[FeatureRequest] type serviceBus direction out - specify content-type

[freedev]

It seems not possible define the content-type for an out message.
In my function.json I have an out serviceBus that works fine but I'm unable to define the content-type.

{
  "type": "serviceBus",
  "direction": "out",
  "connection": "AzureServiceBusConnectionString",
  "name": "outmsg",
  "topicName": "%DIGICD_NOTIFICATION%"
}

but outmsg is defined as azure.functions.Out[str].
Honestly, I'm not fluent in Python, It seems to me that Out is a monad, an object that contains a string.
it is not clear if we can define Out with another type other than str.
And in any case even if the message is sent as str with content-type for the receiver is application/xml; charset=utf-8

I think we should be able at least to specify the content type. Something like this:

outmsg.set(json.dumps({ 'key':'value' })) 
outmsg.setContentType('application/json') 

Or we could extend the function.json adding the default content type parameter of out messages.

[freedev]

any update here?

[hallvictoria]

Hi @freedev, sorry for the delay on this. The Out class is intended to represent an output binding. The class definition looks like this:

T = typing.TypeVar('T')
class Out(abc.ABC, typing.Generic[T]):

T is a generic type, which means that you can define what type the output will be (like str). Essentially, when you write Out[str], you're saying "this output will be of type str".

Each binding extension has specific types that it expects, so I feel having a method like setContentType would be misleading. For example, in case of a CosmosDB output binding, func.Out[int] is invalid. There are no current plans to support this scenario, so something like outmsg.setContentType('int') would be unhelpful.

For Blobs, we do list out the supported types for Out. I'll look at updating our documentation to do this for all the bindings.

[hallvictoria]

Documentation has been updated, please let me know if there are any further questions.

[freedev]

Hi @hallvictoria, sorry, I think you missed the question. The problem I'm raising is about the content type of the message sent in the service bus. We should be able to set the content type of the object outmsg, even if it contains a string, we should be able to set the string is a 'application/json' or an xml, etc.