Import rubocop-daemon

Preparing to resolve #9503.

This PR imports https://github.com/fohte/rubocop-daemon into RuboCop core.

The rubocop-daemon's original license (MIT) is written at the beginning
of the imported files.

lib/rubocop/daemon.rb

@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+
+#
+# This code is based on https://github.com/fohte/rubocop-daemon.
+#
+# Copyright (c) 2018 Hayato Kawai
+#
+# The MIT License (MIT)
+#
+# https://github.com/fohte/rubocop-daemon/blob/master/LICENSE.txt
+#
+module RuboCop
+  module Daemon
+    TIMEOUT = 20
+
+    autoload :CLI, 'rubocop/daemon/cli'
+    autoload :Cache, 'rubocop/daemon/cache'
+    autoload :ClientCommand, 'rubocop/daemon/client_command'
+    autoload :Helper, 'rubocop/daemon/helper'
+    autoload :Server, 'rubocop/daemon/server'
+    autoload :ServerCommand, 'rubocop/daemon/server_command'
+    autoload :SocketReader, 'rubocop/daemon/socket_reader'
+
+    def self.running?
+      Cache.dir.exist? && Cache.pid_path.file? && Cache.pid_running?
+    end
+
+    def self.wait_for_running_status!(expected)
+      start_time = Time.now
+      while Daemon.running? != expected
+        sleep 0.1
+        next unless Time.now - start_time > TIMEOUT
+
+        warn "running? was not #{expected} after #{TIMEOUT} seconds!"
+        exit 1
+      end
+    end
+  end
+end
+
+require 'rubocop/daemon/errors'

lib/rubocop/daemon/cache.rb

@@ -0,0 +1,97 @@
+# frozen_string_literal: true
+
+require 'pathname'
+
+#
+# This code is based on https://github.com/fohte/rubocop-daemon.
+#
+# Copyright (c) 2018 Hayato Kawai
+#
+# The MIT License (MIT)
+#
+# https://github.com/fohte/rubocop-daemon/blob/master/LICENSE.txt
+#
+module RuboCop
+  module Daemon
+    class Cache
+      class << self
+        # Searches for Gemfile or gems.rb in the current dir or any parent dirs
+        def project_dir
+          current_dir = Dir.pwd
+          while current_dir != '/'
+            return current_dir if %w[Gemfile gems.rb].any? do |gemfile|
+              File.exist?(File.join(current_dir, gemfile))
+            end
+
+            current_dir = File.expand_path('..', current_dir)
+          end
+          # If we can't find a Gemfile, just use the current directory
+          Dir.pwd
+        end
+
+        def project_dir_cache_key
+          @project_dir_cache_key ||= project_dir[1..-1].tr('/', '+')
+        end
+
+        def dir
+          cache_path = File.expand_path('~/.cache/rubocop-daemon')
+          Pathname.new(File.join(cache_path, project_dir_cache_key)).tap do |d|
+            d.mkpath unless d.exist?
+          end
+        end
+
+        def port_path
+          dir.join('port')
+        end
+
+        def token_path
+          dir.join('token')
+        end
+
+        def pid_path
+          dir.join('pid')
+        end
+
+        def lock_path
+          dir.join('lock')
+        end
+
+        def status_path
+          dir.join('status')
+        end
+
+        def pid_running?
+          Process.kill(0, pid_path.read.to_i) == 1
+        rescue Errno::ESRCH
+          false
+        end
+
+        def acquire_lock
+          lock_file = File.open(lock_path, File::CREAT)
+          # flock returns 0 if successful, and false if not.
+          flock_result = lock_file.flock(File::LOCK_EX | File::LOCK_NB)
+          yield flock_result != false
+        ensure
+          lock_file.flock(File::LOCK_UN)
+          lock_file.close
+        end
+
+        def write_port_and_token_files(port:, token:)
+          port_path.write(port)
+          token_path.write(token)
+        end
+
+        def write_pid_file
+          pid_path.write(Process.pid)
+          yield
+        ensure
+          dir.rmtree
+        end
+
+        def write_status_file(status)
+          status_path.write(status)
+        end
+      end
+    end
+  end
+end

lib/rubocop/daemon/cli.rb

@@ -0,0 +1,62 @@
+# frozen_string_literal: true
+
+require 'optparse'
+
+#
+# This code is based on https://github.com/fohte/rubocop-daemon.
+#
+# Copyright (c) 2018 Hayato Kawai
+#
+# The MIT License (MIT)
+#
+# https://github.com/fohte/rubocop-daemon/blob/master/LICENSE.txt
+#
+module RuboCop
+  module Daemon
+    class CLI
+      def self.new_parser(&_block)
+        OptionParser.new do |opts|
+          yield(opts)
+        end
+      end
+
+      def run(argv = ARGV)
+        parser.order!(argv)
+        return if argv.empty?
+
+        create_subcommand_instance(argv)
+      rescue OptionParser::InvalidOption => e
+        warn "error: #{e.message}"
+        exit 1
+      rescue UnknownClientCommandError => e
+        warn "rubocop-daemon: #{e.message}. See 'rubocop-daemon --help'."
+        exit 1
+      end
+
+      def parser
+        @parser ||= self.class.new_parser do |opts|
+          opts.banner = 'usage: rubocop-daemon <command> [<args>]'
+        end
+      end
+
+      private
+
+      def create_subcommand_instance(argv)
+        subcommand, *args = argv
+        find_subcommand_class(subcommand).new(args).run
+      end
+
+      def find_subcommand_class(subcommand)
+        case subcommand
+        when 'exec' then ClientCommand::Exec
+        when 'restart' then ClientCommand::Restart
+        when 'start' then ClientCommand::Start
+        when 'status' then ClientCommand::Status
+        when 'stop' then ClientCommand::Stop
+        else
+          raise UnknownClientCommandError, "#{subcommand.inspect} is not a rubocop-daemon command"
+        end
+      end
+    end
+  end
+end

