array unpatch get wrong result

[yangwch]

my code

// config
const instance = create({
  objectHash(obj, index) {
    if (typeof obj._id !== 'undefined') {
      return obj._id;
    }
    if (typeof obj.id !== 'undefined') {
      return obj.id;
    }
    if (typeof obj.name !== 'undefined') {
      return obj.name;
    }
    return `$$index:${index}`;
  },
  cloneDiffValues: true,
  arrays: {
    // default true, detect items moved inside the array
    // (otherwise they will be registered as remove+add)
    detectMove: true,
    // default false, the value of items moved is not included in deltas
    includeValueOnMove: false,
  },
});

const comps = [
  { id: 1, style: { zIndex: 1 } },
  { id: 2, style: { zIndex: 2 } },
  { id: 3, style: { zIndex: 3 } },
  { id: 4, style: { zIndex: 4 } },
  { id: 5, style: { zIndex: 5 } },
  { id: 6, style: { zIndex: 6 } },
  { id: 7, style: { zIndex: 7 } },
  { id: 8, style: { zIndex: 8 } },
  { id: 9, style: { zIndex: 9 } },
];
const orderedComps = [
  { id: 7, style: { zIndex: 1 } },
  { id: 8, style: { zIndex: 2 } },
  { id: 9, style: { zIndex: 3 } },
  { id: 1, style: { zIndex: 4 } },
  { id: 2, style: { zIndex: 5 } },
  { id: 3, style: { zIndex: 6 } },
  { id: 4, style: { zIndex: 7 } },
  { id: 5, style: { zIndex: 8 } },
  { id: 6, style: { zIndex: 9 } },
];
const delta = instance.diff(comps, orderedComps);
const undoComps = instance.unpatch(orderedComps, delta);
console.log('isEq', isEqual(undoComps, comps), undoComps)

result

isEq false [
  {"id":1,"style":{"zIndex":4}},
  {"id":2,"style":{"zIndex":1}},
  {"id":3,"style":{"zIndex":3}},
  {"id":4,"style":{"zIndex":4}},
  {"id":5,"style":{"zIndex":8}},
  {"id":6,"style":{"zIndex":5}},
  {"id":7,"style":{"zIndex":7}},
  {"id":8,"style":{"zIndex":6}},
  {"id":9,"style":{"zIndex":9}}
]

[vbarbarosh]

Another piece of code to reproduce the bug:

import * as jsondiffpatch from 'jsondiffpatch';

const a = [
    {uid: 'scene', parent_uid: null},
    {uid: 'txt_clztu14dm00042v6j71u1c9k3', parent_uid: 'scene'},
    {uid: 'grp_cm0vzowcd00022v6izleecn6c', parent_uid: 'scene'},
    {uid: 'txt_cm01a5cpi00012v6inbaunav1', parent_uid: 'grp_cm0vzowcd00022v6izleecn6c'},
    {uid: 'txt_cm097vd9000012v6i9tsfrff2', parent_uid: 'grp_cm0vzowcd00022v6izleecn6c'},
    {uid: 'txt_cm097w3zp00022v6iek5pr7id', parent_uid: 'grp_cm0vzowcd00022v6izleecn6c'},
    {uid: 'fdr_cm0ukrqom00002v6ixqokqydk', parent_uid: 'scene'},
    {uid: 'fdr_cm0umi0e000002v6ivbkyzpwf', parent_uid: 'fdr_cm0ukrqom00002v6ixqokqydk'},
    {uid: 'txt_cm0bc6t0900022v6ij7baxq2d', parent_uid: 'fdr_cm0ukrqom00002v6ixqokqydk'},
    {uid: 'txt_cm0bc70dh00032v6im4wawi5v', parent_uid: 'fdr_cm0ukrqom00002v6ixqokqydk'},
    {uid: 'fdr_cm0vznwt800012v6ial614xz1', parent_uid: 'scene'},
    {uid: 'txt_cm0bc5aid00002v6iu6e4a0m5', parent_uid: 'scene'}
];
const b = [
    {uid: 'scene', parent_uid: null},
    {uid: 'txt_clztu14dm00042v6j71u1c9k3', parent_uid: 'scene'},
    {uid: 'txt_cm01a5cpi00012v6inbaunav1', parent_uid: 'scene'},
    {uid: 'fdr_cm0ukrqom00002v6ixqokqydk', parent_uid: 'scene'},
    {uid: 'fdr_cm0umi0e000002v6ivbkyzpwf', parent_uid: 'fdr_cm0ukrqom00002v6ixqokqydk'},
    {uid: 'txt_cm097vd9000012v6i9tsfrff2', parent_uid: 'fdr_cm0umi0e000002v6ivbkyzpwf'},
    {uid: 'txt_cm097w3zp00022v6iek5pr7id', parent_uid: 'fdr_cm0umi0e000002v6ivbkyzpwf'},
    {uid: 'txt_cm0bc6t0900022v6ij7baxq2d', parent_uid: 'fdr_cm0ukrqom00002v6ixqokqydk'},
    {uid: 'txt_cm0bc70dh00032v6im4wawi5v', parent_uid: 'fdr_cm0ukrqom00002v6ixqokqydk'},
    {uid: 'fdr_cm0vznwt800012v6ial614xz1', parent_uid: 'scene'},
    {uid: 'txt_cm0bc5aid00002v6iu6e4a0m5', parent_uid: 'scene'}
];

const dd = jsondiffpatch.create({
  objectHash: function (item, i) {
    return item.uid || JSON.stringify(item);
  },
});

const diff = dd.diff(a, b);
const c = dd.unpatch(JSON.parse(JSON.stringify(b)), diff);
const cc = unpatch(JSON.parse(JSON.stringify(b)), diff);

console.log(dd.diff(a, c));
console.log(dd.diff(a, cc));

