feat: support array within array

[hacksparrow]

Description

POST request body:

 { items": [
    [
      {"name": "APPLE"},
      {"serial": 67}
    ]
  ]
}

Currently stored as:

 { "items": [
    {
      "0": {
        "name": "APPLE"
      },
      "1": {
        "serial": 67
      }
    }
  ]
}

Will be stored as:

 { items": [
    [
      {
        "name": "APPLE"
      },
      {
        "serial": 67
      }
    ]
  ]}

Related issues

strongloop/loopback#4132

Checklist

• New tests added or existing tests modified to cover all changes
• Code conforms with the style
  guide

[hacksparrow]

@raymondfeng @bajtos please review.

[bajtos]

LGTM.

I think this will not handle the case where the nested items need to be converted from plain data objects into model instances, but that can be fixed later. The change proposed here is a good incremental improvement.

Please get at least one or two more approvals before landing. I am not very familiar with juggler code base, I may have missed a problem that's not obvious.

[hacksparrow]

Agreed. I am aware that there can be other conditions when the resulting object will be unexpected. Let's just focus on the reported bug at the moment.

[raymondfeng]

Do we want to test if item instanceof List to convert List, which is a special array?

[hacksparrow]

In that case it is breaking some test cases. The data structure which elicited the bug is a very unlikely one. This PR takes care of that scenario without side effects.

I think we should land the PR and move on.

[raymondfeng]

ok