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Item API for "Upgradable"

blizz -> wysłany:
The new S13 Honor gear is Epic yet uses Superior-style Upgrade scheme.

via the Item API, this is unknown:
http://us.battle.net/api/wow/item/91745
{"upgradable": true}

via the Character API, the upgrade information is revealed:
http://us.battle.net/api/wow/character/Suramar/iota?fields=items
{"upgrade": {"current": 0,"total": 2,"itemLevelIncrement": 0}}

I understand that in the game internals, there is an item-by-item specification for how each item should be upgraded but I do not have direct access to that information.

Could the Item API also include an "upgrade" key with "max" (1 or 2) and "itemLevelIncrementStep" (4 or 8) information?
blizz -> wysłany:
Until an item is used in game by a character the upgrade path that it uses is unknown. The logic is done in the game code and is subject to hotfixing and other changes that make it very hard for us if we wanted to duplicate it.

I know this isn't a good answer, but the best way to go about this is to update your knowledge about an items' upgrade ability when you come across profiles with the data in it.