From 03bf6db08c0bdc9a99f818088217099ead5baea0 Mon Sep 17 00:00:00 2001
From: Mike McQuaid <mike@mikemcquaid.com>
Date: Thu, 16 May 2024 11:08:51 +0900
Subject: [PATCH] utils/gems: handle undefined `HOMEBREW_CACHE`.

Some call paths can result in this not being defined so let's handle
that better.
---
 Library/Homebrew/utils/gems.rb | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/Library/Homebrew/utils/gems.rb b/Library/Homebrew/utils/gems.rb
index f3ca4f8f11..c2c7066d25 100644
--- a/Library/Homebrew/utils/gems.rb
+++ b/Library/Homebrew/utils/gems.rb
@@ -244,7 +244,12 @@ module Homebrew
     groups |= (user_gem_groups & valid_gem_groups)
     groups.sort!
 
-    ENV["BUNDLE_CACHE_PATH"] = (HOMEBREW_CACHE/"bundler_cache").to_s
+    homebrew_cache = if defined?(HOMEBREW_CACHE)
+      HOMEBREW_CACHE.to_s
+    else
+      ENV.fetch("HOMEBREW_CACHE")
+    end
+    ENV["BUNDLE_CACHE_PATH"] = "#{homebrew_cache}/bundler_cache"
     ENV["BUNDLE_GEMFILE"] = gemfile
     ENV["BUNDLE_WITH"] = groups.join(" ")
     ENV["BUNDLE_FROZEN"] = "true"