JSONPatch Formatter Results Are Invalid With Multiple Moves

[mgreystone]

When performing multiple move operations, the results from the jsonpatch formatter are not correct. Applying them does not results in the desired object.

Here is an example reversing the items in an array.

import { create } from 'jsondiffpatch'
import { format } from 'jsondiffpatch/formatters/jsonpatch'
import jsonpatch from 'jsonpatch'

const jsondiffpatch = create({
  arrays: {
    detectMove: true,
  },
});

const a = ["first", "second", "third", "fourth", "fifth"];
const b = ["fifth", "fourth", "third", "second", "first"];

const diff = jsondiffpatch.diff(a, b);
/*
diff is {
  _t: 'a',
  _1: [ '', 3, 3 ],
  _2: [ '', 2, 3 ],
  _3: [ '', 1, 3 ],
  _4: [ '', 0, 3 ]
}
*/

const patchedwithdiff = jsondiffpatch.patch(a, diff)
/*
This is correct:
patchedwithdiff is [ 'fifth', 'fourth', 'third', 'second', 'first' ]
*/

const patch = format(diff, a)
/*
This is not correct:
patch is: [
  { op: 'move', from: '/1', path: '/3' },
  { op: 'move', from: '/2', path: '/2' },
  { op: 'move', from: '/3', path: '/1' },
  { op: 'move', from: '/4', path: '/0' }
]
---
There are many ways to get the desired results,
but one way looks like this: [
  { op: 'move', from: '/0', path: '/4' },
  { op: 'move', from: '/0', path: '/4' },
  { op: 'move', from: '/0', path: '/4' },
  { op: 'move', from: '/0', path: '/4' },
  { op: 'move', from: '/0', path: '/4' },
]
*/

const patchedwithjson = jsonpatch.apply_patch(a, patch)
/*
patchedwithjson is: [ 'first', 'fifth', 'fourth', 'third', 'second' ]
we expected: ["fifth", "fourth", "third", "second", "first"]
*/