[ruby/pp] Support private instance_variables_to_inspect

(https://github.com/ruby/pp/pull/70)

* Support private instance_variables_to_inspect in pp

Ruby supports calling instance_variables_to_inspect even when
it is defined as a private method (ruby/ruby#13555).

This change aligns pp with Ruby's behavior.

https://github.com/ruby/pp/commit/8450e76db6

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/pp.rb b/lib/pp.rb
index fcd33ba80e..5fd29a373a 100644
--- a/lib/pp.rb
+++ b/lib/pp.rb
@@ -388,7 +388,7 @@ class PP < PrettyPrint
     # This method should return an array of names of instance variables as symbols or strings as:
     # +[:@a, :@b]+.
     def pretty_print_instance_variables
-      ivars = respond_to?(:instance_variables_to_inspect) ? instance_variables_to_inspect : instance_variables
+      ivars = respond_to?(:instance_variables_to_inspect, true) ? instance_variables_to_inspect || instance_variables : instance_variables
       ivars.sort
     end