Add commands to start and use the debugger (#449)

* Seamlessly integrate a few debug commands

* Improve the break command support

* Utilize skip_src option if available

* Add step and delete commands

* Write end-to-end tests for each debugger command

* Add documentation

* Add backtrace, info, catch commands

Gemfile

@@ -11,4 +11,5 @@ group :development do
   gem "stackprof" if is_unix && !is_truffleruby
   gem "test-unit"
   gem "reline", github: "ruby/reline" if ENV["WITH_LATEST_RELINE"] == "true"
+  gem "debug"
 end

README.md

@@ -90,6 +90,8 @@ The following commands are available on IRB.
   * Show the source code around binding.irb again.
 * `debug`
   * Start the debugger of debug.gem.
+* `break`, `delete`, `next`, `step`, `continue`, `finish`, `backtrace`, `info`, `catch`
+  * Start the debugger of debug.gem and run the command on it.
 
 ## Documentation
 

lib/irb.rb

@@ -96,6 +96,8 @@
 #   * Show the source code around binding.irb again.
 # * debug
 #   * Start the debugger of debug.gem.
+# * break, delete, next, step, continue, finish, backtrace, info, catch
+#   * Start the debugger of debug.gem and run the command on it.
 #
 # == Configuration
 #
@@ -470,10 +472,6 @@ class Irb
     def initialize(workspace = nil, input_method = nil)
       @context = Context.new(self, workspace, input_method)
       @context.main.extend ExtendCommandBundle
-      @context.command_aliases.each do |alias_name, cmd_name|
-        next if @context.symbol_alias(alias_name)
-        @context.main.install_alias_method(alias_name, cmd_name)
-      end
       @signal_status = :IN_IRB
       @scanner = RubyLex.new
     end

lib/irb/cmd/backtrace.rb

@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+require_relative "debug"
+
+module IRB
+  # :stopdoc:
+
+  module ExtendCommand
+    class Backtrace < Debug
+      def self.transform_args(args)
+        args&.dump
+      end
+
+      def execute(*args)
+        super(pre_cmds: ["backtrace", *args].join(" "))
+      end
+    end
+  end
+
+  # :startdoc:
+end

lib/irb/cmd/break.rb

@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+require_relative "debug"
+
+module IRB
+  # :stopdoc:
+
+  module ExtendCommand
+    class Break < Debug
+      def self.transform_args(args)
+        args&.dump
+      end
+
+      def execute(args = nil)
+        super(pre_cmds: "break #{args}")
+      end
+    end
+  end
+
+  # :startdoc:
+end

lib/irb/cmd/catch.rb

@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+require_relative "debug"
+
+module IRB
+  # :stopdoc:
+
+  module ExtendCommand
+    class Catch < Debug
+      def self.transform_args(args)
+        args&.dump
+      end
+
+      def execute(*args)
+        super(pre_cmds: ["catch", *args].join(" "))
+      end
+    end
+  end
+
+  # :startdoc:
+end

lib/irb/cmd/continue.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+require_relative "debug"
+
+module IRB
+  # :stopdoc:
+
+  module ExtendCommand
+    class Continue < Debug
+      def execute(*args)
+        super(do_cmds: ["continue", *args].join(" "))
+      end
+    end
+  end
+
+  # :startdoc:
+end

lib/irb/cmd/debug.rb

@@ -11,7 +11,7 @@ class Debug < Nop
       ].map { |file| /\A#{Regexp.escape(file)}:\d+:in `irb'\z/ }
       IRB_DIR = File.expand_path('..', __dir__)
 
-      def execute(*args)
+      def execute(pre_cmds: nil, do_cmds: nil)
         unless binding_irb?
           puts "`debug` command is only available when IRB is started with binding.irb"
           return
@@ -25,11 +25,19 @@ def execute(*args)
           return
         end
 
