fix: Update validation for dead letter queue (#2324)

Author: jonife

samtranslator/model/sam_resources.py

@@ -593,6 +593,12 @@ def _validate_dlq(self):
                 "'DeadLetterQueue' requires Type and TargetArn properties to be specified.".format(valid_dlq_types),
             )
 
+        if not (isinstance(self.DeadLetterQueue.get("Type"), str)):
+            raise InvalidResourceException(
+                self.logical_id,
+                "'DeadLetterQueue' property 'Type' should be of type str.",
+            )
+
         # Validate required Types
         if not self.DeadLetterQueue["Type"] in self.dead_letter_queue_policy_actions:
             raise InvalidResourceException(

tests/translator/input/error_function_with_invalid_dlq_property_type.yaml

@@ -0,0 +1,17 @@
+Transform: "AWS::Serverless-2016-10-31"
+Parameter:
+  DeadLetterQueueType:
+    Type: String
+    Default: SQS
+
+Resources:
+  MySqsDlqLambdaFunction:
+    Type: AWS::Serverless::Function
+    Properties:
+      Handler: index.handler
+      Runtime: python2.7
+      CodeUri: s3://sam-demo-bucket/hello.zip
+      DeadLetterQueue:
+        Type:
+          Ref: DeadLetterQueueType
+        TargetArn: arn

tests/translator/output/error_function_with_invalid_dlq_property_type.json

@@ -0,0 +1,8 @@
+{
+  "errors": [
+    {
+      "errorMessage": "Invalid Serverless Application Specification document. Number of errors found: 1. Resource with id [MySqsDlqLambdaFunction] is invalid. 'DeadLetterQueue' property 'Type' should be of type str."
+    }
+  ],
+  "errorMessage": "Invalid Serverless Application Specification document. Number of errors found: 1. Resource with id [MySqsDlqLambdaFunction] is invalid. 'DeadLetterQueue' property 'Type' should be of type str."
+}