Add more expressive exception when function not found

client/qiskit_serverless/utils/json.py

@@ -139,17 +139,28 @@ def safe_json_request(
     if error_message:
         raise QiskitServerlessException(error_message)
 
-    if response is not None and not response.ok:
-        raise QiskitServerlessException(
-            format_err_msg(
-                response.status_code,
-                str(response.text),
-            )
-        )
-
     decoding_error_message: Optional[str] = None
     try:
         json_data = json.loads(response.text)
+        if response is not None and not response.ok:
+            # When response is not ok, the expected json
+            # response is a dictionary with a field
+            # that contains the error message. The key
+            # varies between messages, so appending all
+            # values to a string allows to capture all
+            # potential messages
+            print("RESPONSE JSON", json_data)
+            error_msg = ""
+            for error_string in json_data.values():
+                error_msg += str(error_string)
+            print("ERROR MSG", error_msg)
+
+            raise QiskitServerlessException(
+                format_err_msg(
+                    response.status_code,
+                    str(error_msg),
+                )
+            )
     except json.JSONDecodeError as json_error:
         decoding_error_message = format_err_msg(
             ErrorCodes.JSON1001,

gateway/api/views/programs.py

@@ -3,6 +3,7 @@
 
 Version views inherit from the different views.
 """
+
 import logging
 import os
 
@@ -290,15 +291,32 @@ def get_by_title(self, request, title):
                 title=function_title,
                 provider_name=provider_name,
             )
+            if function is None:
+                return Response(
+                    {
+                        "message": (
+                            f"Program '{function_title}' for provider '{provider_name}' "
+                            "was not found or you do not have permission to view it."
+                        )
+                    },
+                    status=status.HTTP_404_NOT_FOUND,
+                )
         else:
             function = self.function_repository.get_user_function(
                 author=author, title=function_title
             )
+            if function is None:
+                return Response(
+                    {
+                        "message": (
+                            f"User program '{function_title}' was not found or "
+                            "you do not have permission to view it."
+                        )
+                    },
+                    status=status.HTTP_404_NOT_FOUND,
+                )
 
-        if function:
-            return Response(self.get_serializer(function).data)
-
-        return Response(status=404)
+        return Response(self.get_serializer(function).data)
 
     # This end-point is deprecated and we need to confirm if we can remove it
     @_trace

releasenotes/notes/improve-exception-404-9815392d005df623.yaml

@@ -0,0 +1,17 @@
+---
+fixes:
+  - |
+    Fixed a bug in the json decoder that would crop the response details to the first character when 
+    gateway errors were raised. This utility now forwards the full error message to the raised 
+    ``QiskitServerlessException``.
+
+  - |
+    Fixed error handling when a function is not found. Instead of providing a 
+    bare 404 error, the ``QiskitServerlessException`` now contains a more meaningful error message::
+
+      QiskitServerlessException: 
+      | Message: Http bad request.
+      | Code: 404
+      | Details: User program 'my-program' was not found or you do not have permission to view it.
+
+    Fixes https://github.com/Qiskit/qiskit-serverless/issues/1773.

tests/docker/test_docker.py

@@ -390,3 +390,24 @@ def test_get_filtered_jobs(self, serverless_client: ServerlessClient):
 
         succeeded_jobs = serverless_client.jobs(status="SUCCEEDED")
         assert len(succeeded_jobs) >= 3
+
+    def test_wrong_function_name(self, serverless_client: ServerlessClient):
+        """Integration test for retrieving a function that isn't accessible."""
+
+        arguments_function = QiskitFunction(
+            title="pattern-with-arguments",
+            entrypoint="pattern_with_arguments.py",
+            working_dir=resources_path,
+        )
+
+        expected_message = (
+            "User program 'wrong-title' was not found or you do not "
+            "have permission to view it."
+        )
+
+        serverless_client.upload(arguments_function)
+
+        with raises(QiskitServerlessException) as exc_info:
+            serverless_client.function("wrong-title")
+
+        assert str(exc_info.value) == expected_message