Add context manager for translating Moto exceptions (#13129)

viren-nadkarni · web-flow · commit 515c19b30f75 · 2025-09-12T14:24:04.000+05:30
diff --git a/localstack-core/localstack/services/moto.py b/localstack-core/localstack/services/moto.py
@@ -1,15 +1,16 @@
 """
-This module provides tools to call moto using moto and botocore internals without going through the moto HTTP server.
+This module provides tools to call Moto service implementations.
 """
 
 import copy
 import sys
 from collections.abc import Callable
+from contextlib import AbstractContextManager
 from functools import lru_cache
 
 import moto.backends as moto_backends
 from moto.core.base_backend import BackendDict
-from moto.core.exceptions import RESTError
+from moto.core.exceptions import RESTError, ServiceException
 from rolo.router import RegexConverter
 from werkzeug.exceptions import NotFound
 from werkzeug.routing import Map, Rule
@@ -209,3 +210,38 @@ class _PartIsolatingRegexConverter(RegexConverter):
 
     def __init__(self, *args, **kwargs) -> None:
         super().__init__(*args, **kwargs)
+
+
+class ServiceExceptionTranslator(AbstractContextManager):
+    """
+    This reentrant context manager translates Moto exceptions into ASF service exceptions. This allows ASF to properly
+    serialise and generate the correct error response.
+
+    This is useful when invoking Moto operations directly by importing the backend. For example:
+
+        from moto.ses import ses_backends
+
+        backend = ses_backend['000000000000']['us-east-1']
+
+        with ServiceExceptionTranslator():
+            message = backend.send_raw_email(...)
+
+    If `send_raw_email(...)` raises any `moto.core.exceptions.ServiceException`, this context manager will transparently
+    generate and raise a `localstack.aws.api.core.CommonServiceException`, maintaining the error code and message.
+
+    This only works for Moto services that are integrated with its new core AWS response serialiser.
+    """
+
+    def __enter__(self):
+        pass
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        if exc_type is not None and issubclass(exc_type, ServiceException):
+            raise CommonServiceException(
+                code=exc_val.code,
+                message=exc_val.message,
+            )
+        return False
+
+
+translate_service_exception = ServiceExceptionTranslator()
diff --git a/localstack-core/localstack/services/ses/provider.py b/localstack-core/localstack/services/ses/provider.py
@@ -60,7 +60,7 @@
 from localstack.aws.connect import connect_to
 from localstack.constants import INTERNAL_AWS_SECRET_ACCESS_KEY
 from localstack.http import Resource, Response
-from localstack.services.moto import call_moto
+from localstack.services.moto import call_moto, translate_service_exception
 from localstack.services.plugins import ServiceLifecycleHook
 from localstack.services.ses.models import EmailType, SentEmail, SentEmailBody
 from localstack.utils.aws import arns
@@ -478,7 +478,8 @@ def send_raw_email(
         destinations = destinations or []
 
         backend = get_ses_backend(context)
-        message = backend.send_raw_email(source, destinations, raw_data)
+        with translate_service_exception:
+            message = backend.send_raw_email(source, destinations, raw_data)
 
         if event_destinations := backend.config_set_event_destination.get(configuration_set_name):
             payload = EventDestinationPayload(
diff --git a/tests/aws/services/ses/test_ses.py b/tests/aws/services/ses/test_ses.py
@@ -1122,3 +1122,13 @@ def test_send_templated_email_can_retrospect(self, create_template, aws_client):
 
         assert requests.delete("http://localhost:4566/_aws/ses").status_code == 204
         assert requests.get("http://localhost:4566/_aws/ses").json() == {"messages": []}
+
+    @markers.aws.validated
+    def test_send_email_raises_message_rejected(self, aws_client):
+        raw_message_data = "From: origin@example.com\nTo: destination@example.com\nSubject: test\n\nThis is the message body.\n\n"
+
+        with pytest.raises(ClientError) as exc:
+            aws_client.ses.send_raw_email(
+                Destinations=["invalid@example.com"], RawMessage={"Data": raw_message_data}
+            )
+        assert exc.value.response["Error"]["Code"] == "MessageRejected"
diff --git a/tests/aws/services/ses/test_ses.validation.json b/tests/aws/services/ses/test_ses.validation.json
@@ -70,5 +70,14 @@
   },
   "tests/aws/services/ses/test_ses.py::TestSES::test_trying_to_delete_event_destination_from_non_existent_configuration_set": {
     "last_validated_date": "2023-08-25T22:05:02+00:00"
+  },
+  "tests/aws/services/ses/test_ses.py::TestSESRetrospection::test_send_email_raises_message_rejected": {
+    "last_validated_date": "2025-09-11T11:03:52+00:00",
+    "durations_in_seconds": {
+      "setup": 0.0,
+      "call": 1.62,
+      "teardown": 0.0,
+      "total": 1.62
+    }
   }
 }
diff --git a/tests/unit/test_moto.py b/tests/unit/test_moto.py
@@ -1,6 +1,8 @@
 import pytest
+from moto.core.exceptions import ServiceException
 
-from localstack.services.moto import get_dispatcher
+from localstack.aws.api import CommonServiceException
+from localstack.services.moto import ServiceExceptionTranslator, get_dispatcher
 
 
 def test_get_dispatcher_for_path_with_optional_slashes():
@@ -11,3 +13,22 @@ def test_get_dispatcher_for_path_with_optional_slashes():
 def test_get_dispatcher_for_non_existing_path_raises_not_implemented():
     with pytest.raises(NotImplementedError):
         get_dispatcher("route53", "/non-existing")
+
+
+def test_service_exception_translator_context_manager():
+    class WeirdException(ServiceException):
+        code = "WeirdErrorCode"
+
+    # Ensure Moto ServiceExceptions are translated to ASF CommonServiceException
+    with pytest.raises(CommonServiceException) as exc:
+        with ServiceExceptionTranslator():
+            raise WeirdException()
+    assert exc.value.code == "WeirdErrorCode"
+
+    # Ensure other exceptions are not affected
+    with pytest.raises(RuntimeError):
+        raise RuntimeError()
+
+    with pytest.raises(RuntimeError):
+        with ServiceExceptionTranslator():
+            raise RuntimeError()
