Add method for determining service availability in a region (#2321)

Author: marekaiv

samtranslator/plugins/application/serverless_app_plugin.py

@@ -111,7 +111,7 @@ def on_before_transform_template(self, template_dict):
 
             if key not in self._applications:
                 try:
-                    if not RegionConfiguration.is_sar_supported():
+                    if not RegionConfiguration.is_service_supported("serverlessrepo"):
                         raise InvalidResourceException(
                             logical_id, "Serverless Application Repository is not available in this region."
                         )

samtranslator/region_configuration.py

@@ -26,31 +26,32 @@ def is_apigw_edge_configuration_supported(cls):
         ]
 
     @classmethod
-    def is_sar_supported(cls):
+    def is_service_supported(cls, service, region=None):
         """
-        SAR is not supported in some regions.
+        Not all services are supported in all regions.  This method returns whether a given
+        service is supported in a given region.  If no region is specified, the current region
+        (as identified by boto3) is used.
         https://aws.amazon.com/about-aws/global-infrastructure/regional-product-services/
-        https://docs.aws.amazon.com/general/latest/gr/serverlessrepo.html
 
-        :return: True, if SAR is supported in current region.
+        :param service: service code (string used to obtain a boto3 client for the service)
+        :param region: region identifier (e.g., us-east-1)
+        :return: True, if the service is supported in the region
         """
 
         session = boto3.Session()
 
-        # get the current region
-        region = session.region_name
+        if not region:
+            # get the current region
+            region = session.region_name
 
-        # need to handle when region is None so that it won't break
-        if region is None:
-            if ArnGenerator.BOTO_SESSION_REGION_NAME is not None:
-                region = ArnGenerator.BOTO_SESSION_REGION_NAME
-            else:
-                raise NoRegionFound("AWS Region cannot be found")
+            # need to handle when region is None so that it won't break
+            if region is None:
+                if ArnGenerator.BOTO_SESSION_REGION_NAME is not None:
+                    region = ArnGenerator.BOTO_SESSION_REGION_NAME
+                else:
+                    raise NoRegionFound("AWS Region cannot be found")
 
-        # boto3 get_available_regions call won't return us-gov and cn regions even if SAR is available
-        if region.startswith("cn") or region.startswith("us-gov"):
-            return True
-
-        # get all regions where SAR are available
-        available_regions = session.get_available_regions("serverlessrepo")
+        # check if the service is available in region
+        partition = session.get_partition_for_region(region)
+        available_regions = session.get_available_regions(service, partition_name=partition)
         return region in available_regions

tests/unit/test_region_configuration.py

@@ -36,3 +36,27 @@ def test_when_apigw_edge_configuration_is_not_supported(self, partition):
             get_partition_name_patch.return_value = partition
 
             self.assertFalse(RegionConfiguration.is_apigw_edge_configuration_supported())
+
+    @parameterized.expand(
+        [
+            # use ec2 as it's just about everywhere
+            ["ec2", "cn-north-1"],
+            ["ec2", "us-west-2"],
+            ["ec2", "us-gov-east-1"],
+            ["ec2", "us-isob-east-1"],
+            ["ec2", None],
+            # test SAR since SAM uses that
+            ["serverlessrepo", "us-east-1"],
+            ["serverlessrepo", "ap-southeast-2"],
+        ]
+    )
+    def test_is_service_supported_positive(self, service, region):
+        self.assertTrue(RegionConfiguration.is_service_supported(service, region))
+
+    def test_is_service_supported_negative(self):
+        # use an unknown service name
+        self.assertFalse(RegionConfiguration.is_service_supported("ec1", "us-east-1"))
+        # use a region that does not exist
+        self.assertFalse(RegionConfiguration.is_service_supported("ec2", "us-east-0"))
+        # hard to test with a real service, since the test may start failing once that
+        # service is rolled out to more regions...