[ruby/irb] Revamp `help` command

(https://github.com/ruby/irb/pull/877)

* Make help command display help for individual commands

Usage: `help [command]`

If the command is not specified, it will display a list of all available commands.

If the command is specified, it will display the banner OR description of the command.

If the command is not found, it will display a message saying that the command is not found.

* Rename test/irb/cmd to test/irb/command

* Add banner to edit and ls commands

* Promote help command in the help message

1. Make `show_cmds` an alias of `help` so it's not displayed in the help message
2. Update description of the help command to reflect `help <command>` syntax

* Rename banner to help_message

https://github.com/ruby/irb/commit/43a2c99f3f

8 files changed, 113 insertions, 75 deletions

diff --git a/lib/irb.rb b/lib/irb.rb
index 73d96947ea..09ea9256cb 100644
--- a/lib/irb.rb
+++ b/lib/irb.rb
@@ -811,7 +811,7 @@ require_relative "irb/pager"
 #
 # === Commands
 #
-# Please use the `show_cmds` command to see the list of available commands.
+# Please use the `help` command to see the list of available commands.
 #
 # === IRB Sessions
 #
diff --git a/lib/irb/command.rb b/lib/irb/command.rb
index cab571cfe3..c84474e633 100644
--- a/lib/irb/command.rb
+++ b/lib/irb/command.rb
@@ -162,6 +162,7 @@ module IRB # :nodoc:
       [
         :irb_help, :Help, "command/help",
         [:help, NO_OVERRIDE],
+        [:show_cmds, NO_OVERRIDE],
       ],
 
       [
@@ -187,17 +188,11 @@ module IRB # :nodoc:
         :irb_show_source, :ShowSource, "command/show_source",
         [:show_source, NO_OVERRIDE],
       ],
-
       [
         :irb_whereami, :Whereami, "command/whereami",
         [:whereami, NO_OVERRIDE],
       ],
       [
-        :irb_show_cmds, :ShowCmds, "command/show_cmds",
-        [:show_cmds, NO_OVERRIDE],
-      ],
-
-      [
         :irb_history, :History, "command/history",
         [:history, NO_OVERRIDE],
         [:hist, NO_OVERRIDE],
diff --git a/lib/irb/command/base.rb b/lib/irb/command/base.rb
index 87d2fea356..880b781a46 100644
--- a/lib/irb/command/base.rb
+++ b/lib/irb/command/base.rb
@@ -22,12 +22,21 @@ module IRB
           @description
         end
 
+        def help_message(help_message = nil)
+          @help_message = help_message if help_message
+          @help_message
+        end
+
         private
 
         def string_literal?(args)
           sexp = Ripper.sexp(args)
           sexp && sexp.size == 2 && sexp.last&.first&.first == :string_literal
         end
+
+        def highlight(text)
+          Color.colorize(text, [:BOLD, :BLUE])
+        end
       end
 
       def self.execute(irb_context, *opts, **kwargs, &block)
diff --git a/lib/irb/command/edit.rb b/lib/irb/command/edit.rb
index 1a8ded6bcf..ab8c62663e 100644
--- a/lib/irb/command/edit.rb
+++ b/lib/irb/command/edit.rb
@@ -8,7 +8,23 @@ module IRB
   module Command
     class Edit < Base
       category "Misc"
-      description 'Open a file with the editor command defined with `ENV["VISUAL"]` or `ENV["EDITOR"]`.'
+      description 'Open a file or source location.'
+      help_message <<~HELP_MESSAGE
+        Usage: edit [FILE or constant or method signature]
+
+        Open a file in the editor specified in #{highlight('ENV["VISUAL"]')} or #{highlight('ENV["EDITOR"]')}
+
+        - If no arguments are provided, IRB will attempt to open the file the current context was defined in.
+        - If FILE is provided, IRB will open the file.
+        - If a constant or method signature is provided, IRB will attempt to locate the source file and open it.
+
+        Examples:
+
+          edit
+          edit foo.rb
+          edit Foo
+          edit Foo#bar
+      HELP_MESSAGE
 
       class << self
         def transform_args(args)
diff --git a/lib/irb/command/help.rb b/lib/irb/command/help.rb
index 67cc31a0bf..19113dbbfe 100644
--- a/lib/irb/command/help.rb
+++ b/lib/irb/command/help.rb
@@ -1,12 +1,84 @@
 # frozen_string_literal: true
 
