Nested array issue

[andysCaplin]

Describe the bug
Enumerate the steps to reproduce the bug
Include a small, self-contained example if possible

Given a json document with a nested array value 'names', e.g.

{ "names" : [ "a", "b", "c", "d" ] }
We've noticed that when the document is updated to remove entries in the nested array, for example when removing "c" and "d" above, we're sent a patchDocument that has the following operations:

OperationType:Remove path:"/names/2"
OperationType:Remove path:"/names/3"

This fails as /names/3 is no longer present once 2 is removed.

According to https://tools.ietf.org/html/rfc6902 it should instead read:

OperationType:Remove path:"/names/2"
OperationType:Remove path:"/names/2"

In https://tools.ietf.org/html/rfc6902 it states

Operations are applied sequentially in the order they
appear in the array. Each operation in the sequence is applied to
the target document; the resulting document becomes the target of the
next operation. Evaluation continues until all operations are
successfully applied or until an error condition is encountered.

What compiler, architecture, and operating system?

RedHat Linux 64 bit

What jsoncons library version?

0.153.3

[danielaparker]

I believe jsonpatch::apply_patch works correctly. In your example, the patch should be

[
    {
        "op": "remove",
        "path": "/names/3"
    },
    {
        "op": "remove",
        "path": "/names/2"
    }
]

and applying that patch to the source document does give

{
    "names": ["a", "b"]
}

However, it looks like there is a bug in the function json_patch::from_diff that creates a patch from a source and target document. It looks like it is generating the remove statements in the wrong order.

Daniel

[andysCaplin]

Hi - yes sorry. I transcribed the issue and didn't describe it fully. The remove operations mentioned above are being generated by jsoncons in that order when we apply a patch that removes 2 elements.

[danielaparker]

The issue with jsonpatch::from_diff should be fixed on master. Thanks very much for reporting this. I've added your test to the test cases.

[andysCaplin]

Thanks for the quick fix - when is the next release ?

[danielaparker]

We'll put this into patch release 0.154.2, should be out today or tomorrow.

[danielaparker]

Go with latest 0.154.3, not .2