+        options = { oneshot: true, hook_call: false }
+        if pre_cmds || do_cmds
+          options[:command] = ['irb', pre_cmds, do_cmds]
+        end
+        if DEBUGGER__::LineBreakpoint.instance_method(:initialize).parameters.include?([:key, :skip_src])
+          options[:skip_src] = true
+        end
+
         # To make debugger commands like `next` or `continue` work without asking
         # the user to quit IRB after that, we need to exit IRB first and then hit
         # a TracePoint on #debug_break.
         file, lineno = IRB::Irb.instance_method(:debug_break).source_location
-        DEBUGGER__::SESSION.add_line_breakpoint(file, lineno + 1, oneshot: true, hook_call: false)
+        DEBUGGER__::SESSION.add_line_breakpoint(file, lineno + 1, **options)
         # exit current Irb#run call
         throw :IRB_EXIT
       end

lib/irb/cmd/delete.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+require_relative "debug"
+
+module IRB
+  # :stopdoc:
+
+  module ExtendCommand
+    class Delete < Debug
+      def execute(*args)
+        super(pre_cmds: ["delete", *args].join(" "))
+      end
+    end
+  end
+
+  # :startdoc:
+end

lib/irb/cmd/finish.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+require_relative "debug"
+
+module IRB
+  # :stopdoc:
+
+  module ExtendCommand
+    class Finish < Debug
+      def execute(*args)
+        super(do_cmds: ["finish", *args].join(" "))
+      end
+    end
+  end
+
+  # :startdoc:
+end

lib/irb/cmd/info.rb

@@ -1,31 +1,18 @@
-# frozen_string_literal: false
+# frozen_string_literal: true
 
-require_relative "nop"
+require_relative "debug"
 
 module IRB
   # :stopdoc:
 
   module ExtendCommand
-    class Info < Nop
-      def execute
-        Class.new {
-          def inspect
-            str  = "Ruby version: #{RUBY_VERSION}\n"
-            str += "IRB version: #{IRB.version}\n"
-            str += "InputMethod: #{IRB.CurrentContext.io.inspect}\n"
-            str += ".irbrc path: #{IRB.rc_file}\n" if File.exist?(IRB.rc_file)
-            str += "RUBY_PLATFORM: #{RUBY_PLATFORM}\n"
-            str += "LANG env: #{ENV["LANG"]}\n" if ENV["LANG"] && !ENV["LANG"].empty?
-            str += "LC_ALL env: #{ENV["LC_ALL"]}\n" if ENV["LC_ALL"] && !ENV["LC_ALL"].empty?
-            str += "East Asian Ambiguous Width: #{Reline.ambiguous_width.inspect}\n"
-            if RbConfig::CONFIG['host_os'] =~ /mswin|msys|mingw|cygwin|bccwin|wince|emc/
-              codepage = `chcp`.b.sub(/.*: (\d+)\n/, '\1')
-              str += "Code page: #{codepage}\n"
-            end
-            str
-          end
-          alias_method :to_s, :inspect
-        }.new
+    class Info < Debug
+      def self.transform_args(args)
+        args&.dump
+      end
+
+      def execute(*args)
+        super(pre_cmds: ["info", *args].join(" "))
       end
     end
   end

lib/irb/cmd/irb_info.rb

@@ -0,0 +1,34 @@
+# frozen_string_literal: false
+
+require_relative "nop"
+
+module IRB
+  # :stopdoc:
+
+  module ExtendCommand
+    class IrbInfo < Nop
+      def execute
+        Class.new {
+          def inspect
+            str  = "Ruby version: #{RUBY_VERSION}\n"
+            str += "IRB version: #{IRB.version}\n"
+            str += "InputMethod: #{IRB.CurrentContext.io.inspect}\n"
+            str += ".irbrc path: #{IRB.rc_file}\n" if File.exist?(IRB.rc_file)
+            str += "RUBY_PLATFORM: #{RUBY_PLATFORM}\n"
+            str += "LANG env: #{ENV["LANG"]}\n" if ENV["LANG"] && !ENV["LANG"].empty?
+            str += "LC_ALL env: #{ENV["LC_ALL"]}\n" if ENV["LC_ALL"] && !ENV["LC_ALL"].empty?
+            str += "East Asian Ambiguous Width: #{Reline.ambiguous_width.inspect}\n"
+            if RbConfig::CONFIG['host_os'] =~ /mswin|msys|mingw|cygwin|bccwin|wince|emc/
+              codepage = `chcp`.b.sub(/.*: (\d+)\n/, '\1')
+              str += "Code page: #{codepage}\n"
+            end
+            str
+          end
+          alias_method :to_s, :inspect
+        }.new
+      end
+    end
+  end
+
+  # :startdoc:
+end

