Static property update adds a rogue 'mmsi' property to target path

[preeve9534]

I have a plugin which maintains some paths and I want to add a meta value alongside the data path which describes the path value and its units. So, I want to use static property update.

Before the static update is executed the target key does not exist in the Signal K tree.

I generate a delta expressing the required static update.

var delta = {
  context: 'vessels.urn:mrn:imo:mmsi:235115158.environment.sunphases.dawn',
  updates: [{
    values: [ { "path": "", "value": {
      "meta": { description": "Morning nautical twilight ends, morning civil twilight starts", "units": "ISO-8601 (UTC)" }
    }} ]
  }]
};

And commit it with app.handleMessage.

After the update my path value is:

{
  "mmsi": "235115158",
  "meta": {
    "description": "Morning nautical twilight ends, morning civil twilight starts",
    "units": "ISO-8601 (UTC)"
  }
}

So, the meta property has been added just fine, but where has that pesky 'mmsi' property appeared from?. A ghost in the machine?

[tkurki]

You should use the recently introduced meta deltas for sending metadata.

https://github.com/SignalK/signalk-server/releases/tag/v1.37.0

They've been a long time coming - now the plan is to iron out remaining wrinkles by using this feature and then add them to the specification.

In general the context was originally perceived to work like you've used it. I can't remember the exact details, but supporting arbitrary levels proved to be problematic, and the current implementation assumes that it is fixed to two levels. This is probably not documented as well as it should or at all.

Without testing or looking this up in the code there's most likely logic to fill the mmsi property from contexts with mmsi identity, and it is populated where the context points, thus the rogue property.

The meta delta feature should get you where you want to go, so I am closing this. If there's more to this feel free to reopen.