function unpatch(obj, diff)
{
    // 1. Restore property values in obj.
    Object.keys(diff).forEach(function (key) {
        if (key[0] === '_') {
            return;
        }
        unpatch_props(obj[key], diff[key]);
    });
    // 2. Move items to their original positions
    let ii = 0;
    Object.keys(diff).forEach(function (key) {
        const m = key.match(/^_(\d+)$/);
        if (!m || diff[key][2] !== 3) {
            return;
        }
        const i_prev = parseInt(m[1]);
        const i_cur = diff[key][1];
        obj.splice(i_prev - ii, 0, ...obj.splice(i_cur - ii, 1));
        ++ii;
    });
    // 3. Insert removed items
    ii = 0;
    Object.keys(diff).forEach(function (key) {
        const m = key.match(/^_(\d+)$/);
        if (!m || diff[key][2] !== 0) {
            return;
        }
        const i_prev = parseInt(m[1]);
        obj.splice(i_prev - ii, 0, diff[key][0]);
        ++ii;
    });
    return obj;
}

function unpatch_props(obj, props)
{
    Object.keys(props).forEach(function (key) {
        const [prev, cur] = props[key];
        if (obj[key] !== cur) {
            throw new Error('Assertion failed');
        }
        obj[key] = prev;
    });
}

Result:

{
  '5': {
    parent_uid: [
      'grp_cm0vzowcd00022v6izleecn6c',
      'fdr_cm0umi0e000002v6ivbkyzpwf'
    ]
  },
  '6': { parent_uid: [ 'scene', 'grp_cm0vzowcd00022v6izleecn6c' ] },
  _t: 'a'
}
undefined

[vbarbarosh]

It seems that the problem is in reverse: reverse(diff(a, b)) should return the same result as diff(b, a), but results are different.

In other words, unpatch(b, diff(a, b)), which is just patch(b, reverse(diff(a, b)), does not produce a, but patch(b, diff(b, a)) does.

[vbarbarosh]

A temporary solution is to turn off array.detectMove option. That way diffs would be bigger, but unpatch would work correctly:

import * as jsondiffpatch from 'jsondiffpatch';

const a = [
    {uid: 'scene', parent_uid: null},
    {uid: 'txt_clztu14dm00042v6j71u1c9k3', parent_uid: 'scene'},
    {uid: 'grp_cm0vzowcd00022v6izleecn6c', parent_uid: 'scene'},
    {uid: 'txt_cm01a5cpi00012v6inbaunav1', parent_uid: 'grp_cm0vzowcd00022v6izleecn6c'},
    {uid: 'txt_cm097vd9000012v6i9tsfrff2', parent_uid: 'grp_cm0vzowcd00022v6izleecn6c'},
    {uid: 'txt_cm097w3zp00022v6iek5pr7id', parent_uid: 'grp_cm0vzowcd00022v6izleecn6c'},
    {uid: 'fdr_cm0ukrqom00002v6ixqokqydk', parent_uid: 'scene'},
    {uid: 'fdr_cm0umi0e000002v6ivbkyzpwf', parent_uid: 'fdr_cm0ukrqom00002v6ixqokqydk'},
    {uid: 'txt_cm0bc6t0900022v6ij7baxq2d', parent_uid: 'fdr_cm0ukrqom00002v6ixqokqydk'},
    {uid: 'txt_cm0bc70dh00032v6im4wawi5v', parent_uid: 'fdr_cm0ukrqom00002v6ixqokqydk'},
    {uid: 'fdr_cm0vznwt800012v6ial614xz1', parent_uid: 'scene'},
    {uid: 'txt_cm0bc5aid00002v6iu6e4a0m5', parent_uid: 'scene'}
];
const b = [
    {uid: 'scene', parent_uid: null},
    {uid: 'txt_clztu14dm00042v6j71u1c9k3', parent_uid: 'scene'},
    {uid: 'txt_cm01a5cpi00012v6inbaunav1', parent_uid: 'scene'},
    {uid: 'fdr_cm0ukrqom00002v6ixqokqydk', parent_uid: 'scene'},
    {uid: 'fdr_cm0umi0e000002v6ivbkyzpwf', parent_uid: 'fdr_cm0ukrqom00002v6ixqokqydk'},
    {uid: 'txt_cm097vd9000012v6i9tsfrff2', parent_uid: 'fdr_cm0umi0e000002v6ivbkyzpwf'},
    {uid: 'txt_cm097w3zp00022v6iek5pr7id', parent_uid: 'fdr_cm0umi0e000002v6ivbkyzpwf'},
    {uid: 'txt_cm0bc6t0900022v6ij7baxq2d', parent_uid: 'fdr_cm0ukrqom00002v6ixqokqydk'},
    {uid: 'txt_cm0bc70dh00032v6im4wawi5v', parent_uid: 'fdr_cm0ukrqom00002v6ixqokqydk'},
    {uid: 'fdr_cm0vznwt800012v6ial614xz1', parent_uid: 'scene'},
    {uid: 'txt_cm0bc5aid00002v6iu6e4a0m5', parent_uid: 'scene'}
];

const dd = jsondiffpatch.create({
    objectHash: function (item, i) {
        return item.uid || JSON.stringify(item);
    },
    arrays: {
        detectMove: false,
    },
});

const diff = dd.diff(a, b);
const c = dd.unpatch(JSON.parse(JSON.stringify(b)), diff);
console.log(dd.diff(a, c));

[vbarbarosh]

Until pull request will be accepted, fixed versions of reverse and unpatch could be taken from:

• https://github.com/vbarbarosh/jsondiffpatch-helpers/blob/main/src/reverse.js
• https://github.com/vbarbarosh/jsondiffpatch-helpers/blob/main/src/unpatch.js