[Fix #7686] Add new JUnitFormatter

Fixes #7686.

This PR Adds new `JUnitFormatter` formatter based on rubocop-junit-formatter gem.
https://github.com/mikian/rubocop-junit-formatter

And this PR includes the following patch to implementation of `JUnitFormatter`.
mikian/rubocop-junit-formatter#11.

REXML gem has been bundled gem since Ruby 2.8.0-dev (Ruby 3.0), it is
added to depend on gemspec.

- https://bugs.ruby-lang.org/issues/16485
- ruby/ruby@c3ccf23

.rubocop.yml

@@ -95,6 +95,10 @@ Metrics/ModuleLength:
   Exclude:
     - 'spec/**/*.rb'
 
+RSpec/FilePath:
+  Exclude:
+    - spec/rubocop/formatter/junit_formatter_spec.rb
+
 RSpec/PredicateMatcher:
   EnforcedStyle: explicit
 

CHANGELOG.md

@@ -10,6 +10,7 @@
 * [#7659](https://github.com/rubocop-hq/rubocop/pull/7659): Layout/LineLength autocorrect now breaks up long lines with blocks. ([@maxh][])
 * [#7677](https://github.com/rubocop-hq/rubocop/pull/7677): Add a cop for `Hash#each_key` and `Hash#each_value`. ([@jemmaissroff][])
 * Add `BracesRequiredMethods` parameter to `Style/BlockDelimiters` to require braces for specific methods such as Sorbet's `sig`. ([@maxh][])
+* [#7686](https://github.com/rubocop-hq/rubocop/pull/7686): Add new `JUnitFormatter` formatter based on rubocop-junit-formatter gem. ([@koic][])
 
 ### Bug fixes
 

Gemfile

@@ -18,11 +18,6 @@ gem 'test-queue'
 gem 'yard', '~> 0.9'
 
 group :test do
-  # Workaround for crack 0.4.3 or lower.
-  # Depends on `rexml` until the release that includes
-  # the following changes:
-  # https://github.com/jnunemaker/crack/pull/62
-  gem 'rexml'
   gem 'safe_yaml', require: false
   gem 'webmock', require: false
 end

lib/rubocop.rb

@@ -588,6 +588,7 @@
 require_relative 'rubocop/formatter/fuubar_style_formatter'
 require_relative 'rubocop/formatter/html_formatter'
 require_relative 'rubocop/formatter/json_formatter'
+require_relative 'rubocop/formatter/junit_formatter'
 require_relative 'rubocop/formatter/offense_count_formatter'
 require_relative 'rubocop/formatter/progress_formatter'
 require_relative 'rubocop/formatter/quiet_formatter'

lib/rubocop/formatter/formatter_set.rb

@@ -17,6 +17,7 @@ class FormatterSet < Array
         '[fu]ubar'      => FuubarStyleFormatter,
         '[h]tml'        => HTMLFormatter,
         '[j]son'        => JSONFormatter,
+        '[ju]nit'       => JUnitFormatter,
         '[o]ffenses'    => OffenseCountFormatter,
         '[pa]cman'      => PacmanFormatter,
         '[p]rogress'    => ProgressFormatter,

lib/rubocop/formatter/junit_formatter.rb

@@ -0,0 +1,63 @@
+# frozen_string_literal: true
+
+require 'rexml/document'
+
+#
+# This code is based on https://github.com/mikian/rubocop-junit-formatter.
+#
+# Copyright (c) 2015 Mikko Kokkonen
+#
+# MIT License
+#
+# https://github.com/mikian/rubocop-junit-formatter/blob/master/LICENSE.txt
+#
+module RuboCop
+  module Formatter
+    # This formatter formats the report data in JUnit format.
+    class JUnitFormatter < BaseFormatter
+      def initialize(output, options = {})
+        super
+
+        @document = REXML::Document.new.tap do |document|
+          document << REXML::XMLDecl.new
+        end
+        testsuites = REXML::Element.new('testsuites', @document)
+        testsuite = REXML::Element.new('testsuite', testsuites)
+        @testsuite = testsuite.tap do |element|
+          element.add_attributes('name' => 'rubocop')
+        end
+      end
+
+      def file_finished(file, offenses)
+        offenses.group_by(&:cop_name).each do |cop_name, grouped_offenses|
+          REXML::Element.new('testcase', @testsuite).tap do |testcase|
+            testcase.attributes['classname'] = file.gsub(
+              /\.rb\Z/, ''
+            ).gsub("#{Dir.pwd}/", '').tr('/', '.')
+            testcase.attributes['name'] = cop_name
+
+            add_failure_to(testcase, grouped_offenses, cop_name)
+          end
+        end
+      end
+
+      def finished(_inspected_files)
+        @document.write(output, 2)
+      end
+
+      private
+
+      def add_failure_to(testcase, offenses, cop_name)
+        # One failure per offense. Zero failures is a passing test case,
+        # for most surefire/nUnit parsers.
+        offenses.each do |offense|
+          REXML::Element.new('failure', testcase).tap do |failure|
+            failure.attributes['type'] = cop_name
+            failure.attributes['message'] = offense.message
+            failure.add_text(offense.location.to_s)
+          end
+        end
+      end
+    end
+  end
+end

