From 94b28dc7267693cbd1aa11dd4294409d6fea0051 Mon Sep 17 00:00:00 2001
From: Russell Keith-Magee <russell@keith-magee.com>
Date: Wed, 21 Dec 2016 13:27:23 +0800
Subject: [PATCH] Added protection against creating duplicate customers.

---
 pinax/stripe/actions/customers.py  | 20 +++++++++++++++-----
 pinax/stripe/tests/test_actions.py | 30 ++++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+), 5 deletions(-)

diff --git a/pinax/stripe/actions/customers.py b/pinax/stripe/actions/customers.py
index 73ca66c2d..5899a2d78 100644
--- a/pinax/stripe/actions/customers.py
+++ b/pinax/stripe/actions/customers.py
@@ -1,3 +1,4 @@
+from django.db import IntegrityError, transaction
 from django.utils import timezone
 from django.utils.encoding import smart_str
 
@@ -28,7 +29,9 @@ def can_charge(customer):
 
 def create(user, card=None, plan=settings.PINAX_STRIPE_DEFAULT_PLAN, charge_immediately=True):
     """
-    Creates a Stripe customer
+    Creates a Stripe customer.
+
+    If a customer already exists, the existing customer will be returned.
 
     Args:
         user: a user object
@@ -48,10 +51,17 @@ def create(user, card=None, plan=settings.PINAX_STRIPE_DEFAULT_PLAN, charge_imme
         plan=plan,
         trial_end=trial_end
     )
-    cus = models.Customer.objects.create(
-        user=user,
-        stripe_id=stripe_customer["id"]
-    )
+    try:
+        with transaction.atomic():
+            cus = models.Customer.objects.create(
+                user=user,
+                stripe_id=stripe_customer["id"]
+            )
+    except IntegrityError:
+        # There is already a Customer object for this user
+        stripe.Customer.retrieve(stripe_customer["id"]).delete()
+        return models.Customer.objects.get(user=user)
+
     sync_customer(cus, stripe_customer)
 
     if plan and charge_immediately:
diff --git a/pinax/stripe/tests/test_actions.py b/pinax/stripe/tests/test_actions.py
index f0022e84b..c5109cfd6 100644
--- a/pinax/stripe/tests/test_actions.py
+++ b/pinax/stripe/tests/test_actions.py
@@ -139,6 +139,36 @@ def test_customer_create_user_only(self, CreateMock, SyncMock):
         self.assertIsNone(kwargs["trial_end"])
         self.assertTrue(SyncMock.called)
 
+    @patch("stripe.Customer.retrieve")
+    @patch("stripe.Customer.create")
+    def test_customer_create_user_duplicate(self, CreateMock, RetrieveMock):
+        # Create an existing database customer for this user
+        original = Customer.objects.create(user=self.user, stripe_id='cus_XXXXX')
+
+        new_customer = Mock()
+        RetrieveMock.return_value = new_customer
+
+        # customers.Create will return a new customer instance
+        CreateMock.return_value = dict(id="cus_YYYYY")
+        customer = customers.create(self.user)
+
+        # But only one customer will exist - the original one
+        self.assertEqual(Customer.objects.count(), 1)
+        self.assertEqual(customer.stripe_id, original.stripe_id)
+
+        # Check that the customer hasn't been modified
+        self.assertEqual(customer.user, self.user)
+        self.assertEqual(customer.stripe_id, "cus_XXXXX")
+        _, kwargs = CreateMock.call_args
+        self.assertEqual(kwargs["email"], self.user.email)
+        self.assertIsNone(kwargs["source"])
+        self.assertIsNone(kwargs["plan"])
+        self.assertIsNone(kwargs["trial_end"])
+
+        # But a customer *was* created, retrieved, and then disposed of.
+        RetrieveMock.assert_called_once_with("cus_YYYYY")
+        new_customer.delete.assert_called_once()
+
     @patch("pinax.stripe.actions.invoices.create_and_pay")
     @patch("pinax.stripe.actions.customers.sync_customer")
     @patch("stripe.Customer.create")