How can I customize the validation error response in hapi.js?

Question

When using the config.validate option on a route and a request fails due to validation, hapi returns an error like:

{
    "statusCode": 400,
    "error": "Bad Request",
    "message": "child \"weight\" fails because [\"weight\" is required]",
    "validation": {
        "source": "payload",
        "keys": [
            "weight"
        ]
    }
}

Is there a way to send a different formatted validation error?

Answer 1

There are two ways to customize the output:

1. Using the failAction attribute in config.validate:

   config: {
       validate: {
           params: {
               name: Joi.string().min(3).max(10)
           },
           failAction: function (request, reply, source, error) {
   
               error.output.payload.message = 'custom';
               return reply(error).code(400);
           }
       }
   }
   

2. Using the onPreResponse extension point:

   server.ext('onPreResponse', function (request, reply) {
   
       var response = request.response;
       if (response.isBoom && response.data.name === 'ValidationError') {
           response.output.payload.message = 'custom';
       }
   
       return reply.continue();
   });
   

See the API documentation for more details.