Centralize isConnection, isLabel and isRoot Checks

[philippfromme]

• export isConnection, isLabel and isRoot checks from ModelUtil and test
• use these checks
• checks will be usable by bpmn-js, too

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Required by bpmn-io/bpmn-js#1903
Related to bpmn-io/bpmn-js#1901

[philippfromme]

@nikku When fixing bpmn-io/bpmn-js#1901 I tried this approach. I'd vote for using actual instanceof checks whenever possible and using is*Like checks when not (eg. CopyPaste). Let me know what you think.

[nikku]

What is the benefit of instanceof over proper structural checking (i.e. 'labelTarget' in someObject) that we did in the past? The later works in both instance checks as well as is*Like contexts.

[philippfromme]

'labelTarget' in someObject

My first idea was using Object.hasOwn(label, 'labelTarget'). But this still doesn't prevent bugs like bpmn-io/bpmn-js#1902. The respective test doesn't work because the connection is created without waypoints. Checking for instanceof would prevent that.

[philippfromme]

As discussed with @nikku I will use Object.hasOwn instead of instanceof as it can lead to issues when dealing with more than one instance of diagram-js.

[nikku]

@philippfromme min-dash has you covered .

[nikku]

Why would we rename this?

[philippfromme]

We don't have to. One thing I was wondering about is the fact we use this check in Modeling. Doesn't that have the same issue with having more than one diagram-js?

[nikku]

Yes, it does. However it was never a problem to date. A safe way is to rather do the check in the elementFactory, hence my prior attempt to move it there.

[philippfromme]

Reverted.

[nikku]

Good stuff.