feat: add support for using 'AWS::Region' in Ref and Sub (#855)

Author: honglu

samtranslator/intrinsics/actions.py

@@ -371,7 +371,7 @@ def handler_method(full_ref, ref_value):
         """
 
         # RegExp to find pattern "${logicalId.property}" and return the word inside bracket
-        logical_id_regex = '[A-Za-z0-9\.]+'
+        logical_id_regex = '[A-Za-z0-9\.]+|AWS::[A-Z][A-Za-z]*'
         ref_pattern = re.compile(r'\$\{(' + logical_id_regex + ')\}')
 
         # Find all the pattern, and call the handler to decide how to substitute them.

samtranslator/translator/translator.py

@@ -1,4 +1,5 @@
 import copy
+import boto3
 
 from samtranslator.model import ResourceTypeResolver, sam_resources
 from samtranslator.translator.verify_logical_id import verify_unique_logical_id
@@ -48,6 +49,7 @@ def translate(self, sam_template, parameter_values):
         # Create & Install plugins
         sam_plugins = prepare_plugins(self.plugins)
         parameter_values = self._add_default_parameter_values(sam_template, parameter_values)
+        parameter_values = self._add_pseudo_parameter_values(parameter_values)
 
         self.sam_parser.parse(
             sam_template=sam_template,
@@ -205,6 +207,12 @@ def _add_default_parameter_values(self, sam_template, parameter_values):
 
         return default_values
 
+    def _add_pseudo_parameter_values(self, parameter_values):
+        updated_parameter_values = copy.deepcopy(parameter_values)
+        if 'AWS::Region' not in updated_parameter_values:
+            updated_parameter_values['AWS::Region'] = boto3.session.Session().region_name
+        return updated_parameter_values
+
 
 def prepare_plugins(plugins):
     """

tests/intrinsics/test_actions.py

@@ -419,6 +419,23 @@ def test_sub_all_refs_with_dict_input(self):
 
         self.assertEqual(expected, result)
 
+    def test_sub_all_refs_with_pseudo_parameters(self):
+        parameters = {
+            "key1": "value1",
+            "AWS::Region": "ap-southeast-1"
+        }
+        input = {
+            "Fn::Sub": "hello ${AWS::Region} ${key1}"
+        }
+        expected = {
+            "Fn::Sub": "hello ap-southeast-1 value1"
+        }
+
+        sub = SubAction()
+        result = sub.resolve_parameter_refs(input, parameters)
+
+        self.assertEqual(expected, result)
+
 class TestSubInternalMethods(TestCase):
 
     @patch.object(SubAction, "_sub_all_refs")

tests/translator/input/layers_with_intrinsics.yaml

@@ -34,3 +34,15 @@ Resources:
       ContentUri: s3://sam-demo-bucket/layer.zip
       LayerName: !Sub layer-${LayerNameParam}
 
+  LayerWithRefNameIntrinsicRegion:
+    Type: AWS::Serverless::LayerVersion
+    Properties:
+      ContentUri: s3://sam-demo-bucket/layer.zip
+      LayerName: !Ref 'AWS::Region'
+
+  LayerWithSubNameIntrinsicRegion:
+    Type: AWS::Serverless::LayerVersion
+    Properties:
+      ContentUri: s3://sam-demo-bucket/layer.zip
+      LayerName: !Sub 'layer-${AWS::Region}'
+

tests/translator/output/aws-cn/layers_with_intrinsics.json

@@ -24,6 +24,30 @@
         "LayerName": "SomeLayerName"
       }
     },
+    "LayerWithRefNameIntrinsicRegion186db7e435": {
+      "DeletionPolicy": "Retain",
+      "Type": "AWS::Lambda::LayerVersion",
+      "Properties": {
+        "Content": {
+          "S3Bucket": "sam-demo-bucket",
+          "S3Key": "layer.zip"
+        },
+        "LayerName": "cn-north-1"
+      }
+    },
+    "LayerWithSubNameIntrinsicRegionfbc3f9f13d": {
+      "DeletionPolicy": "Retain",
+      "Type": "AWS::Lambda::LayerVersion",
+      "Properties": {
+        "Content": {
+          "S3Bucket": "sam-demo-bucket",
+          "S3Key": "layer.zip"
+        },
+        "LayerName": {
+          "Fn::Sub": "layer-cn-north-1"
+        }
+      }
+    },
     "LayerWithRuntimesIntrinsic1a006faa85": {
       "DeletionPolicy": "Retain",
       "Type": "AWS::Lambda::LayerVersion",

