[Dialogflow] WebhookRequest parse exception in .NET Core app

Environment details

• OS: Windows 10
• .NET version: .NET Core 3.1
• Package name and version:
  • Google.Cloud.Dialogflow.V2 1.2.0;
  • Google.Protobuf 3.11.4.

Steps to reproduce

1. Run the sample from https://googleapis.github.io/google-cloud-dotnet/docs/Google.Cloud.Dialogflow.V2/index.html for .NET Core;
2. When calling the following line in the sample:

request = jsonParser.Parse<WebhookRequest>(reader);

I get the following exception:

Synchronous operations are disallowed. Call ReadAsync or set AllowSynchronousIO to true instead.

To try to fix this issue I included the following lines in my ConfigureServices method in the Startup class:

services.Configure<KestrelServerOptions>(options =>
{
	options.AllowSynchronousIO = true;
});
																		
services.Configure<IISServerOptions>(options =>
{
	options.AllowSynchronousIO = true;
});

However after doing this I start getting this exception:

Unexpected end of document in state: StartOfDocument

   at Google.Protobuf.JsonTokenizer.JsonTextTokenizer.ValidateState(State validStates, String errorPrefix)
   at Google.Protobuf.JsonTokenizer.JsonTextTokenizer.NextImpl()
   at Google.Protobuf.JsonTokenizer.Next()
   at Google.Protobuf.JsonParser.Merge(IMessage message, JsonTokenizer tokenizer)
   at Google.Protobuf.JsonParser.Merge(IMessage message, TextReader jsonReader)
   at Google.Protobuf.JsonParser.Parse[T](TextReader jsonReader)

The workaround I found for this was replacing:

request = jsonParser.Parse<WebhookRequest>(reader);

To:

string requestAsString;
// (...)
requestAsString = await reader.ReadToEndAsync();
request = jsonParser.Parse<WebhookRequest>(requestAsString);

Here is the request I’m getting from DialogFlow:

{
  "responseId": "55727bcc-7d89-4fd5-8c1f-20f9e4d8d19c-7f245a81",
  "queryResult": {
    "queryText": "Meu nome é Fagner",
    "parameters": {
      "name": "Fagner"
    },
    "allRequiredParamsPresent": true,
    "fulfillmentMessages": [{
      "text": {
        "text": [""]
      }
    }],
    "outputContexts": [{
      "name": "projects/<project id>/agent/sessions/<session id>/contexts/actions_capability_account_linking",
      "parameters": {
        "name": "Fagner",
        "name.original": "Fagner"
      }
    }, {
      "name": "projects/<project id>/agent/sessions/<session id>/contexts/actions_capability_audio_output",
      "parameters": {
        "name": "Fagner",
        "name.original": "Fagner"
      }
    }, {
      "name": "projects/<project id>/agent/sessions/<session id>/contexts/actions_capability_media_response_audio",
      "parameters": {
        "name": "Fagner",
        "name.original": "Fagner"
      }
    }, {
      "name": "projects/<project id>/agent/sessions/<session id>/contexts/actions_capability_screen_output",
      "parameters": {
        "name": "Fagner",
        "name.original": "Fagner"
      }
    }, {
      "name": "projects/<project id>/agent/sessions/<session id>/contexts/google_assistant_input_type_voice",
      "parameters": {
        "name": "Fagner",
        "name.original": "Fagner"
      }
    }, {
      "name": "projects/<project id>/agent/sessions/<session id>/contexts/__system_counters__",
      "lifespanCount": 1,
      "parameters": {
        "no-input": 0.0,
        "no-match": 0.0,
        "name": "Fagner",
        "name.original": "Fagner"
      }
    }],
    "intent": {
      "name": "projects/<project id>/agent/intents/<session id>",
      "displayName": "greetings-intent"
    },
    "intentDetectionConfidence": 1.0,
    "languageCode": "en"
  },
  "originalDetectIntentRequest": {
    "source": "google",
    "version": "2",
    "payload": {
      "user": {
        "locale": "en-US",
        "lastSeen": "2020-02-22T23:44:35Z",
        "userVerificationStatus": "VERIFIED"
      },
      "conversation": {
        "conversationId": "<conversation id>",
        "type": "ACTIVE",
        "conversationToken": "[\"__system_counters__\"]"
      },
      "inputs": [{
        "intent": "actions.intent.TEXT",
        "rawInputs": [{
          "inputType": "VOICE",
          "query": "Meu nome é Fagner"
        }],
        "arguments": [{
          "name": "text",
          "rawText": "Meu nome é Fagner",
          "textValue": "Meu nome é Fagner"
        }]
      }],
      "surface": {
        "capabilities": [{
          "name": "actions.capability.ACCOUNT_LINKING"
        }, {
          "name": "actions.capability.AUDIO_OUTPUT"
        }, {
          "name": "actions.capability.MEDIA_RESPONSE_AUDIO"
        }, {
          "name": "actions.capability.SCREEN_OUTPUT"
        }]
      },
      "isInSandbox": true,
      "availableSurfaces": [{
        "capabilities": [{
          "name": "actions.capability.WEB_BROWSER"
        }, {
          "name": "actions.capability.AUDIO_OUTPUT"
        }, {
          "name": "actions.capability.SCREEN_OUTPUT"
        }]
      }],
      "requestType": "SIMULATOR"
    }
  },
  "session": "projects/<project id>/agent/sessions/<session id>"
}

Can we update the docs with my fix?

Also, I will report this issue in the protobuf repo to keep you in the loop for when this is fixed.

[jskeet]

Righto - I’ve got a PR out to update the docs to show the ReadToEndAsync version, so let’s just not worry about the other exception 😃

[jskeet]

(I don’t understand why allowing synchronous IO doesn’t just make it work, but it’s simpler to document the workaround.)