Error raised from Flask app is logged as successful function execution

azure/functions/_http_wsgi.py

@@ -1,6 +1,5 @@
 # Copyright (c) Microsoft Corporation. All rights reserved.
 # Licensed under the MIT License.
-
 from typing import Dict, List, Optional, Any
 import logging
 from io import BytesIO, StringIO
@@ -192,13 +191,16 @@ def _handle(self, req, context):
         wsgi_request = WsgiRequest(req, context)
         environ = wsgi_request.to_environ(self._wsgi_error_buffer)
         wsgi_response = WsgiResponse.from_app(self._app, environ)
-        self._handle_errors()
+        self._handle_errors(wsgi_response)
         return wsgi_response.to_func_response()
 
-    def _handle_errors(self):
+    def _handle_errors(self, wsgi_response):
         if self._wsgi_error_buffer.tell() > 0:
             self._wsgi_error_buffer.seek(0)
             error_message = linesep.join(
                 self._wsgi_error_buffer.readline()
             )
             raise Exception(error_message)
+
+        if wsgi_response._status_code >= 500:
+            raise Exception(b''.join(wsgi_response._buffer))

tests/test_http_wsgi.py

@@ -4,6 +4,8 @@
 import unittest
 from io import StringIO, BytesIO
 
+import pytest
+
 import azure.functions as func
 from azure.functions._abc import TraceContext, RetryContext
 from azure.functions._http import HttpResponseHeaders
@@ -181,6 +183,20 @@ def main(req, context):
         self.assertEqual(func_response.status_code, 200)
         self.assertEqual(func_response.get_body(), b'sample string')
 
+    def test_middleware_handle_with_server_error_status_code(self):
+        """Test if the middleware can be used by exposing the .handle method,
+        specifically when the middleware is used as
+        def main(req, context):
+            return WsgiMiddleware(app).handle(req, context)
+        """
+        app = self._generate_wsgi_app(status="500 Internal Server Error",
+                                      response_body=b'internal server error')
+        func_request = self._generate_func_request()
+        with pytest.raises(Exception) as exec_info:
+            func_response = WsgiMiddleware(app).handle(func_request)
+            self.assertEqual(func_response.status_code, 500)
+        self.assertEqual(exec_info.value.args[0], b'internal server error')
+
     def test_middleware_wrapper(self):
         """Test if the middleware can be used by exposing the .main property,
         specifically when the middleware is used as