Unable to use Google Translate API

[chrsmith]

I'm pretty sure the problem is entirely on my end. But I can't quite figure out what I'm doing wrong. In short, I'm unable to successfully use the Google Translate API. Despite constructing what appears to be a valid request message, I keep getting the same error, "Missing required field target":

Unhandled Exception: Google.GoogleApiException: Google.Apis.Requests.RequestError
Missing required field target [400]
Errors [
	Message[Missing required field target] Location[ - ] Reason[badRequest] Domain[global]
]

Here's my F# code. I'm using Application Default Credentials from gcloud, and calling the Google Speech API works. (Although that is using gRPC/veneer, so it's a very different codepath.)

// Google Translate .NET Client Library bug repro.
//
// NuGet Dependencies:
// Google.Apis.Translate.v2 (1.29.1.875)
// Newtonsoft.Json (10.0.3) -- Just for printing JSON objects.

open System.Collections.Generic

open Google.Apis.Auth.OAuth2
open Google.Apis.Services
open Google.Apis.Translate.v2

// Just for showing the serialized form of the API request body.
open Newtonsoft.Json

[<EntryPoint>]
let main argv =
    printfn "Use Google Translate API"

    let googleCreds = GoogleCredential.GetApplicationDefault()
    let baseClient = new BaseClientService.Initializer(HttpClientInitializer = googleCreds)
    let translateSvc = new TranslateService(baseClient)

    let text = new List<string>()
    text.Add("Help! I do not know Spanish and am lost in Mexico.")

    let translateReq = new Data.TranslateTextRequest()
    translateReq.Format <- "text"
    translateReq.Q <- text
    translateReq.Source <- "en"
    translateReq.Target <- "es"

    // Confirm the request object is constructed correctly.
    printfn "%A: %A [%s->%s]" translateReq translateReq.Q translateReq.Source translateReq.Target 
    printfn "Request in JSON:\n%s" <| JsonConvert.SerializeObject(translateReq)
 
    let reqObj = translateSvc.Translations.Translate(translateReq)
    let respObj = reqObj.Execute()

    printfn "Success! Response:\n%A" respObj

    0

And typical output. Notice how the "target" field is found in the JSON serialization of the object.

$ dotnet run
Use Google Translate API
Google.Apis.Translate.v2.Data.TranslateTextRequest: seq ["Help! I do not know Spanish and am lost in Mexico."] [en->es]
Request in JSON:
{"format":"text","model":null,"q":["Help! I do not know Spanish and am lost in Mexico."],"source":"en","target":"es","ETag":null}

Unhandled Exception: Google.GoogleApiException: Google.Apis.Requests.RequestError
Missing required field target [400]
Errors [
	Message[Missing required field target] Location[ - ] Reason[badRequest] Domain[global]
]

   at Google.Apis.Requests.ClientServiceRequest`1.Execute()

Any ideas on what the issue could be?

[jskeet]

Will try to reproduce this tomorrow. A couple of questions though:

• Any reason you're not using Google.Cloud.Translation.V2?
• Have you tried logging the actual HTTP request as per https://googlecloudplatform.github.io/google-cloud-dotnet/docs/faq.html#how-can-i-trace-requests-and-responses-in-rest-based-apis?

[chrsmith]

I was unaware there was an updated Translation client. (I didn't read the fine print of the older one's NuGet description, and the Google.Cloud.Translation.V2 appeared much lower in the list.)

After switching to use that, everything works like expected. Thanks! Given that I have a much better workaround, feel free to lower the priority of this bug. Though given the severity of not being able to use the API client library at all, perhaps it still deserves some attention. (Though I still assume it's a problem on my end.)

For posterity:

// open Google.Cloud.Translation.V2
    let translateClient = TranslationClient.Create()
    let translation = translateClient.TranslateText("Help! I do not know Spanish and am lost in Mexico.",
                                                    getLanguageCode Spanish,
                                                    getLanguageCode English)
    printfn "translation: %s" translation.TranslatedText
// ¡Ayuda! No sé español y estoy perdido en México.

I hooked up trace logging. Here is the dump. I updated the flags to also include the request body, which being zipped, wasn't especially useful.

