[BUG] Writing multiple messages to a single Eventhub

Investigative information

• Timestamp: 2021-12-18T18:29:00
• Function App name: (debugging locally)
• Function name(s) (as appropriate):(debugging locally)
• Core Tools version: 4.0.3971 Commit hash: d0775d487c93ebd49e9c1166d5c3c01f3c76eaaf (64-bit)

Repro steps

The function.json file is

{
  "scriptFile": "__init__.py",
  "bindings": [
    {
      "type": "eventHubTrigger",
      "name": "inputEvent",
      "direction": "in",
      "eventHubName": "device.data.raw",
      "connection": "EVENT_HUB_CONNECTION_STRING",
      "cardinality": "one",
      "consumerGroup": "$Default",
      "dataType": "string"
    },
    {
      "type": "eventHub",
      "direction": "out",
      "name": "$return",
      "connection": "EVENT_HUB_CONNECTION_STRING",
      "eventHubName": "device.data.decoded"
    }
  ]
}

Test 1 - As per first proposition of 327

def main(inputEvent: func.EventHubEvent) -> typing.List[func.EventHubEvent]:
    return (inputEvent.get_body(), inputEvent.get_body())

Test 2 - As per first proposition of 327

def main(inputEvent: func.EventHubEvent) -> typing.List[func.EventHubEvent]:
    return (inputEvent.get_body(), inputEvent.get_body())

Test 3 - As per #192

def main(inputEvent: func.EventHubEvent) -> str:
    return (inputEvent.get_body(), inputEvent.get_body())

Expected behavior

One of the methods should be able to send several messages to Eventhub

Actual behavior

Test 1

Function can not be started

[2021-12-08T17:36:04.098Z] Executed 'Functions.decode' (Failed, Id=a20e6894-0641-48be-a974-98e13ba7517e, Duration=329ms)
[2021-12-08T17:36:04.098Z] System.Private.CoreLib: Exception while executing function: Functions.decode. System.Private.CoreLib: Result: Failure
Exception: FunctionLoadError: cannot load the decode function: has invalid non-type return annotation typing.List[azure.functions._eventhub.EventHubEvent]
Stack:   File "C:\Program Files\Microsoft\Azure Functions Core Tools\workers\python\3.9/WINDOWS/X64\azure_functions_worker\dispatcher.py", line 311, in _handle__function_load_request
    self._functions.add_function(
  File "C:\Program Files\Microsoft\Azure Functions Core Tools\workers\python\3.9/WINDOWS/X64\azure_functions_worker\functions.py", line 240, in add_function
    raise FunctionLoadError(
.

Test 2

Function can not be started

[2021-12-08T17:40:06.521Z] Executed 'Functions.decode' (Failed, Id=f3a5d015-67b4-4b50-bdb4-a4d14a3625de, Duration=256ms)
[2021-12-08T17:40:06.527Z] System.Private.CoreLib: Exception while executing function: Functions.decode. System.Private.CoreLib: Result: Failure
Exception: FunctionLoadError: cannot load the decode function: has invalid non-type return annotation typing.List[str]
Stack:   File "C:\Program Files\Microsoft\Azure Functions Core Tools\workers\python\3.9/WINDOWS/X64\azure_functions_worker\dispatcher.py", line 311, in _handle__function_load_request
    self._functions.add_function(
  File "C:\Program Files\Microsoft\Azure Functions Core Tools\workers\python\3.9/WINDOWS/X64\azure_functions_worker\functions.py", line 240, in add_function
    raise FunctionLoadError(
.

Test 3

Function is started but there is an execution error:

[2021-12-08T17:56:36.411Z] Executed 'Functions.decode' (Failed, Id=cc123efe-9b7a-419c-8e4a-a29b3be2e8cb, Duration=40ms)
[2021-12-08T17:56:36.412Z] System.Private.CoreLib: Exception while executing function: Functions.decode. System.Private.CoreLib: Result: Failure
Exception: NotImplementedError: unexpected Datum type: None
Stack:   File "C:\Program Files\Microsoft\Azure Functions Core Tools\workers\python\3.9/WINDOWS/X64\azure_functions_worker\dispatcher.py", line 427, in _handle__invocation_request
    return_value = bindings.to_outgoing_proto(
  File "C:\Program Files\Microsoft\Azure Functions Core Tools\workers\python\3.9/WINDOWS/X64\azure_functions_worker\bindings\meta.py", line 117, in to_outgoing_proto
    return datumdef.datum_as_proto(datum)
  File "C:\Program Files\Microsoft\Azure Functions Core Tools\workers\python\3.9/WINDOWS/X64\azure_functions_worker\bindings\datumdef.py", line 190, in datum_as_proto
    raise NotImplementedError(
.

Known workarounds

N/A

Contents of the requirements.txt file:

azure-functions==1.8.0
requests==2.26.0

[Oliv4945]

Thanks @YunchuWang for those explanations.

[Oliv4945]

Hi @YunchuWang, yes I still have the issue. Glad that you are able to reproduce