Bad error message when misspelling docs in _mget

[suederade]

Elasticsearch version: 5.x

JVM version: 8

OS version: OSX 10.11.6

Description of the problem including expected versus actual behavior: When searching _mget and passing {"doc": []} (misspelling docs), should throw a better error message when seeing the array.

Steps to reproduce:
doc instead of docs:

GET _mget
{
  "doc" : [
    {
      "_index" : "orders-current",
      "_type" : "order",
      "_id" : 6
    },
    {
      "_index" : "products",
      "_type" : "product",
      "_id" : 4321
    }
  ]
}

Error:

{
  "error": {
    "root_cause": [
      {
        "type": "action_request_validation_exception",
        "reason": "Validation Failed: 1: no documents to get;"
      }
    ],
    "type": "action_request_validation_exception",
    "reason": "Validation Failed: 1: no documents to get;"
  },
  "status": 400
}

@dakrone

[olcbean]

Do you mean that instead no documents to get; the msg should changed to Unknown key for a START_OBJECT in [doc]. (similar to the one displayed for search)?

[rjernst]

Looks like the keys should be validated here. And the value type should also be validated as well. Right now it only looks for array. Anything else is silently ignored.