How to catch mutation errors from the server

I’ve got a question about error handling client side.

My server returns this on validation error:

{
  "data": {
    "auth": null
  },
  "errors": [
    {
      "message": "An authentication error has occurred",
      "name": "AuthenticationError",
      "time_thrown": "2017-03-26T01:26:50.439Z",
      "data": {
        "errors": {
          "login": "Authentication failed.  Invalid email or password"
        }
      }
    }
  ]
}

I’d like to get access to the validation errors using apollo-client mutation - something like this:

    return auth(values)  //<— this is a mutation
      .then(({data}) => {
        loginThenRedirect(data); // <--- log user in
      })
      .catch((mutationErrors) => {
        const {errors} = mutationErrors.data  // <--- doesn't work
        this.setState({errors})  // <— display the errors
      });

But mutationErrors get swallowed up and only show a string Error: GraphQL error: An authentication error has occurred…

Is there a way to get the contents of the server error so I can display it client side?

[variousauthors]

When I catch the error from a mutation like this,

.catch((e) => { console.log(e) })

The following message is logged to the console,

Error: GraphQL error: Unauthorized
    at new ApolloError (ApolloError.js:32)
    at QueryManager.js:119
    at <anonymous>

So I got the impression that this issue was still occurring.

When I inspected the object more closely, like this,

.catch((e) => { console.log(e.graphQLErrors) })

It logged an array of error objects.

So the problem was my expectations, not the object itself. Just putting this here for posterity, in case anyone else is caught off-guard by this behaviour.

[kojuka]

@helfer Ok that worked out.

I was able to get the error object by doing const error = JSON.parse(JSON.stringify(mutationError))

not sure if there is a better way to turn the string into an object but this works for me.

Thank you all for the help!