Improve exception processing for Route53 with invalid type

samtranslator/model/api/api_generator.py

@@ -515,6 +515,12 @@ def _construct_api_domain(self, rest_api):
         record_set_group = None
         if self.domain.get("Route53") is not None:
             route53 = self.domain.get("Route53")
+            if not isinstance(route53, dict):
+                raise InvalidResourceException(
+                    self.logical_id,
+                    "Invalid property type '{}' for Route53. "
+                    "Expected a map defines an Amazon Route 53 configuration'.".format(type(route53).__name__),
+                )
             if route53.get("HostedZoneId") is None and route53.get("HostedZoneName") is None:
                 raise InvalidResourceException(
                     self.logical_id,

tests/translator/input/error_api_with_custom_domains_route53_invalid_type.yaml

@@ -0,0 +1,33 @@
+Resources:
+  MyFunction:
+    Type: AWS::Serverless::Function
+    Properties:
+      InlineCode: |
+        exports.handler = async (event) => {
+          const response = {
+            statusCode: 200,
+            body: JSON.stringify('Hello from Lambda!'),
+          };
+          return response;
+        };
+      Handler: index.handler
+      Runtime: nodejs12.x
+      Events:
+        Api:
+          Type: Api
+          Properties:
+            RestApiId: !Ref MyApi
+            Method: Put
+            Path: /get
+
+  MyApi:
+    Type: AWS::Serverless::Api
+    Properties:
+      OpenApiVersion: 3.0.1
+      StageName: Prod
+      Domain:
+        DomainName: 'api-example.com'
+        CertificateArn: 'my-api-cert-arn'
+        EndpointConfiguration: 'EDGE'
+        BasePath: [ "/get"]
+        Route53: 'InvalidString'

tests/translator/output/error_api_with_custom_domains_route53_invalid_type.json

@@ -0,0 +1,8 @@
+{
+  "errors": [
+    {
+      "errorMessage": "Resource with id [MyApi] is invalid. Invalid property type 'Py27UniStr' for Route53. Expected a map defines an Amazon Route 53 configuration'."
+    }
+  ],
+  "errorMessage": "Invalid Serverless Application Specification document. Number of errors found: 1. Resource with id [MyApi] is invalid. Invalid property type 'Py27UniStr' for Route53. Expected a map defines an Amazon Route 53 configuration'."
+}