[ruby/irb] Suppress command return values

(https://github.com/ruby/irb/pull/934)

Since commands can't be chained with methods, their return values are
not intended to be used. But if IRB keeps storing command return values
as the last value, and print them, users may rely on such implicit
behaviour.

So to avoid such confusion, this commit suppresses command's
return values. It also updates some commands that currently rely on
this implicit behaviour.

https://github.com/ruby/irb/commit/fa96bea76f

1 files changed, 4 insertions, 3 deletions

diff --git a/lib/irb/context.rb b/lib/irb/context.rb
index 836b8d2625..22e855f1ef 100644
--- a/lib/irb/context.rb
+++ b/lib/irb/context.rb
@@ -587,18 +587,19 @@ module IRB
 
     def evaluate(statement, line_no) # :nodoc:
       @line_no = line_no
-      result = nil
 
       case statement
       when Statement::EmptyInput
         return
       when Statement::Expression
         result = evaluate_expression(statement.code, line_no)
+        set_last_value(result)
       when Statement::Command
-        result = statement.command_class.execute(self, statement.arg)
+        statement.command_class.execute(self, statement.arg)
+        set_last_value(nil)
       end
 
-      set_last_value(result)
+      nil
     end
 
     def evaluate_expression(code, line_no) # :nodoc: