Ensure that each thread has its own client

.rubocop_todo.yml

@@ -1,6 +1,6 @@
 # This configuration was generated by
 # `rubocop --auto-gen-config`
-# on 2017-09-27 21:19:01 +0200 using RuboCop version 0.50.0.
+# on 2017-10-12 18:19:29 +0200 using RuboCop version 0.50.0.
 # The point is for the user to remove these configuration records
 # one by one as the offenses are removed from the code base.
 # Note that changes in the inspected code, or installation of new
@@ -10,46 +10,44 @@
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   Max: 49
 
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 # Configuration parameters: CountComments.
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+  Max: 583
 
 # Offense count: 8
 Metrics/CyclomaticComplexity:
   Max: 13
 
-# Offense count: 216
+# Offense count: 215
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 # URISchemes: http, https
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 Metrics/ParameterLists:
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-# Offense count: 5
+# Offense count: 4
 Metrics/PerceivedComplexity:
-  Max: 11
-  Exclude:
-    - 'lib/stripe/stripe_object.rb'
+  Max: 15
 
 # Offense count: 2
 Style/ClassVars:

lib/stripe/stripe_client.rb

@@ -17,7 +17,7 @@ def self.active_client
     end
 
     def self.default_client
-      @default_client ||= StripeClient.new(default_conn)
+      Thread.current[:stripe_client_default_client] ||= StripeClient.new(default_conn)
     end
 
     # A default Faraday connection to be used when one isn't configured. This

test/stripe/stripe_client_test.rb

@@ -19,6 +19,15 @@ class StripeClientTest < Test::Unit::TestCase
       should "be a StripeClient" do
         assert_kind_of StripeClient, StripeClient.default_client
       end
+
+      should "be a different client on each thread" do
+        other_thread_client = nil
+        thread = Thread.new do
+          other_thread_client = StripeClient.default_client
+        end
+        thread.join
+        refute_equal StripeClient.default_client, other_thread_client
+      end
     end
 
     context ".default_conn" do