$ dotnet run
Use Google Translate API
D2017-09-17 17:00:56.768190 Google.Apis.Auth.OAuth2.DefaultCredentialProvider Loading Credential from file /Users/chris/.config/gcloud/application_default_credentials.json
W2017-09-17 17:00:56.967163 Google.Apis.Auth.OAuth2.Flows.AuthorizationCodeFlow Datastore is null, as a result the user's credential will not be stored
D2017-09-17 17:00:56.973497 Google.Apis.Http.HttpClientFactory Handler was created. SupportsRedirectConfiguration=True, SupportsAutomaticDecompression=True
D2017-09-17 17:00:56.985796 Google.Apis.Http.HttpClientFactory Handler was created. SupportsRedirectConfiguration=True, SupportsAutomaticDecompression=True
Google.Apis.Translate.v2.Data.TranslateTextRequest: seq ["Help! I do not know Spanish and am lost in Mexico."] [en->es]
Request in JSON:
{"format":"text","model":null,"q":["Help! I do not know Spanish and am lost in Mexico."],"source":"en","target":"es","ETag":null}
D2017-09-17 17:00:57.213647 Google.Apis.Auth.OAuth2.UserCredential Token has expired, trying to refresh it.
D2017-09-17 17:00:57.226819 Google.Apis.Http.ConfigurableMessageHandler Request[00000001] (triesRemaining=3) URI: 'https://www.googleapis.com/oauth2/v4/token'
D2017-09-17 17:00:57.340042 Google.Apis.Http.ConfigurableMessageHandler Response[00000001] Response status: OK 'OK'
I2017-09-17 17:00:57.361032 Google.Apis.Auth.OAuth2.UserCredential Access token was refreshed successfully
D2017-09-17 17:00:57.368702 Google.Apis.Http.ConfigurableMessageHandler Request[00000001] Headers:
  [User-Agent] 'bug-repro; google-api-dotnet-client/1.29.1.0; (gzip)'
  [Authorization] 'Bearer [redacted]'
  [Content-Encoding] 'gzip'
  [Content-Type] 'application/json; charset=utf-8'
D2017-09-17 17:00:57.370660 Google.Apis.Http.ConfigurableMessageHandler Request[00000001] Body: '...............0...U>.\1@&..'......h....R..)o..2K.....Q...K.........gd.y.m>.:....X........K...{.....^..QH}.?..m...b..q...'
D2017-09-17 17:00:57.457021 Google.Apis.Http.ConfigurableMessageHandler Response[00000001] Body: '{.  "error": {.    "code": 400,.    "message": "Missing required field target",.    "errors": [.      {.        "message": "Missing required field target",.        "domain": "global",.        "reason": "badRequest".      }.    ],.    "status": "INVALID_ARGUMENT".  }.}.'

Unhandled Exception: Google.GoogleApiException: Google.Apis.Requests.RequestError
Missing required field target [400]
Errors [
	Message[Missing required field target] Location[ - ] Reason[badRequest] Domain[global]
]

   at Google.Apis.Requests.ClientServiceRequest`1.Execute()

Updated code in case you can't reproduce this in C#:

// Google Translate .NET Client Library bug repro.
//
// NuGet Dependencies:
// Google.Apis.Translate.v2 (1.29.1.875)
// Newtonsoft.Json (10.0.3) -- Just for printing JSON objects.
open Google
open System.Collections.Generic

open Google.Apis.Auth.OAuth2
open Google.Apis.Services
open Google.Apis.Translate.v2

open Google.Apis.Logging
open Google.Apis.Http

// Just for showing the serialized form of the API request body.
open Newtonsoft.Json

[<EntryPoint>]
let main argv =
    printfn "Use Google Translate API"

    // Enable request logging.
    ApplicationContext.RegisterLogger(new ConsoleLogger(LogLevel.All));

    let googleCreds = GoogleCredential.GetApplicationDefault()
    let baseClient = new BaseClientService.Initializer(HttpClientInitializer = googleCreds, 
ApplicationName = "bug-repro")
    let translateSvc = new TranslateService(baseClient)

    translateSvc.HttpClient.MessageHandler.LogEvents <-
        ConfigurableMessageHandler.LogEventType.RequestHeaders ||| ConfigurableMessageHandler.LogEventType.RequestBody
        ||| ConfigurableMessageHandler.LogEventType.ResponseBody;

    let text = new List<string>()
    text.Add("Help! I do not know Spanish and am lost in Mexico.")

