json8-merge-patch-to-patch

Turn JSON Merge Patch into JSON Patch.

Usage no npm install needed!

<script type="module">
  import json8MergePatchToPatch from 'https://cdn.skypack.dev/json8-merge-patch-to-patch';
</script>

README

JSON8 Merge Patch To Patch

Turn JSON Merge Patch into JSON Patch.

JSON Patch is a more capable alternative to JSON Merge Patch. To work with JSON Patch see JSON8 Patch.

npm install json8-merge-patch-to-patch

const mergePatchToPatch = require("json8-merge-patch-to-patch");

Does not validate the merge patch nor the patch for JSON correctness, use JSON8 valid.

const JSONMergePatch = {
  foo: { bar: "foobar" },
  bar: null,
};
const JSONPatch = mergePatchToPatch(JSONMergePatch);
/*
[
  { op: 'add', path: '/foo/bar', value: 'foobar' },
  { op: 'remove', path: '/bar' }
]
*/

Per specification a JSON Merge Patch that would successfully apply on a document might fail to apply once converted to a JSON Patch.

There are 3 cases:

Incompatible destination

const doc = [];
const JSONMergePatch = { a: "hello" };
const JSONPatch = mergePatchToPatch(JSONMergePatch);
// JSONPatch will fail to apply because doc is not an object

Wrong location

const doc = {};
const JSONMergePatch = { a: { b: "hello" } };
const JSONPatch = mergePatchToPatch(JSONMergePatch);
// JSONPatch will fail to apply because doc.a doesn't exist

Remove non-existant value

const doc = {};
const JSONMergePatch = { a: null };
const JSONPatch = mergePatchToPatch(JSONMergePatch);
// JSONPatch will fail to apply because doc.a doesn't exist

An option could be added to produce a successful JSON Patch no matter what but the only way to do this is to pass the document as well. Let me know if there is any interest or contribute.

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