We currently have four slightly different implementations of transformItem:

• VList
• VDataIterator
• VDataTable
• list-items

and three implementations of "selecting items"

• VDataTable (also used by VDataIterator)
• nested
• list-items (used by VSelect etc but not VList)

list-items is the only one that matches object values fast and correctly (#20937)

• VDataTable still has a O(n²) find() inside map() in transformIn
• VDataTable handles multiple items with the same primitive value but only matches the first item with return-object
• nested uses a Set to store values so only matches objects by reference
  • this has also caused problems when mixing reactive and non-reactive objects: [Bug Report][3.7.7] VTreeview: items as computed property and return-value: not able to open tree #20900
• nested logs a warning if multiple nodes have the same value, and if one is removed from the list then they're all removed from the nodeIds Set
• VDataTable and nested both ignore item-value when return-object is set and use the entire object as a value instead