Add :on_rails hook to rspec

Gemfile

@@ -9,6 +9,7 @@ group :development do
 end
 
 group :test do
+  gem 'rails', '~> 7.1.1'
   gem 'rspec', '~> 3.2'
   gem 'simplecov', '~> 0.21'
 end

Rakefile

@@ -1,10 +1,38 @@
 # frozen_string_literal: true
 
 require 'bundler/gem_tasks'
-require 'rubocop/rake_task'
-require 'rspec/core/rake_task'
 
-RSpec::Core::RakeTask.new(:spec)
-RuboCop::RakeTask.new
+task default: %i[rubocop spec]
 
-task default: %i[spec rubocop]
+desc 'Run RuboCop'
+task :rubocop do
+  require 'rubocop/rake_task'
+
+  RuboCop::RakeTask.new
+end
+
+desc 'Run tests'
+task :spec do
+  require 'rspec/core/rake_task'
+
+  RSpec::Core::RakeTask.new(:spec)
+end
+
+RAILS_DUMMY_DIR = 'tmp/test/dummy/'
+
+namespace :rails do
+  desc 'Generate dummy rails application'
+  task :generate_dummy_app, [:dir] do |_t, args|
+    dummy_app_dir = args.fetch(:dir, RAILS_DUMMY_DIR)
+    exit(0) if Dir.exist?(dummy_app_dir)
+
+    system(
+      "rails new #{dummy_app_dir} " \
+      '--skip-git --skip-asset-pipeline --skip-action-cable ' \
+      '--skip-action-mailer --skip-action-mailbox --skip-action-text ' \
+      '--skip-active-record --skip-active-job --skip-active-storage ' \
+      '--skip-javascript --skip-hotwire --skip-jbuilder ' \
+      '--skip-test --skip-system-test --skip-bootsnap ',
+    )
+  end
+end

spec/rspec_settings.rb

@@ -3,13 +3,20 @@
 require 'simplecov'
 SimpleCov.start do
   add_filter '/spec/'
+  add_filter %r{^/tmp/}
 end
 
 require 'uber_task'
 require 'colorize'
 
+require_relative 'support/rails_manager'
+
 RSpec.configure do |config|
   config.expect_with :rspec do |c|
     c.syntax = :expect
   end
+
+  config.around(:example, :on_rails) do |example|
+    RailsManager.new(config).on_rails { example.run }
+  end
 end

spec/support/rails_manager.rb

@@ -0,0 +1,47 @@
+# frozen_string_literal: true
+
+require 'rake'
+
+class RailsManager
+  APP_PATH = '../../tmp/test/dummy/'
+
+  attr_reader :config, :app_path
+
+  def initialize(config, app_path: APP_PATH)
+    @config = config
+    @app_path = app_path
+  end
+
+  def on_rails
+    load_rails!
+    yield
+    unload_rails!
+  end
+
+  private
+
+  def load_rails!
+    return if defined?(Rails)
+
+    if config.instance_variable_defined?(:@rails)
+      Object.const_set(:Rails, config.instance_variable_get(:@rails))
+      return
+    end
+
+    absolute_app_path = File.expand_path(app_path, __dir__)
+    system("rake rails:generate_dummy_app[#{absolute_app_path}]")
+
+    require File.expand_path(
+      File.join(absolute_app_path, '/config/environment.rb'),
+      __dir__,
+    )
+
+    ENV['RAILS_ROOT'] = absolute_app_path
+    config.instance_variable_set(:@rails, Object.const_get(:Rails))
+  end
+
+  def unload_rails!
+    ENV.delete('RAILS_ROOT')
+    Object.send(:remove_const, :Rails)
+  end
+end

spec/support_specs/rails_manager_spec.rb

@@ -0,0 +1,47 @@
+# frozen_string_literal: true
+
+require 'tmpdir'
+
+describe RailsManager do
+  let(:manager) { described_class.new(config, app_path: app_path) }
+
+  let(:config) { double }
+  let(:app_path) { File.join(tmp_dir, 'test/dummy') }
+
+  after do
+    FileUtils.remove_entry(tmp_dir)
+  end
+
+  describe '#on_rails', skip: 'Conflicts with manager in rspec_settings' do
+    it 'runs isolated code as if on Rails application' do
+      ### 1st run
+      #
+      expect(Dir.exist?(app_path)).to eq false
+      expect(defined?(Rails)).to be_nil
+      expect(config.instance_variable_defined?(:@rails)).to eq false
+
+      manager.on_rails do
+        expect(defined?(Rails)).not_to be_nil
+      end
+
+      expect(Dir.exist?(app_path)).to eq true
+      expect(defined?(Rails)).to be_nil
+      expect(config.instance_variable_defined?(:@rails)).to eq true
+
+      ### 2nd run
+      #
+      manager.on_rails do
+        expect(defined?(Rails)).not_to be_nil
+        expect(Rails).to eq config.instance_variable_get(:@rails)
+      end
+
+      expect(Dir.exist?(app_path)).to eq true
+      expect(defined?(Rails)).to be_nil
+      expect(config.instance_variable_defined?(:@rails)).to eq true
+    end
+  end
+
+  def tmp_dir
+    @tmp_dir ||= Dir.mktmpdir
+  end
+end

spec/uber_task/internal/path_spec.rb

@@ -25,20 +25,15 @@
       end
     end
 
-    context 'in rails' do
-      let(:rails_root) { Pathname.new(Dir.pwd) }
+    context 'on rails', :on_rails do
       let(:paths) do
         [
-          rails_root.join('abc').to_s,
+          Rails.root.join('abc').to_s,
           '/foo/bar/baz/gems/bar',
           '/foo/bar/rubygems/baz',
         ]
       end
 
-      before do
-        stub_const('Rails', double(root: rails_root))
-      end
-
       it 'shortens paths' do
         shortened = paths.map do |path|
           described_class.shorten(path)

spec/uber_task/logger_spec.rb

@@ -21,6 +21,14 @@
         end.to output(/some message/).to_stdout
       end
     end
+
+    context 'when Rails logger is defined', :on_rails do
+      it 'uses Rails logger by default' do
+        expect(Rails.logger).to receive(:info).with('some message')
+
+        described_class.logger.info('some message')
+      end
+    end
   end
 
   describe '.logger=' do