[netconf] Clarification about RFC8040 plain PATCH operation

[Henning Rogge <[e-mail]>]

Hi,

I have trouble making sure I get the meaning of the RFC8040 plain
Patch operation right... mostly because of the (potential) double
meaning of the word "merge".

Is the plain patch operation meant as a shallow merge or a deep merge?

Here is my attempt as an example with a PATCH operation of the node "rootC".

YANG context:
container rootC {
        container partA {
                leaf leafA1 {
                        type string;
                }
                leaf leafA2 {
                        type string;
                }
        }
        container partB {
                leaf leafB1 {
                        type string;
                }
                leaf leafB2 {
                        type string;
                }
        }
}

Datastore content before the PATCH operation:
{
        "ns:rootC": {
                "partA": {
                          "leafA1": "A1",
                          "leafA2": "A2"
                },
                "partB": {
                          "leafB1": "B1",
                          "leafB2": "B2"
                }
        }
}

Simple Patch Body:
{
        "ns:rootC": {
                "partA": {
                          "leafA1": "newA1",
                }
        }
}

Datastore content after PATCH with "shallow" merge:
{
        "ns:rootC": {
                "partA": {
                          "leafA1": "newA1",
                },
                "partB": {
                          "leafB1": "B1",
                          "leafB2": "B2"
                }
        }
}

Datastore content after PATCH with "deep/recursive" merge:
{
        "ns:rootC": {
                "partA": {
                          "leafA1": "newA1",
                          "leafA2": "A2"
               },
                "partB": {
                          "leafB1": "B1",
                          "leafB2": "B2"
                }
        }
}

With a shallow merge, the merging is only done for the
root-container... with the deep merge the server has to recursively go
down each patched container.

Henning Rogge