manual/formatters.md

@@ -237,6 +237,37 @@ The JSON structure is like the following example:
 }
 ```
 
+### JUnit Style Formatter
+
+**Machine-parsable**
+
+The `junit` style formatter provides the JUnit formatting.
+This formatter is based on [rubocop-junit-formatter gem](https://github.com/mikian/rubocop-junit-formatter).
+
+```sh
+$ rubocop --format junit
+<?xml version='1.0'?>
+<testsuites>
+  <testsuite name='rubocop'>
+    <testcase classname='example' name='Style/FrozenStringLiteralComment'>
+      <failure type='Style/FrozenStringLiteralComment' message='Style/FrozenStringLiteralComment: Missing frozen string literal comment.'>
+        /tmp/src/example.rb:1:1
+      </failure>
+    </testcase>
+    <testcase classname='example' name='Naming/MethodName'>
+      <failure type='Naming/MethodName' message='Naming/MethodName: Use snake_case for method names.'>
+        /tmp/src/example.rb:1:5
+      </failure>
+    </testcase>
+    <testcase classname='example' name='Lint/DeprecatedClassMethods'>
+      <failure type='Lint/DeprecatedClassMethods' message='Lint/DeprecatedClassMethods: `File.exists?` is deprecated in favor of `File.exist?`.'>
+        /tmp/src/example.rb:2:8
+      </failure>
+    </testcase>
+  </testsuite>
+</testsuites>
+```
+
 ### Offense Count Formatter
 
 Sometimes when first applying RuboCop to a codebase, it's nice to be able to

rubocop.gemspec

@@ -37,6 +37,7 @@ Gem::Specification.new do |s|
   s.add_runtime_dependency('parallel', '~> 1.10')
   s.add_runtime_dependency('parser', '>= 2.7.0.1')
   s.add_runtime_dependency('rainbow', '>= 2.2.2', '< 4.0')
+  s.add_runtime_dependency('rexml')
   s.add_runtime_dependency('ruby-progressbar', '~> 1.7')
   s.add_runtime_dependency('unicode-display_width', '>= 1.4.0', '< 1.7')
 

spec/rubocop/formatter/junit_formatter_spec.rb

@@ -0,0 +1,55 @@
+# frozen_string_literal: true
+
+RSpec.describe RuboCop::Formatter::JUnitFormatter do
+  subject(:formatter) { described_class.new(output) }
+
+  let(:output) { StringIO.new }
+
+  describe '#file_finished' do
+    it 'displays parsable text' do
+      cop = RuboCop::Cop::Cop.new
+      source_buffer = Parser::Source::Buffer.new('test', 1)
+      source_buffer.source = %w[foo bar baz].join("\n")
+
+      cop.add_offense(
+        nil,
+        location: Parser::Source::Range.new(source_buffer, 0, 1),
+        message: 'message 1'
+      )
+      cop.add_offense(
+        nil,
+        location: Parser::Source::Range.new(source_buffer, 9, 10),
+        message: 'message 2'
+      )
+
+      formatter.file_finished('test_1', cop.offenses)
+      formatter.file_finished('test_2', cop.offenses)
+
+      formatter.finished(nil)
+
+      expect(output.string).to eq(<<~XML.chop)
+        <?xml version='1.0'?>
+        <testsuites>
+          <testsuite name='rubocop'>
+            <testcase classname='test_1' name='Cop/Cop'>
+              <failure type='Cop/Cop' message='message 1'>
+                test:1:1
+              </failure>
+              <failure type='Cop/Cop' message='message 2'>
+                test:3:2
+              </failure>
+            </testcase>
+            <testcase classname='test_2' name='Cop/Cop'>
+              <failure type='Cop/Cop' message='message 1'>
+                test:1:1
+              </failure>
+              <failure type='Cop/Cop' message='message 2'>
+                test:3:2
+              </failure>
+            </testcase>
+          </testsuite>
+        </testsuites>
+      XML
+    end
+  end
+end

spec/rubocop/options_spec.rb

@@ -77,6 +77,7 @@ def abs(path)
                                                  [fu]ubar
                                                  [h]tml
                                                  [j]son
+                                                 [ju]nit
                                                  [o]ffenses
                                                  [pa]cman
                                                  [p]rogress