Use a null object with RequestStore

Makes it easier and safer to use RequestStore because you don't need to
check `RequestStore.active?` before using it. You just have to use
`Gitlab::SafeRequestStore` instead.

2 files changed, 64 insertions, 0 deletions

diff --git a/lib/gitlab/null_request_store.rb b/lib/gitlab/null_request_store.rb
new file mode 100644
index 00000000000..8db331dcb9f
--- /dev/null
+++ b/lib/gitlab/null_request_store.rb
@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+
+# Used by Gitlab::SafeRequestStore
+module Gitlab
+  # The methods `begin!`, `clear!`, and `end!` are not defined because they
+  # should only be called directly on `RequestStore`.
+  class NullRequestStore
+    def store
+      {}
+    end
+
+    def active?
+    end
+
+    def read(key)
+    end
+
+    def [](key)
+    end
+
+    def write(key, value)
+      value
+    end
+
+    def []=(key, value)
+      value
+    end
+
+    def exist?(key)
+      false
+    end
+
+    def fetch(key, &block)
+      yield
+    end
+
+    def delete(key, &block)
+      yield(key) if block_given?
+    end
+  end
+end
diff --git a/lib/gitlab/safe_request_store.rb b/lib/gitlab/safe_request_store.rb
new file mode 100644
index 00000000000..4e82353adb6
--- /dev/null
+++ b/lib/gitlab/safe_request_store.rb
@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module SafeRequestStore
+    NULL_STORE = Gitlab::NullRequestStore.new
+
+    class << self
+      # These methods should always run directly against RequestStore
+      delegate :clear!, :begin!, :end!, :active?, to: :RequestStore
+
+      # These methods will run against NullRequestStore if RequestStore is disabled
+      delegate :read, :[], :write, :[]=, :exist?, :fetch, :delete, to: :store
+    end
+
+    def self.store
+      if RequestStore.active?
+        RequestStore
+      else
+        NULL_STORE
+      end
+    end
+  end
+end