-require_relative "show_cmds"
-
 module IRB
   module Command
-    class Help < ShowCmds
-      category "IRB"
-      description "List all available commands and their description."
+    class Help < Base
+      category "Help"
+      description "List all available commands. Use `help <command>` to get information about a specific command."
+
+      class << self
+        def transform_args(args)
+          # Return a string literal as is for backward compatibility
+          if args.empty? || string_literal?(args)
+            args
+          else # Otherwise, consider the input as a String for convenience
+            args.strip.dump
+          end
+        end
+      end
+
+      def execute(command_name = nil)
+        content =
+          if command_name
+            if command_class = ExtendCommandBundle.load_command(command_name)
+              command_class.help_message || command_class.description
+            else
+              "Can't find command `#{command_name}`. Please check the command name and try again.\n\n"
+            end
+          else
+            help_message
+          end
+        Pager.page_content(content)
+      end
+
+      private
+
+      def help_message
+        commands_info = IRB::ExtendCommandBundle.all_commands_info
+        commands_grouped_by_categories = commands_info.group_by { |cmd| cmd[:category] }
+
+        user_aliases = irb_context.instance_variable_get(:@user_aliases)
+
+        commands_grouped_by_categories["Aliases"] = user_aliases.map do |alias_name, target|
+          { display_name: alias_name, description: "Alias for `#{target}`" }
+        end
+
+        if irb_context.with_debugger
+          # Remove the original "Debugging" category
+          commands_grouped_by_categories.delete("Debugging")
+          # Add an empty "Debugging (from debug.gem)" category at the end
+          commands_grouped_by_categories["Debugging (from debug.gem)"] = []
+        end
+
+        longest_cmd_name_length = commands_info.map { |c| c[:display_name].length }.max
+
+        output = StringIO.new
+
+        help_cmds = commands_grouped_by_categories.delete("Help")
+
+        add_category_to_output("Help", help_cmds, output, longest_cmd_name_length)
+
+        commands_grouped_by_categories.each do |category, cmds|
+          add_category_to_output(category, cmds, output, longest_cmd_name_length)
+        end
+
+        # Append the debugger help at the end
+        if irb_context.with_debugger
+          output.puts DEBUGGER__.help
+        end
+
+        output.string
+      end
+
+      def add_category_to_output(category, cmds, output, longest_cmd_name_length)
+        output.puts Color.colorize(category, [:BOLD])
+
+        cmds.each do |cmd|
+          output.puts "  #{cmd[:display_name].to_s.ljust(longest_cmd_name_length)}    #{cmd[:description]}"
+        end
+
+        output.puts
+      end
     end
   end
 end
diff --git a/lib/irb/command/ls.rb b/lib/irb/command/ls.rb
index bbe4a1ee98..6b6136c2fe 100644
--- a/lib/irb/command/ls.rb
+++ b/lib/irb/command/ls.rb
@@ -12,7 +12,13 @@ module IRB
   module Command
     class Ls < Base
       category "Context"
-      description "Show methods, constants, and variables. `-g [query]` or `-G [query]` allows you to filter out the output."
+      description "Show methods, constants, and variables."
+
+      help_message <<~HELP_MESSAGE
+        Usage: ls [obj] [-g [query]]
+
+          -g [query]  Filter the output with a query.
+      HELP_MESSAGE
 
       def self.transform_args(args)
         if match = args&.match(/\A(?<args>.+\s|)(-g|-G)\s+(?<grep>[^\s]+)\s*\n\z/)
diff --git a/lib/irb/command/show_cmds.rb b/lib/irb/command/show_cmds.rb
deleted file mode 100644
index 940ed490d3..0000000000
--- a/lib/irb/command/show_cmds.rb
+++ /dev/null
@@ -1,59 +0,0 @@
-# frozen_string_literal: true
-
-require "stringio"
-
-require_relative "../pager"
-
-module IRB
-  # :stopdoc:
-
-  module Command
-    class ShowCmds < Base
-      category "IRB"
-      description "List all available commands and their description."
-
-      def execute(*args)
-        commands_info = IRB::ExtendCommandBundle.all_commands_info
-        commands_grouped_by_categories = commands_info.group_by { |cmd| cmd[:category] }
-
-        user_aliases = irb_context.instance_variable_get(:@user_aliases)
-
-        commands_grouped_by_categories["Aliases"] = user_aliases.map do |alias_name, target|
-          { display_name: alias_name, description: "Alias for `#{target}`" }
-        end
-
-        if irb_context.with_debugger
-          # Remove the original "Debugging" category
-          commands_grouped_by_categories.delete("Debugging")
-          # Remove the `help` command as it's delegated to the debugger
-          commands_grouped_by_categories["Context"].delete_if { |cmd| cmd[:display_name] == :help }
-          # Add an empty "Debugging (from debug.gem)" category at the end
-          commands_grouped_by_categories["Debugging (from debug.gem)"] = []
-        end
-
-        longest_cmd_name_length = commands_info.map { |c| c[:display_name].length }.max
-
-        output = StringIO.new
-
-        commands_grouped_by_categories.each do |category, cmds|
-          output.puts Color.colorize(category, [:BOLD])
-
-          cmds.each do |cmd|
-            output.puts "  #{cmd[:display_name].to_s.ljust(longest_cmd_name_length)}    #{cmd[:description]}"
-          end
-
-          output.puts
-        end
-
-        # Append the debugger help at the end
-        if irb_context.with_debugger
-          output.puts DEBUGGER__.help
-        end
-
-        Pager.page_content(output.string)
-      end
-    end
-  end
-
-  # :startdoc:
-end
diff --git a/lib/irb/statement.rb b/lib/irb/statement.rb
index 009eb2d20b..1e026d112f 100644
--- a/lib/irb/statement.rb
+++ b/lib/irb/statement.rb
@@ -83,9 +83,8 @@ module IRB
       end
 
       def should_be_handled_by_debugger?
-        require_relative 'command/help'
         require_relative 'command/debug'
-        IRB::Command::DebugCommand > @command_class || IRB::Command::Help == @command_class
+        IRB::Command::DebugCommand > @command_class
       end
 
       def evaluable_code