From 3ce5d89c206a54cbf32032674c9edf6f649e95f6 Mon Sep 17 00:00:00 2001
From: Jeremy Evans <code@jeremyevans.net>
Date: Sat, 19 Apr 2025 23:47:36 -0700
Subject: [PATCH] [ruby/pp] Avoid an array allocation per element in list
 passed to seplist

The array allocation was because the keyword splat expression is
not recognized as safe by the compiler.  Also avoid unnecessary
>= method call per element.  This uses a private constant to
avoid unnecessary work at runtime.

I assume the only reason this code is needed is because v may
end with a ruby2_keywords hash that we do not want to treat as
keywords.

This issue was found by the performance warning in Ruby feature
21274.

https://github.com/ruby/pp/commit/3bf6df0e5c
---
 lib/pp.rb | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/lib/pp.rb b/lib/pp.rb
index 332062164d..d86bfb9119 100644
--- a/lib/pp.rb
+++ b/lib/pp.rb
@@ -276,15 +276,20 @@ class PP < PrettyPrint
     def seplist(list, sep=nil, iter_method=:each) # :yield: element
       sep ||= lambda { comma_breakable }
       first = true
+      kwsplat = EMPTY_HASH
       list.__send__(iter_method) {|*v|
         if first
           first = false
         else
           sep.call
         end
-        RUBY_VERSION >= "3.0" ? yield(*v, **{}) : yield(*v)
+        kwsplat ? yield(*v, **kwsplat) : yield(*v)
       }
     end
+    EMPTY_HASH = if RUBY_VERSION >= "3.0"
+      {}.freeze
+    end
+    private_constant :EMPTY_HASH
 
     # A present standard failsafe for pretty printing any given Object
     def pp_object(obj)