[ruby/irb] Stop treating history-saving logic as extension

(https://github.com/ruby/irb/pull/613)

Since `IRB.conf[:SAVE_HISTORY]` is assigned with 1000 by default, history-saving
is a feature enabled by default. So it should not be treated as an extension,
which adds unnecessary complexity to the code.

4 files changed, 28 insertions, 54 deletions

diff --git a/lib/irb/context.rb b/lib/irb/context.rb
index 6f209b596a..d755622f32 100644
--- a/lib/irb/context.rb
+++ b/lib/irb/context.rb
@@ -8,6 +8,7 @@ require_relative "workspace"
 require_relative "inspector"
 require_relative "input-method"
 require_relative "output-method"
+require_relative "history"
 
 module IRB
   # A class that wraps the current state of the irb session, including the
@@ -151,6 +152,27 @@ module IRB
       @command_aliases = IRB.conf[:COMMAND_ALIASES]
     end
 
+    def save_history=(val)
+      IRB.conf[:SAVE_HISTORY] = val
+      if val
+        (IRB.conf[:MAIN_CONTEXT] || self).init_save_history
+      end
+    end
+
+    def save_history
+      IRB.conf[:SAVE_HISTORY]
+    end
+
+    # A copy of the default <code>IRB.conf[:HISTORY_FILE]</code>
+    def history_file
+      IRB.conf[:HISTORY_FILE]
+    end
+
+    # Set <code>IRB.conf[:HISTORY_FILE]</code> to the given +hist+.
+    def history_file=(hist)
+      IRB.conf[:HISTORY_FILE] = hist
+    end
+
     # The top-level workspace, see WorkSpace#main
     def main
       @workspace.main
@@ -554,5 +576,11 @@ module IRB
       command = command_aliases.fetch(command.to_sym, command)
       ExtendCommandBundle.load_command(command)&.respond_to?(:transform_args)
     end
+
+    def init_save_history# :nodoc:
+      unless (class<<@io;self;end).include?(HistorySavingAbility)
+        @io.extend(HistorySavingAbility)
+      end
+    end
   end
 end
diff --git a/lib/irb/extend-command.rb b/lib/irb/extend-command.rb
index 8b074262ee..7238f1fd1c 100644
--- a/lib/irb/extend-command.rb
+++ b/lib/irb/extend-command.rb
@@ -319,7 +319,6 @@ module IRB # :nodoc:
       [:eval_history=, "ext/history.rb"],
       [:use_tracer=, "ext/tracer.rb"],
       [:use_loader=, "ext/use-loader.rb"],
-      [:save_history=, "ext/save-history.rb"],
     ]
 
     # Installs the default context extensions as irb commands:
@@ -327,7 +326,6 @@ module IRB # :nodoc:
     # Context#eval_history=::   +irb/ext/history.rb+
     # Context#use_tracer=::     +irb/ext/tracer.rb+
     # Context#use_loader=::     +irb/ext/use-loader.rb+
-    # Context#save_history=::   +irb/ext/save-history.rb+
     def self.install_extend_commands
       for args in @EXTEND_COMMANDS
         def_extend_command(*args)
diff --git a/lib/irb/ext/save-history.rb b/lib/irb/history.rb
index b1987ea646..a1b0d5cba0 100644
--- a/lib/irb/ext/save-history.rb
+++ b/lib/irb/history.rb
@@ -1,56 +1,5 @@
-# frozen_string_literal: false
-#
-#   save-history.rb -
-#   	by Keiju ISHITSUKA(keiju@ruby-lang.org)
-#
-
 module IRB
   module HistorySavingAbility # :nodoc:
-  end
-
-  class Context
-    def init_save_history# :nodoc:
-      unless (class<<@io;self;end).include?(HistorySavingAbility)
-        @io.extend(HistorySavingAbility)
-      end
-    end
-
-    # A copy of the default <code>IRB.conf[:SAVE_HISTORY]</code>
-    def save_history
-      IRB.conf[:SAVE_HISTORY]
-    end
-
-    remove_method(:save_history=) if method_defined?(:save_history=)
-    # Sets <code>IRB.conf[:SAVE_HISTORY]</code> to the given +val+ and calls
-    # #init_save_history with this context.
-    #
-    # Will store the number of +val+ entries of history in the #history_file
-    #
-    # Add the following to your +.irbrc+ to change the number of history
-    # entries stored to 1000:
-    #
-    #     IRB.conf[:SAVE_HISTORY] = 1000
-    def save_history=(val)
-      IRB.conf[:SAVE_HISTORY] = val
-      if val
-        main_context = IRB.conf[:MAIN_CONTEXT]
-        main_context = self unless main_context
-        main_context.init_save_history
-      end
-    end
-
-    # A copy of the default <code>IRB.conf[:HISTORY_FILE]</code>
-    def history_file
-      IRB.conf[:HISTORY_FILE]
-    end
-
-    # Set <code>IRB.conf[:HISTORY_FILE]</code> to the given +hist+.
-    def history_file=(hist)
-      IRB.conf[:HISTORY_FILE] = hist
-    end
-  end
-
-  module HistorySavingAbility # :nodoc:
     def HistorySavingAbility.extended(obj)
       IRB.conf[:AT_EXIT].push proc{obj.save_history}
       obj.load_history
diff --git a/test/irb/test_history.rb b/test/irb/test_history.rb
index fc81d53005..f0dfa03c6f 100644
--- a/test/irb/test_history.rb
+++ b/test/irb/test_history.rb
@@ -1,6 +1,5 @@
 # frozen_string_literal: false
 require 'irb'
-require 'irb/ext/save-history'
 require 'readline'
 
 require_relative "helper"