lib/irb/cmd/next.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+require_relative "debug"
+
+module IRB
+  # :stopdoc:
+
+  module ExtendCommand
+    class Next < Debug
+      def execute(*args)
+        super(do_cmds: ["next", *args].join(" "))
+      end
+    end
+  end
+
+  # :startdoc:
+end

lib/irb/cmd/step.rb

@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+require_relative "debug"
+
+module IRB
+  # :stopdoc:
+
+  module ExtendCommand
+    class Step < Debug
+      def execute(*args)
+        # Run `next` first to move out of binding.irb
+        super(pre_cmds: "next", do_cmds: ["step", *args].join(" "))
+      end
+    end
+  end
+
+  # :startdoc:
+end

lib/irb/context.rb

@@ -486,9 +486,9 @@ def evaluate(line, line_no, exception: nil) # :nodoc:
         @workspace.local_variable_set(:_, exception)
       end
 
-      # Transform a non-identifier alias (ex: @, $)
+      # Transform a non-identifier alias (@, $) or keywords (next, break)
       command, args = line.split(/\s/, 2)
-      if original = symbol_alias(command)
+      if original = command_aliases[command.to_sym]
         line = line.gsub(/\A#{Regexp.escape(command)}/, original.to_s)
         command = original
       end
@@ -545,10 +545,16 @@ def local_variables # :nodoc:
       workspace.binding.local_variables
     end
 
-    # Return a command name if it's aliased from the argument and it's not an identifier.
-    def symbol_alias(command)
+    # Return true if it's aliased from the argument and it's not an identifier.
+    def symbol_alias?(command)
       return nil if command.match?(/\A\w+\z/)
-      command_aliases[command.to_sym]
+      command_aliases.key?(command.to_sym)
+    end
+
+    # Return true if the command supports transforming args
+    def transform_args?(command)
+      command = command_aliases.fetch(command.to_sym, command)
+      ExtendCommandBundle.load_command(command)&.respond_to?(:transform_args)
     end
   end
 end

lib/irb/extend-command.rb

@@ -124,13 +124,48 @@ def irb_context
         :irb_edit, :Edit, "cmd/edit",
         [:edit, NO_OVERRIDE],
       ],
+      [
+        :irb_break, :Break, "cmd/break",
+      ],
+      [
+        :irb_catch, :Catch, "cmd/catch",
+      ],
+      [
+        :irb_next, :Next, "cmd/next",
+      ],
+      [
+        :irb_delete, :Delete, "cmd/delete",
+        [:delete, NO_OVERRIDE],
+      ],
+      [
+        :irb_step, :Step, "cmd/step",
+        [:step, NO_OVERRIDE],
+      ],
+      [
+        :irb_continue, :Continue, "cmd/continue",
+        [:continue, NO_OVERRIDE],
+      ],
+      [
+        :irb_finish, :Finish, "cmd/finish",
+        [:finish, NO_OVERRIDE],
+      ],
+      [
+        :irb_backtrace, :Backtrace, "cmd/backtrace",
+        [:backtrace, NO_OVERRIDE],
+        [:bt, NO_OVERRIDE],
+      ],
+      [
+        :irb_debug_info, :Info, "cmd/info",
+        [:info, NO_OVERRIDE],
+      ],
+
       [
         :irb_help, :Help, "cmd/help",
         [:help, NO_OVERRIDE],
       ],
 
       [
-        :irb_info, :Info, "cmd/info"
+        :irb_info, :IrbInfo, "cmd/irb_info"
       ],
 
       [

lib/irb/init.rb

@@ -160,8 +160,13 @@ def IRB.init_config(ap_path)
     @CONF[:AT_EXIT] = []
 
     @CONF[:COMMAND_ALIASES] = {
+      # Symbol aliases
       :'$' => :show_source,
       :'@' => :whereami,
+      # Keyword aliases
+      :break => :irb_break,
+      :catch => :irb_catch,
+      :next => :irb_next,
     }
   end