kubernetes: strategic patch doesn't keep order of duplicated elements in the list

/kind bug

What happened: given list with duplicated keys D1

mergingList:
 - name: D1
   value: URL1
 - name: A
   value: x
 - name: D1
   value: URL2

and a patch updating non-duplicated key A:

$setElementOrder/mergingList:
 - name: D1
 - name: A
 - name: D1
mergingList:
 - name: A
   value: z

it reorders keys:

mergingList: 
 - name: D1
   value: URL1
 - name: D1
   value: URL2
 - name: A
   value: z

What you expected to happen:

Order of duplicated keys stays the same

mergingList: 
 - name: D1
   value: URL1
 - name: A
   value: z
 - name: D1
   value: URL2

How to reproduce it (as minimally and precisely as possible):

I created test-case which fails on release-1.10 and master: https://github.com/redbaron/kubernetes/commit/971c1b20e51dd2090a9fd585bafa18282c2984f5

Anything else we need to know?:

I am trying to find out why kubectl creates incorrect patch on apply. Although I can’t reproduce it with a simple test case like in this ticket, it look related to it. On a real resource kubectl apply it reorders keys in generated patch, so it generates something like:

$setElementOrder/mergingList:
 - name: D1
 - name: A
 - name: D1
mergingList:
 - name: D1
   value: URL1
 - name: D1
   value: URL2
 - name: A
   value: z

which makes it an invalid patch as order of keys differs from order of values. This reordering might or might not be result of the same underneath bug.

/sig api-machinery