[ruby/irb] Fix nested IRB sessions' history saving

(https://github.com/ruby/irb/pull/652)

1. Dynamically including `HistorySavingAbility` makes things unnecessarily
   complicated and should be avoided.
2. Because both `Reline` and `Readline` use a single `HISTORY` constant
   to store history data. When nesting IRB sessions, only the first IRB
   session should handle history loading and saving so we can avoid
   duplicating history.
3. History saving callback should NOT be stored in `IRB.conf` as it's
   recreated every time `IRB.setup` is called, which would happen when
   nesting IRB sessions.

https://github.com/ruby/irb/commit/0fef0ae160

1 files changed, 4 insertions, 8 deletions

diff --git a/lib/irb/input-method.rb b/lib/irb/input-method.rb
index 4dc43abba3..245b935668 100644
--- a/lib/irb/input-method.rb
+++ b/lib/irb/input-method.rb
@@ -5,6 +5,7 @@
 #
 
 require_relative 'completion'
+require_relative "history"
 require 'io/console'
 require 'reline'
 
@@ -167,6 +168,8 @@ module IRB
         include ::Readline
       end
 
+      include HistorySavingAbility
+
       # Creates a new input method object using Readline
       def initialize
         self.class.initialize_readline
@@ -219,10 +222,6 @@ module IRB
         true
       end
 
-      def support_history_saving?
-        true
-      end
-
       # Returns the current line number for #io.
       #
       # #line counts the number of times #gets is called.
@@ -250,6 +249,7 @@ module IRB
 
   class RelineInputMethod < InputMethod
     HISTORY = Reline::HISTORY
+    include HistorySavingAbility
     # Creates a new input method object using Reline
     def initialize
       IRB.__send__(:set_encoding, Reline.encoding_system_needs.name, override: false)
@@ -451,10 +451,6 @@ module IRB
       str += " and #{inputrc_path}" if File.exist?(inputrc_path)
       str
     end
-
-    def support_history_saving?
-      true
-    end
   end
 
   class ReidlineInputMethod < RelineInputMethod