    let translateReq = new Data.TranslateTextRequest()
    translateReq.Format <- "text"
    translateReq.Q <- text
    translateReq.Source <- "en"
    translateReq.Target <- "es"

    // Confirm the request object is constructed correctly.
    printfn "%A: %A [%s->%s]" translateReq translateReq.Q translateReq.Source translateReq.Target 
    printfn "Request in JSON:\n%s" <| JsonConvert.SerializeObject(translateReq)
 

    // Configure which events the message handler will log.


    let reqObj = translateSvc.Translations.Translate(translateReq)
    let respObj = reqObj.Execute()

    printfn "Success! Response:\n%A" respObj

    0

[jskeet]

Thanks - I had to change to use scoped credentials:

let googleCreds = GoogleCredential.GetApplicationDefault().CreateScoped("https://www.googleapis.com/auth/cloud-platform")

but then I managed to reproduce the problem.

Additionally setting GZipEnabled = false in the BaseClientInitializer constructor let me see the body of the request:

D2017-09-18 07:50:06.016869 Google.Apis.Http.ConfigurableMessageHandler Request[00000001] Body:
 '{"data":{"format":"text","q":["Help! I do not know Spanish and am lost in Mexico."],"source":"en","target":"es"}}'

Sure enough, the target is present. Will now try in C#...

[jskeet]

Reproduced in C# as well:

using System;
using System.Collections.Generic;
using System.Linq;
using Google.Apis.Auth.OAuth2;
using Google.Apis.Services;
using Google.Apis.Translate.v2;
using Google.Apis.Translate.v2.Data;

class Program
{
    static void Main()
    {
        var creds = GoogleCredential
            .GetApplicationDefault()
            .CreateScoped("https://www.googleapis.com/auth/cloud-platform");
        
        var service = new TranslateService(new BaseClientService.Initializer
        {
            ApplicationName = "Issue1086",
            HttpClientInitializer = creds
        });
        
        var request = new TranslateTextRequest
        {
            Q = new List<string> { "Help! I do not know Spanish and am lost in Mexico." },
            Format = "Text",
            Source = "en",
            Target = "es"
        };
        
        var response = service.Translations.Translate(request).Execute();
        Console.WriteLine(string.Join(",", response.Translations.Select(t => t.TranslatedText)));
    }
}

The Google.Cloud.Translation.V2 library uses a different call to make the request, which is why it's not seeing this issue. The working C# would be:

using Google.Apis.Auth.OAuth2;
using Google.Apis.Services;
using Google.Apis.Translate.v2;
using Google.Apis.Util;
using System;
using System.Linq;
using static Google.Apis.Translate.v2.TranslationsResource;

class Program
{
    static void Main()
    {
        var creds = GoogleCredential
            .GetApplicationDefault()
            .CreateScoped("https://www.googleapis.com/auth/cloud-platform");
        
        var service = new TranslateService(new BaseClientService.Initializer
        {
            ApplicationName = "Issue1086",
            HttpClientInitializer = creds
        });

        var strings = new Repeatable<string>(new[] { "Help! I do not know Spanish and am lost in Mexico." });
        var request = service.Translations.List(strings, "es");
        request.Format = ListRequest.FormatEnum.Text;
        request.Source = "en";        
        
        var response = request.Execute();
        Console.WriteLine(string.Join(",", response.Translations.Select(t => t.TranslatedText)));
    }
}

I'll file an internal issue to see what's going on with the previous request.

[chrsmith]

Thanks @jskeet, I appreciate the time you spent helping out! Hopefully(?) it's a legitimate bug and worth the time.

[chrisdunelm]

@jskeet discovered that this is almost certainly a bug in the handling of the "dataWrapper" feature.
We'll fix the bug and test that the whole translate API works.