lib/rubocop/daemon/client_command.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+#
+# This code is based on https://github.com/fohte/rubocop-daemon.
+#
+# Copyright (c) 2018 Hayato Kawai
+#
+# The MIT License (MIT)
+#
+# https://github.com/fohte/rubocop-daemon/blob/master/LICENSE.txt
+#
+module RuboCop
+  module Daemon
+    module ClientCommand
+      autoload :Base, 'rubocop/daemon/client_command/base'
+      autoload :Exec, 'rubocop/daemon/client_command/exec'
+      autoload :Restart, 'rubocop/daemon/client_command/restart'
+      autoload :Start, 'rubocop/daemon/client_command/start'
+      autoload :Status, 'rubocop/daemon/client_command/status'
+      autoload :Stop, 'rubocop/daemon/client_command/stop'
+    end
+  end
+end

lib/rubocop/daemon/client_command/base.rb

@@ -0,0 +1,51 @@
+# frozen_string_literal: true
+
+require 'shellwords'
+require 'socket'
+
+#
+# This code is based on https://github.com/fohte/rubocop-daemon.
+#
+# Copyright (c) 2018 Hayato Kawai
+#
+# The MIT License (MIT)
+#
+# https://github.com/fohte/rubocop-daemon/blob/master/LICENSE.txt
+#
+module RuboCop
+  module Daemon
+    module ClientCommand
+      class Base
+        def initialize(argv)
+          @argv = argv.dup
+          @options = {}
+        end
+
+        def run; end
+
+        private
+
+        def send_request(command:, args: [], body: '')
+          TCPSocket.open('127.0.0.1', Cache.port_path.read) do |socket|
+            socket.puts [Cache.token_path.read, Dir.pwd, command, *args].shelljoin
+            socket.write body
+            socket.close_write
+            STDOUT.write socket.read(4096) until socket.eof?
+          end
+        end
+
+        def check_running_server
+          Daemon.running?.tap do |running|
+            warn 'rubocop-daemon: server is not running.' unless running
+          end
+        end
+
+        def ensure_server!
+          return if check_running_server
+
+          ClientCommand::Start.new([]).run
+        end
+      end
+    end
+  end
+end

lib/rubocop/daemon/client_command/exec.rb

@@ -0,0 +1,47 @@
+# frozen_string_literal: true
+
+#
+# This code is based on https://github.com/fohte/rubocop-daemon.
+#
+# Copyright (c) 2018 Hayato Kawai
+#
+# The MIT License (MIT)
+#
+# https://github.com/fohte/rubocop-daemon/blob/master/LICENSE.txt
+#
+module RuboCop
+  module Daemon
+    module ClientCommand
+      class Exec < Base
+        def run
+          args = parser.parse(@argv)
+          ensure_server!
+          Cache.status_path.delete if Cache.status_path.file?
+          send_request(
+            command: 'exec',
+            args: args,
+            body: $stdin.tty? ? '' : $stdin.read,
+          )
+          exit_with_status!
+        end
+
+        private
+
+        def parser
+          @parser ||= CLI.new_parser do |p|
+            p.banner = 'usage: rubocop-daemon exec [options] [files...] [-- [rubocop-options]]'
+          end
+        end
+
+        def exit_with_status!
+          raise "rubocop-daemon: Could not find status file at: #{Cache.status_path}" unless Cache.status_path.file?
+
+          status = Cache.status_path.read
+          raise "rubocop-daemon: '#{status}' is not a valid status!" if (status =~ /^\d+$/).nil?
+
+          exit status.to_i
+        end
+      end
+    end
+  end
+end

lib/rubocop/daemon/client_command/restart.rb

@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+
+#
+# This code is based on https://github.com/fohte/rubocop-daemon.
+#
+# Copyright (c) 2018 Hayato Kawai
+#
+# The MIT License (MIT)
+#
+# https://github.com/fohte/rubocop-daemon/blob/master/LICENSE.txt
+#
+module RuboCop
+  module Daemon
+    module ClientCommand
+      class Restart < Base
+        def run
+          parser.parse(@argv)
+
+          ClientCommand::Stop.new([]).run
+          ClientCommand::Start.new(@argv).run
+        end
+
+        private
+
+        def parser
+          @parser ||= CLI.new_parser do |p|
+            p.banner = 'usage: rubocop-daemon restart'
+
+            p.on('-p', '--port [PORT]') { |v| @options[:port] = v }
+          end
+        end
+      end
+    end
+  end
+end