Event Grid output binding does not work on Python

In the process of updating the documentation for the Event Grid output binding (see this PR), I discovered that the output binding does not work correctly with Python functions. It does work correctly for .NET and Node.js. (Note I have opened a separate issue to log that this doesn’t work for Java either.)

• I used this function.json and this function code.
• When I ran the function, I got this error:

Result: Failure
Exception: FunctionLoadError: cannot load the MyFunction function: Python return annotation "EventGridEvent" does not match binding type "eventGrid"
Stack:   File "/azure-functions-host/workers/python/3.7/LINUX/X64/azure_functions_worker/dispatcher.py", line 245, in _handle__function_load_request
    function_id, func, func_request.metadata)
  File "/azure-functions-host/workers/python/3.7/LINUX/X64/azure_functions_worker/functions.py", line 241, in add_function
    f'Python return annotation "{return_pytype.__name__}" '

• I wonder if the issue is that the binding extension bundle does not include a reference to the eventGrid output binding (only to eventGridTrigger) - I have no idea how this works though, and if it’s sufficient to simply put a PR adding that one line to the extensions.json or if something more needs to be done to wire it up.

[vrdmr]

Thanks @johndowns. I’ve opened a documentation PR: https://github.com/MicrosoftDocs/azure-docs/pull/54037

I’ll close this issue as it is resolved from our side and is now supported in the newly released azure-functions-python-1.2.1 module.

[johndowns]

@vrdmr - yes, I believe that’s the page. It’s been moved since I worked on it but it looks like that’s the one to update.