Add ECClass in frontend txnentitychanges

[FelixGirard]

Is your feature request related to a problem? Please describe.

We have a lot of frontend related to elements. We have a lot of onElementsChanged handlers in the frontend.
For example, for custom manipulators.
Most of them only apply to certain classes.
Currently they query for the props and then filter, but that is not efficient or scalable.

Describe the solution you'd like

I would like the txnentitychanges from the frontend to have the ECClass, like EntityIdAndClassName.

Describe alternatives you've considered

Right now we are querying the props in each handler.

[bsy-nicholasw]

Seconded.

The backend has all this context and just throws it away for the frontend notification. Having only the ID and no class ID at least makes editing cases more painful to handle.

And to be clear, on the frontend for ECClassId to be resolved to ECClassName.

[khanaffan]

The current way is to iterate and go through metadata:

iModel.txns.onElementsChanged.addListener((changes: TxnEntityChanges) => {

  // 1. Exact class match
  for (const change of changes) {
    if (change.metadata.classFullName === "MySchema:MyElement") {
      console.log(change.id, change.type);
    }
  }

  // 2. Class hierarchy check (e.g. "is this a GeometricElement or subclass?")
  for (const change of changes.filter({
    includeMetadata: (m) => m.is("BisCore:GeometricElement")
  })) {
    console.log(change.id, change.metadata.classFullName);
  }

  // 3. Filter by both class AND change type
  for (const change of changes.filter({
    includeTypes: ["inserted"],
    includeMetadata: (m) => m.is("BisCore:GeometricElement")
  })) {
    console.log(change.id);
  }
});

The issue is that change.metadata.classFullName is not obvious — users don't know it's there without reading the docs closely, so they fall back to fetching element props via RPC just to get the class name.

How we can make it more discoverable?

Here are the proposed changes:

Add classFullName to the TxnEntityChange interface:

export interface TxnEntityChange {
  type: TxnEntityChangeType;
  id: Id64String;
  /** The entity's ECClass in "Schema:Class" format. Shortcut for `metadata.classFullName`. */
  classFullName: string;
  metadata: TxnEntityMetadata;
}

@FelixGirard do you want me to improve usability by added classFullName or you good with our current implementation. It clearly difficult to discover but it does not need addition RPC call. The fix also can be done in compatible way.

[FelixGirard]

Seems exactly like what I was asking for! Wasn't so obvious but it is what I needed.
Thanks! :)

In the future I think your proposal would be a good improvement.

You can close this or use it for the improvement, your call.