Update region override for no region given case

botocore/endpoint.py

@@ -294,27 +294,28 @@ def create_endpoint(self, service_model, region_name=None, is_secure=True,
                 raise
         # We only support the credentialScope.region in the properties
         # bag right now, so if it's available, it will override the
-        # provided region name if an endpoint url was not manually set.
-        # If a endpoint url was specified, the user must specify a region.
-        region_name_override = None
-        if endpoint_url is None:
-            region_name_override = endpoint['properties'].get(
-                'credentialScope', {}).get('region')
+        # provided region name.
+        region_name_override = endpoint['properties'].get(
+            'credentialScope', {}).get('region')
         if signature_version is NOT_SET:
             signature_version = service_model.signature_version
             if 'signatureVersion' in endpoint['properties']:
                 signature_version = endpoint['properties']['signatureVersion']
-        if region_name_override is not None:
-            # Letting the heuristics rule override the region_name
-            # allows for having a default region of something like us-west-2
-            # for IAM, but we still will know to use us-east-1 for sigv4.
-            region_name = region_name_override
         if endpoint_url is not None:
+            # If an endpoint_url is provided, do not use region name override if a region
+            # was provided by the user.
+            if region_name is not None:
+                region_name_override = None
             # If the user provides an endpoint url, we'll use that
             # instead of what the heuristics rule gives us.
             final_endpoint_url = endpoint_url
         else:
             final_endpoint_url = endpoint['uri']
+        if region_name_override is not None:
+            # Letting the heuristics rule override the region_name
+            # allows for having a default region of something like us-west-2
+            # for IAM, but we still will know to use us-east-1 for sigv4.
+            region_name = region_name_override
         return self._get_endpoint(service_model, region_name,
                                   signature_version, final_endpoint_url,
                                   verify, response_parser_factory)

tests/unit/test_endpoint.py

@@ -339,6 +339,23 @@ def test_endpoint_resolver_no_uses_credential_scope_with_endpoint_url(self):
         endpoint = creator.create_endpoint(self.service_model, endpoint_url='https://foo')
         self.assertEqual(endpoint.region_name, 'us-west-2')
 
+    def test_endpoint_resolver_uses_credential_scope_with_endpoint_url_and_no_region(self):
+        resolver = Mock()
+        resolver_region_override = 'us-east-1'
+        resolver.construct_endpoint.return_value = {
+            'uri': 'https://endpoint.url',
+            'properties': {
+                'credentialScope': {
+                    'region': resolver_region_override,
+                }
+            }
+        }
+        original_region_name = None
+        creator = EndpointCreator(resolver, original_region_name,
+                                  Mock(), 'user-agent')
+        endpoint = creator.create_endpoint(self.service_model, endpoint_url='https://foo')
+        self.assertEqual(endpoint.region_name, resolver_region_override)
+
 
 class TestAWSSession(unittest.TestCase):
     def test_auth_header_preserved_from_s3_redirects(self):