tests/translator/output/aws-us-gov/layers_with_intrinsics.json

@@ -24,6 +24,30 @@
         "LayerName": "SomeLayerName"
       }
     },
+    "LayerWithRefNameIntrinsicRegionad31c93c8b": {
+      "DeletionPolicy": "Retain",
+      "Type": "AWS::Lambda::LayerVersion",
+      "Properties": {
+        "Content": {
+          "S3Bucket": "sam-demo-bucket",
+          "S3Key": "layer.zip"
+        },
+        "LayerName": "us-gov-west-1"
+      }
+    },
+    "LayerWithSubNameIntrinsicRegion5b2c74d55e": {
+      "DeletionPolicy": "Retain",
+      "Type": "AWS::Lambda::LayerVersion",
+      "Properties": {
+        "Content": {
+          "S3Bucket": "sam-demo-bucket",
+          "S3Key": "layer.zip"
+        },
+        "LayerName": {
+          "Fn::Sub": "layer-us-gov-west-1"
+        }
+      }
+    },
     "LayerWithRuntimesIntrinsic1a006faa85": {
       "DeletionPolicy": "Retain",
       "Type": "AWS::Lambda::LayerVersion",

tests/translator/output/layers_with_intrinsics.json

@@ -24,6 +24,30 @@
         "LayerName": "SomeLayerName"
       }
     },
+    "LayerWithRefNameIntrinsicRegion32bf7198a5": {
+      "DeletionPolicy": "Retain",
+      "Type": "AWS::Lambda::LayerVersion",
+      "Properties": {
+        "Content": {
+          "S3Bucket": "sam-demo-bucket",
+          "S3Key": "layer.zip"
+        },
+        "LayerName": "ap-southeast-1"
+      }
+    },
+    "LayerWithSubNameIntrinsicRegiond71326de24": {
+      "DeletionPolicy": "Retain",
+      "Type": "AWS::Lambda::LayerVersion",
+      "Properties": {
+        "Content": {
+          "S3Bucket": "sam-demo-bucket",
+          "S3Key": "layer.zip"
+        },
+        "LayerName": {
+          "Fn::Sub": "layer-ap-southeast-1"
+        }
+      }
+    },
     "LayerWithRuntimesIntrinsic1a006faa85": {
       "DeletionPolicy": "Retain",
       "Type": "AWS::Lambda::LayerVersion",

tests/translator/test_translator.py

@@ -731,6 +731,39 @@ def test_add_default_parameter_values_must_ignore_invalid_template_parameters(se
             sam_template, parameter_values)
         self.assertEqual(expected, result)
 
+    @patch('boto3.session.Session.region_name', 'ap-southeast-1')
+    def test_add_pseudo_parameter_values_aws_region(self):
+        parameter_values = {
+            "Param1": "value1"
+        }
+
+        expected = {
+            "Param1": "value1",
+            "AWS::Region": "ap-southeast-1"
+        }
+
+
+        sam_parser = Parser()
+        translator = Translator({}, sam_parser)
+        result = translator._add_pseudo_parameter_values(parameter_values)
+        self.assertEqual(expected, result)
+
+    @patch('boto3.session.Session.region_name', 'ap-southeast-1')
+    def test_add_pseudo_parameter_values_aws_region_not_override(self):
+        parameter_values = {
+            "AWS::Region": "value1"
+        }
+
+        expected = {
+            "AWS::Region": "value1"
+        }
+
+
+        sam_parser = Parser()
+        translator = Translator({}, sam_parser)
+        result = translator._add_pseudo_parameter_values(parameter_values)
+        self.assertEqual(expected, result)
+
 
 class TestTemplateValidation(TestCase):