Unable to trigger a task module from onSubmitAction

[meduck]

I was trying to trigger a task module from inside the onSubmitAction function (implemented from IMessagingExtensionMiddlewareProcessor) but it will always fail with an error. I trigger this from the command bar (this is the important bit)

I found that MessagingExtensionMiddleware.onTurn will always return the response of the onSubmitAction as the value of a composeExtension property which can be seen here:

index - line 267

switch(...)
...
   default:
     result = yield this.processor.onSubmitAction(context, context.activity.value);
      body = {
          composeExtension: result,
      };
  break;
}
context.sendActivity({
  type: INVOKERESPONSE,
  value: {
      body,
      status: 200,
  },
});

If I change the composeExtension to task then it works fine.

Am I doing something wrong or is there no way to call another task module? Here is a cutdown of my code (this code would work if I done the above change of updating composeExtension to task)

export default class HelpDeskMessageExtension implements IMessagingExtensionMiddlewareProcessor {

    public async onFetchTask(): Promise<MessagingExtensionResult | TaskModuleContinueResponse | TaskModuleMessageResponse> {
        return Promise.resolve<TaskModuleContinueResponse>({
            type: "continue",
            value: {
                url: `${process.env.HostName}/action.html`,
            },
        });
    }


    public async onSubmitAction(context: TurnContext): Promise<MessagingExtensionResult> {
        return Promise.resolve<MessagingExtensionResult>({
            type: "continue",
            value: {
                card: CardFactory.adaptiveCard({
                    type: 'AdaptiveCard',
                    body: [{type: 'TextBlock', text: "text"}],
                    actions: [{type: 'Action.Submit', title: 'Ok', data: {endFlow: true }}],
                })
            }
        });
    }

}