From 01eb9b2a97f47202daa4947b5dc1c7046065faa0 Mon Sep 17 00:00:00 2001
From: Jon Rowe <hello@jonrowe.co.uk>
Date: Mon, 26 Jun 2023 10:46:13 +0100
Subject: [PATCH] Make RSpec::Support.thread_local_data thread but not fiber
 local

---
 Changelog.md               |  5 +++++
 lib/rspec/support.rb       | 10 ++++++++--
 spec/rspec/support_spec.rb | 20 ++++++++++++++++++++
 3 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/Changelog.md b/Changelog.md
index 551af9cc..f99a3658 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -1,6 +1,11 @@
 ### Development
 [Full Changelog](http://github.com/rspec/rspec-support/compare/v3.12.0...main)
 
+Bug Fixes:
+
+* Fix `RSpec::Support.thread_local_data` to be Thread local but not Fiber local.
+  (Jon Rowe, #581)
+
 ### 3.12.0 / 2022-10-26
 [Full Changelog](http://github.com/rspec/rspec-support/compare/v3.11.1...v3.12.0)
 Enhancements:
diff --git a/lib/rspec/support.rb b/lib/rspec/support.rb
index b85eae3c..4732f728 100644
--- a/lib/rspec/support.rb
+++ b/lib/rspec/support.rb
@@ -89,8 +89,14 @@ def self.class_of(object)
     end
 
     # A single thread local variable so we don't excessively pollute that namespace.
-    def self.thread_local_data
-      Thread.current[:__rspec] ||= {}
+    if RUBY_VERSION.to_f >= 2
+      def self.thread_local_data
+        Thread.current.thread_variable_get(:__rspec) || Thread.current.thread_variable_set(:__rspec, {})
+      end
+    else
+      def self.thread_local_data
+        Thread.current[:__rspec] ||= {}
+      end
     end
 
     # @api private
diff --git a/spec/rspec/support_spec.rb b/spec/rspec/support_spec.rb
index 2bb28351..75d784dd 100644
--- a/spec/rspec/support_spec.rb
+++ b/spec/rspec/support_spec.rb
@@ -186,6 +186,26 @@ def object.some_method
       end
     end
 
+    describe ".thread_local_data" do
+      it "contains data local to the current thread" do
+        RSpec::Support.thread_local_data[:__for_test] = :oh_hai
+
+        Thread.new do
+          expect(RSpec::Support.thread_local_data).to eq({})
+        end.join
+      end
+
+      if defined?(Fiber) && RUBY_VERSION.to_f >= 2.0
+        it "shares data across fibres" do
+          RSpec::Support.thread_local_data[:__for_test] = :oh_hai
+
+          Fiber.new do
+            expect(RSpec::Support.thread_local_data[:__for_test]).to eq(:oh_hai)
+          end.resume
+        end
+      end
+    end
+
     describe "failure notification" do
       before { @failure_notifier = RSpec::Support.failure_notifier }
       after  { RSpec::Support.failure_notifier = @failure_notifier }