Unintuitive error message when UseDevelopmentStorage=true and Storage Emulator isn't running

[arerlend]

@cgillum follow-up on comment on #72

The error message below is a bit unintuitive, especially "The function 'E1_HelloSequence' doesn't exist... The following are the active orchestrator functions: ." in particular. Just a nonessential QoL fix for DF newcomers that might prevent some frayed nerves.

{
    "id": "...",
    "requestId": "...",
    "statusCode": 500,
    "errorCode": 0,
    "message": "Exception while executing function: HttpStart -> The function 'E1_HelloSequence' doesn't exist, is disabled, or is not an orchestrator function. The following are the active orchestrator functions: .",
    "errorDetails": "Microsoft.Azure.WebJobs.Host.FunctionInvocationException : Exception while executing function: HttpStart ---> System.ArgumentException : The function 'E1_HelloSequence' doesn't exist, is disabled, or is not an orchestrator function. The following are the active orchestrator functions: .\r\n   at Microsoft.Azure.WebJobs.Extensions.DurableTask.DurableTaskExtension.AssertOrchestratorExists(String name,String version)\r\n   at async Microsoft.Azure.WebJobs.DurableOrchestrationClient.StartNewAsync(??)\r\n   at CallSite.Target(Closure ,CallSite ,Object )\r\n   at System.Dynamic.UpdateDelegates.UpdateAndExecute1[T0,TRet](CallSite site,T0 arg0)\r\n   at async VSSample.HttpStart.Run(HttpRequestMessage req,DurableOrchestrationClient starter,String functionName,TraceWriter log)\r\n   at async Microsoft.Azure.WebJobs.Host.Executors.FunctionInvoker`2.InvokeAsync[TReflected,TReturnValue](Object instance,Object[] arguments)\r\n   at async Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor.InvokeAsync(IFunctionInvoker invoker,ParameterHelper parameterHelper,CancellationTokenSource timeoutTokenSource,CancellationTokenSource functionCancellationTokenSource,Boolean throwOnTimeout,TimeSpan timerInterval,IFunctionInstance instance)\r\n   at async Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor.ExecuteWithWatchersAsync(IFunctionInstance instance,ParameterHelper parameterHelper,TraceWriter traceWriter,CancellationTokenSource functionCancellationTokenSource)\r\n   at async Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor.ExecuteWithLoggingAsync(??)\r\n   at async Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor.ExecuteWithLoggingAsync(??) \r\n   End of inner exception\r\n   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n   at async Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor.ExecuteWithLoggingAsync(??)\r\n   at async Microsoft.Azure.WebJobs.Host.Executors.FunctionExecutor.TryExecuteAsync(IFunctionInstance functionInstance,CancellationToken cancellationToken)\r\n   at Microsoft.Azure.WebJobs.Host.Executors.ExceptionDispatchInfoDelayedException.Throw()\r\n   at async Microsoft.Azure.WebJobs.JobHost.CallAsync(??)\r\n   at async Microsoft.Azure.WebJobs.Script.ScriptHost.CallAsync(String method,Dictionary`2 arguments,CancellationToken cancellationToken)\r\n   at async Microsoft.Azure.WebJobs.Script.WebHost.WebScriptHostManager.HandleRequestAsync(FunctionDescriptor function,HttpRequestMessage request,CancellationToken cancellationToken)\r\n   at async Microsoft.Azure.WebJobs.Script.Host.FunctionRequestInvoker.ProcessRequestAsync(HttpRequestMessage request,CancellationToken cancellationToken,WebScriptHostManager scriptHostManager,WebHookReceiverManager webHookReceiverManager)\r\n   at async Microsoft.Azure.WebJobs.Script.WebHost.Controllers.FunctionsController.<>c__DisplayClass3_0.<ExecuteAsync>b__0(??)\r\n   at async Microsoft.Azure.WebJobs.Extensions.Http.HttpRequestManager.ProcessRequestAsync(HttpRequestMessage request,Func`3 processRequestHandler,CancellationToken cancellationToken)\r\n   at async Microsoft.Azure.WebJobs.Script.WebHost.Controllers.FunctionsController.ExecuteAsync(HttpControllerContext controllerContext,CancellationToken cancellationToken)\r\n   at async System.Web.Http.Dispatcher.HttpControllerDispatcher.SendAsync(HttpRequestMessage request,CancellationToken cancellationToken)\r\n   at async System.Web.Http.Dispatcher.HttpControllerDispatcher.SendAsync(HttpRequestMessage request,CancellationToken cancellationToken)\r\n   at async Microsoft.Azure.WebJobs.Script.WebHost.Handlers.WebScriptHostHandler.SendAsync(HttpRequestMessage request,CancellationToken cancellationToken)\r\n   at async Microsoft.Azure.WebJobs.Script.WebHost.Handlers.SystemTraceHandler.SendAsync(HttpRequestMessage request,CancellationToken cancellationToken)\r\n   at async System.Web.Http.HttpServer.SendAsync(HttpRequestMessage request,CancellationToken cancellationToken)"
}

[cgillum]

Sorry for the confusion - I understand this can be confusing and frustrating when you're first trying to use the extension. When the fix for #205 is released later this week, it will also improve the error message experience here. Basically, instead of getting a "the function XXX doesn't exist", you should get a proper storage exception. I'll leave this bug open to remind myself to validate this.

[cgillum]

It looks like the latest version of the Functions CLI + Visual Studio integration automatically starts up the Storage Emulator if it's not already running. I was unable to reproduce this issue, and apparently that is why. That should take care of this issue. Even if it doesn't, the next release will give you a more useful exception message.