Duplicate ID in model error during update if parent is changed

I have the following simplified model:

• currentRoot
  • Element A (id XXXX)
  • Element B (id XXXX)
    • Element C (id 96f958fb-d59f-45c4-ae19-c80289d65bff_Block) which is set in the LocalModelSource. Calling “updateModel()” displays the model fine.

I have a operation which removes the hierarchy and produces a flat version of the model which is then set as “currentRoot”. The new model looks like this:

• currentRoot
  • Element A (id XXXX)
  • Element B (id XXXX)
  • Element C (id 96f958fb-d59f-45c4-ae19-c80289d65bff_Block)

Winn update is called i get the following error:

sprotty CommandStack: Failed to execute command: Error: Duplicate ID in model: 96f958fb-d59f-45c4-ae19-c80289d65bff_Block
    at SGraphIndex../node_modules/sprotty/lib/base/model/smodel.js.SModelIndex.add (smodel.ts:224)
    at SGraphIndex../node_modules/sprotty/lib/graph/sgraph.js.SGraphIndex.add (sgraph.ts:191)
    at SGraphIndex../node_modules/sprotty/lib/base/model/smodel.js.SModelIndex.add (smodel.ts:229)
    at SGraphIndex../node_modules/sprotty/lib/graph/sgraph.js.SGraphIndex.add (sgraph.ts:191)
    at SGraph../node_modules/sprotty/lib/base/model/smodel.js.SParentElement.add (smodel.ts:103)
    at update-model.ts:184
    at Object.forEachMatch (model-matching.ts:33)
    at UpdateModelCommand../node_modules/sprotty/lib/features/update/update-model.js.UpdateModelCommand.computeAnimation (update-model.ts:162)
    at UpdateModelCommand../node_modules/sprotty/lib/features/update/update-model.js.UpdateModelCommand.performUpdate (update-model.ts:100)
    at UpdateModelCommand../node_modules/sprotty/lib/features/update/update-model.js.UpdateModelCommand.execute (update-model.ts:88)

Current workaround is something like this at the moment (which is bad because it adds an additional command on stack which needs to be undone):

this.currentRoot.children = [];
await super.updateModel();
this.currentRoot.children = [flat model];

As it looks like the update implementation tries to add the Element C in currentRoot before removing it from Element B first.

[BjBe82]

I can confirm that the fix solves the issue.

[spoenemann]

CC @danieldietrich