From 14c6e04438d356e11e82269a8d79b96d9496543c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nicol=C3=B2=20Rebughini?= <nicolo.rebughini@pm.me>
Date: Wed, 22 Mar 2023 14:46:35 +0100
Subject: [PATCH] Do not allocate the first character when checking for
 relative paths
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This is the same optimization applied in
https://github.com/rails/rails/commit/a63ae913dfbb3813256144e52ae1063ac59edba4
which I proposed in https://github.com/rails/rails/pull/47714

Here's the benchmark:

require "bundler/inline"

ROOT_STRING = '/'
TEST_PATH = "/some/path"

gemfile(true) do
  source "https://rubygems.org"

  gem "benchmark-ips"
end

Benchmark.ips do |x|
  x.report("path[0]") do
   TEST_PATH[0] != ROOT_STRING
  end

  x.report("path.start_with?") do
   TEST_PATH.start_with?(ROOT_STRING)
  end

  x.compare!
end

Warming up --------------------------------------
             path[0]   942.044k i/100ms
    path.start_with?     1.556M i/100ms
Calculating -------------------------------------
             path[0]      9.463M (± 0.9%) i/s -     48.044M in   5.077358s
    path.start_with?     15.611M (± 0.2%) i/s -     79.352M in   5.083056s

Comparison:
    path.start_with?: 15611192.8 i/s
             path[0]:  9463245.0 i/s - 1.65x  slower
---
 actionpack/lib/action_dispatch/routing/redirection.rb | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/actionpack/lib/action_dispatch/routing/redirection.rb b/actionpack/lib/action_dispatch/routing/redirection.rb
index 054798ec7d..0ae7ce7a68 100644
--- a/actionpack/lib/action_dispatch/routing/redirection.rb
+++ b/actionpack/lib/action_dispatch/routing/redirection.rb
@@ -68,7 +68,7 @@ def inspect
 
       private
         def relative_path?(path)
-          path && !path.empty? && path[0] != "/"
+          path && !path.empty? && !path.start_with?("/")
         end
 
         def escape(params)