[ruby/irb] Fix history-saving feature

(https://github.com/ruby/irb/pull/642)

* Define RelineInputMethod::HISTORY

The HistorySavingAbility module doesn't do anything if the input method
class doesn't define HISTORY.

- https://github.com/ruby/irb/blob/3ac96be660bf052902fb4e532c7a46cf294b71eb/lib/irb/history.rb#L10
- https://github.com/ruby/irb/blob/3ac96be660bf052902fb4e532c7a46cf294b71eb/lib/irb/history.rb#L34

This patch defines RelineInputMethod::HISTORY to avoid this.

* Improve history-saving's ability check

Instead of checking the existence of `input_method_class::HISTORY`, we should
make every input method class declare if it supports history saving or not.

Since the default value is `false`, it shouldn't break any custom input method
that inherits from `IRB::InputMethod`.

https://github.com/ruby/irb/commit/aec7a5b3f5

1 files changed, 5 insertions, 7 deletions

diff --git a/lib/irb/context.rb b/lib/irb/context.rb
index d755622f32..bf5b4c5708 100644
--- a/lib/irb/context.rb
+++ b/lib/irb/context.rb
@@ -154,8 +154,12 @@ module IRB
 
     def save_history=(val)
       IRB.conf[:SAVE_HISTORY] = val
+
       if val
-        (IRB.conf[:MAIN_CONTEXT] || self).init_save_history
+        context = (IRB.conf[:MAIN_CONTEXT] || self)
+        if context.io.support_history_saving? && !context.io.singleton_class.include?(HistorySavingAbility)
+          context.io.extend(HistorySavingAbility)
+        end
       end
     end
 
@@ -576,11 +580,5 @@ 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