stderr into stdout, useful in conjunction with --serialize-stdout") { options[:combine_stderr] = true }
+        opts.on("--progress-bar-compatible", "Serialize stdout output, but write immediately and rewrite on the fly") { options[:progress_bar_compatible] = true; options[:combine_stderr] = false }
         opts.on("--non-parallel", "execute same commands but do not in parallel, needs --exec") { options[:non_parallel] = true }
         opts.on("--no-symlinks", "Do not traverse symbolic links to find test files") { options[:symlinks] = false }
         opts.on('--ignore-tags [PATTERN]', 'When counting steps ignore scenarios with tags that match this pattern')  { |arg| options[:ignore_tag_pattern] = arg }

lib/parallel_tests/output_rewriter.rb

@@ -0,0 +1,24 @@
+require 'parallel_tests'
+
+module ParallelTests
+  class OutputRewriter
+    CURSOR_UP_CHARACTER = "\033[A"
+
+    $output_rewrite_mutex = Mutex.new
+    $output_by_group = []
+
+    def self.rewrite(new_group_output:, group_index:)
+      $output_rewrite_mutex.synchronize do
+        number_of_lines_to_overwrite = $output_by_group.sum { |s| s.to_s.count("\n") }
+
+        $output_by_group[group_index] = new_group_output
+
+        result = CURSOR_UP_CHARACTER * number_of_lines_to_overwrite
+        $output_by_group.each { |group_output| result += group_output.to_s }
+
+        $stdout.print result
+        $stdout.flush
+      end
+    end
+  end
+end

lib/parallel_tests/test/runner.rb

@@ -1,4 +1,5 @@
 require 'parallel_tests'
+require 'parallel_tests/output_rewriter'
 
 module ParallelTests
   module Test
@@ -158,7 +159,10 @@ def capture_output(out, env, options={})
                 read = read.force_encoding(Encoding.default_internal)
               end
               result << read
-              unless options[:serialize_stdout]
+
+              if options[:progress_bar_compatible]
+                ParallelTests::OutputRewriter.rewrite(new_group_output: result, group_index: env['TEST_ENV_NUMBER'].to_i)
+              elsif !options[:serialize_stdout]
                 message = read
                 message = "[TEST GROUP #{env['TEST_ENV_NUMBER']}] #{message}" if options[:prefix_output_with_test_env_number]
                 $stdout.print message