From e1ffd6a271e352a725aa0394b654e9250f2d8240 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?R=C3=A9my=20Coutable?= <remy@rymai.me>
Date: Thu, 31 May 2018 18:12:48 +0200
Subject: [PATCH] Use RequestStore to memoize Flipper features so that memoized
 values are cleared between requests
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Signed-off-by: Rémy Coutable <remy@rymai.me>
---
 lib/feature.rb           | 11 +++++++++--
 spec/lib/feature_spec.rb | 24 ++++++++++++++++++++++++
 2 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/lib/feature.rb b/lib/feature.rb
index 6474de6e56d..314ae224d90 100644
--- a/lib/feature.rb
+++ b/lib/feature.rb
@@ -63,8 +63,15 @@ class Feature
     end
 
     def flipper
-      Thread.current[:flipper] ||=
-        Flipper.new(flipper_adapter).tap { |flip| flip.memoize = true }
+      if RequestStore.active?
+        RequestStore[:flipper] ||= build_flipper_instance
+      else
+        @flipper ||= build_flipper_instance
+      end
+    end
+
+    def build_flipper_instance
+      Flipper.new(flipper_adapter).tap { |flip| flip.memoize = true }
     end
 
     # This method is called from config/initializers/flipper.rb and can be used
diff --git a/spec/lib/feature_spec.rb b/spec/lib/feature_spec.rb
index 10020511bf8..6eb10497428 100644
--- a/spec/lib/feature_spec.rb
+++ b/spec/lib/feature_spec.rb
@@ -64,4 +64,28 @@ describe Feature do
       expect(described_class.all).to eq(features.to_a)
     end
   end
+
+  describe '.flipper' do
+    shared_examples 'a memoized Flipper instance' do
+      it 'memoizes the Flipper instance' do
+        expect(Flipper).to receive(:new).once.and_call_original
+
+        2.times do
+          described_class.flipper
+        end
+      end
+    end
+
+    context 'when request store is inactive' do
+      before do
+        described_class.instance_variable_set(:@flipper, nil)
+      end
+
+      it_behaves_like 'a memoized Flipper instance'
+    end
+
+    context 'when request store is inactive', :request_store do
+      it_behaves_like 'a memoized Flipper instance'
+    end
+  end
 end