From c50847cabfd6c8506ec87649e13202af5d6af3e2 Mon Sep 17 00:00:00 2001
From: Christopher Grebs <cg@webshox.org>
Date: Fri, 26 Jul 2019 16:28:44 +0200
Subject: [PATCH 1/3] Handle 'None' return value of wait() properly during
 throttling.

Fixes #6836
---
 rest_framework/views.py  | 12 +++++++++++-
 tests/test_throttling.py | 20 ++++++++++++++++++++
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/rest_framework/views.py b/rest_framework/views.py
index 832f172330..5f52adaa51 100644
--- a/rest_framework/views.py
+++ b/rest_framework/views.py
@@ -356,7 +356,17 @@ def check_throttles(self, request):
                 throttle_durations.append(throttle.wait())
 
         if throttle_durations:
-            self.throttled(request, max(throttle_durations))
+            # Filter out `None` values which may happen in case of config / rate
+            # changes, see #1438
+            durations = [
+                duration for duration in throttle_durations
+                if duration is not None
+            ]
+
+            if durations:
+                self.throttled(request, max(durations))
+            else:
+                self.throttled(request, None)
 
     def determine_version(self, request, *args, **kwargs):
         """
diff --git a/tests/test_throttling.py b/tests/test_throttling.py
index 3c172e2636..2cc60a1a7a 100644
--- a/tests/test_throttling.py
+++ b/tests/test_throttling.py
@@ -159,6 +159,26 @@ def test_request_throttling_multiple_throttles(self):
         assert response.status_code == 429
         assert int(response['retry-after']) == 58
 
+    def test_handle_negative_throttle_value(self):
+        self.set_throttle_timer(MockView_DoubleThrottling, 0)
+        request = self.factory.get('/')
+        for dummy in range(24):
+            response = MockView_DoubleThrottling.as_view()(request)
+        assert response.status_code == 429
+        assert int(response['retry-after']) == 60
+
+        previous_rate = User3SecRateThrottle.rate
+        User3SecRateThrottle.rate = '1/sec'
+
+        for dummy in range(24):
+            response = MockView_DoubleThrottling.as_view()(request)
+
+        assert response.status_code == 429
+        assert int(response['retry-after']) == 60
+
+        # reset
+        User3SecRateThrottle.rate = previous_rate
+
     def ensure_response_header_contains_proper_throttle_field(self, view, expected_headers):
         """
         Ensure the response returns an Retry-After field with status and next attributes

From 957b39fa8d6ff0f9866d0f697c4ff93a343613b7 Mon Sep 17 00:00:00 2001
From: Christopher Grebs <cg@webshox.org>
Date: Tue, 30 Jul 2019 09:40:32 +0200
Subject: [PATCH 2/3] Wrap test in try/finally, cleanup duration determination

---
 rest_framework/views.py  |  6 ++----
 tests/test_throttling.py | 17 +++++++++--------
 2 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/rest_framework/views.py b/rest_framework/views.py
index 5f52adaa51..da85cccec8 100644
--- a/rest_framework/views.py
+++ b/rest_framework/views.py
@@ -363,10 +363,8 @@ def check_throttles(self, request):
                 if duration is not None
             ]
 
-            if durations:
-                self.throttled(request, max(durations))
-            else:
-                self.throttled(request, None)
+            duration = max(durations) if durations else None
+            self.throttled(request, duration)
 
     def determine_version(self, request, *args, **kwargs):
         """
diff --git a/tests/test_throttling.py b/tests/test_throttling.py
index 2cc60a1a7a..eb34a6c913 100644
--- a/tests/test_throttling.py
+++ b/tests/test_throttling.py
@@ -168,16 +168,17 @@ def test_handle_negative_throttle_value(self):
         assert int(response['retry-after']) == 60
 
         previous_rate = User3SecRateThrottle.rate
-        User3SecRateThrottle.rate = '1/sec'
+        try:
+            User3SecRateThrottle.rate = '1/sec'
 
-        for dummy in range(24):
-            response = MockView_DoubleThrottling.as_view()(request)
-
-        assert response.status_code == 429
-        assert int(response['retry-after']) == 60
+            for dummy in range(24):
+                response = MockView_DoubleThrottling.as_view()(request)
 
-        # reset
-        User3SecRateThrottle.rate = previous_rate
+            assert response.status_code == 429
+            assert int(response['retry-after']) == 60
+        finally:
+            # reset
+            User3SecRateThrottle.rate = previous_rate
 
     def ensure_response_header_contains_proper_throttle_field(self, view, expected_headers):
         """

From 8e6ee98ee921ea2f7a3d94dc99e54a9617483831 Mon Sep 17 00:00:00 2001
From: Christopher Grebs <cg@webshox.org>
Date: Wed, 7 Aug 2019 10:48:15 +0200
Subject: [PATCH 3/3] Use default argument of max() and change test name

---
 rest_framework/views.py  | 2 +-
 tests/test_throttling.py | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/rest_framework/views.py b/rest_framework/views.py
index da85cccec8..bec10560a9 100644
--- a/rest_framework/views.py
+++ b/rest_framework/views.py
@@ -363,7 +363,7 @@ def check_throttles(self, request):
                 if duration is not None
             ]
 
-            duration = max(durations) if durations else None
+            duration = max(durations, default=None)
             self.throttled(request, duration)
 
     def determine_version(self, request, *args, **kwargs):
diff --git a/tests/test_throttling.py b/tests/test_throttling.py
index eb34a6c913..d5a61232d9 100644
--- a/tests/test_throttling.py
+++ b/tests/test_throttling.py
@@ -159,7 +159,7 @@ def test_request_throttling_multiple_throttles(self):
         assert response.status_code == 429
         assert int(response['retry-after']) == 58
 
-    def test_handle_negative_throttle_value(self):
+    def test_throttle_rate_change_negative(self):
         self.set_throttle_timer(MockView_DoubleThrottling, 0)
         request = self.factory.get('/')
         for dummy in range(24):