fix: raise InvalidEventException for incorrect Properties field usage for Api event type

samtranslator/plugins/api/implicit_http_api_plugin.py

@@ -58,7 +58,7 @@ def _process_api_events(
             # api_events only contains HttpApi events
             event_properties = event.get("Properties", {})
 
-            if event_properties and not isinstance(event_properties, dict):
+            if not isinstance(event_properties, dict):
                 raise InvalidEventException(
                     logicalId,
                     "Event 'Properties' must be an Object. If you're using YAML, this may be an indentation issue.",

tests/translator/input/error_function_api_invalid_properties.yaml

@@ -0,0 +1,21 @@
+Resources:
+  Function:
+    Type: AWS::Serverless::Function
+    Properties:
+      Runtime: python3.7
+      Handler: index.handler
+      CodeUri: s3://bucket/key
+      Events:
+        Api:
+          Type: HttpApi
+          Properties: ''
+  Function2:
+    Type: AWS::Serverless::Function
+    Properties:
+      Runtime: python3.7
+      Handler: index.handler
+      CodeUri: s3://bucket/key
+      Events:
+        Api2:
+          Type: RestApi
+          Properties: ''

tests/translator/output/error_function_api_invalid_properties.json

@@ -0,0 +1,3 @@
+{
+  "errorMessage": "Invalid Serverless Application Specification document. Number of errors found: 1. Resource with id [Function] is invalid. Event with id [Api] is invalid. Event 'Properties' must be an Object. If you're using YAML, this may be an indentation issue."
+}