Rendering partial over collection with cached: true leave out same items

[foton]

Steps to reproduce

I have view with:

<% same_sets = [
  [1,2,3,4,5],
  [1,2,3,4,5],
  [1,2,3,4,4],
  [1,2,3,4,4],
  [1,2,3,4,6],
]%>
with 'cached: true'<br />
<%= render partial: 'test_row', collection: same_sets, cached: true %>
<br />
with 'cached: false'<br />
<%= render partial: 'test_row', collection: same_sets, cached: false %>
<br />

and corresponding partial _test_row.html.erb :

<%= test_row.first %> | <%= test_row.second %> | <%= test_row.third %> | <%= test_row.fourth %> | <%= test_row.fifth %><br />

That view will produce this result:

with 'cached: true'
1 | 2 | 3 | 4 | 5
1 | 2 | 3 | 4 | 4
1 | 2 | 3 | 4 | 6

with 'cached: false'
1 | 2 | 3 | 4 | 5
1 | 2 | 3 | 4 | 5
1 | 2 | 3 | 4 | 4
1 | 2 | 3 | 4 | 4
1 | 2 | 3 | 4 | 6

Expected behavior

For array with size 5, I expect 5 rows, with or without caching.

Actual behavior

For array with size 5, I got 3 (different) rows with caching enabled.

System configuration

Rails version: 5.2.2

Ruby version:
2.4.1p111 (2017-03-22 revision 58053) [x86_64-linux]

[st0012]

I think this is a bug and I can reproduce it in latest master as well.

[y-yagi]

Fixed by #35145