Problem of Object equality checks with frozen objects

[Cito]

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Plunkr Case (Bug Reports)
http://plnkr.co/jCwS5OadJK7KHP0wptat

Current behavior
When you load data via the Apollo GraphQL client and use it for a selectable DataTable that has no dataKey set, you get an error "Cannot add property _$visited, object is not extensible" when selecting rows.

Expected behavior
There should be no error, like with data loaded from other sources or when setting a dataKey.

Minimal reproduction of the problem with instructions
see Plunkr case above

What is the motivation / use case for changing the behavior?
I want to display data loaded with the Apollo Client for GraphQL directly in a PrimeNG DataTable.

• Angular version: 5.0.5

• PrimeNG version: 5.0.2

• Browser: Chrome, Edge, Firefox

• Language: TypeScript 2,4

Analysis of the Problem:

The problem is caused by Apollo Client returning "deep-frozen" query results in test and development. Particularly, no new properties can be added to these objects.

However, when there is no dataKey set on a DataTable, PrimeNG tries to compare rows using its objectUtils.equals() method. This method tries to set a _$visited property on the examined objects, which does not work when the objects are frozen.

[cagataycivici]

Thank you.