Add `rootParentId` option to fit the case when all rows contain a valid parentId string

[rrbe]

Why

In most cases, our tree list contains a row whose parentId field is one of null / undefined / '', but if the tree list is a subset of original tree list, chances are that the transform result is not right, no matter the throwIfOrphans option is set to true or false

example:

import { arrayToTree } from 'performant-array-to-tree'

const list = [
  { id: "aaa", parentId: "notexist" },
  { id: "bbb", parentId: "aaa" },
  { id: "ccc", parentId: "bbb" },
  { id: "ddd", parentId: "bbb" },
];
const result = arrayToTree(list, {
  dataField: null,
});
console.log(JSON.stringify(result, null, 2)); // the output is []

Suggestion

If we add an option named rootParentId, items whose parentId equals rootParentId will be treat as a root item.

The above code's output should be like this

const result = arrayToTree(list, {
  dataField: null,
  rootParentId: "notexist",
});

[
  {
    "id": "aaa",
    "parentId": "notexist",
    "children": [
      {
        "id": "bbb",
        "parentId": "aaa",
        "children": [
          {
            "id": "ccc",
            "parentId": "bbb",
            "children": []
          },
          {
            "id": "ddd",
            "parentId": "bbb",
            "children": []
          }
        ]
      }
    ]
  }
]

How

Add rootParentId into option, then replace

if (parentId === null || parentId === undefined || parentId === '') {
      rootItems.push(TreeItem)
    }

with

if (parentId === null || parentId === undefined || parentId === '' || parentId === conf.rootParentId) {
      // is a root item
      rootItems.push(TreeItem)
    }

Of course we can also make rootParentId an array, the initial value is [null, undefined, ''] and will later be merged with user defined rootParentIds

[philipstanislaus]

That makes sense to me. Would you create a PR with test cases for this suggestion?

Many thanks!

[rrbe]

I have created the pr with test cases.

All tests passed but it seems there is something wrong with circle ci config. Runing yarn run test-and-send-cov-to-coveralls, ci gives Bad response: 422 {"message":"Couldn't find a repository matching this job.","error":true} response.
So the build is blocked

[philipstanislaus]

Thanks! Could you try to push again to your branch?

[philipstanislaus]

Landed in #24

Thanks for your contribution 👍