[ruby-core:107100] [Ruby master Bug#18486] Enumerable#group_by ordering appears to have changed and doesn't match docs.

Issue #18486 has been updated by jeremyevans0 (Jeremy Evans).


This is only a minor documentation issue.  I assume the documentation is a left over from pre-1.9, when hashes were unordered.  I'll fix it.

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Bug #18486: Enumerable#group_by ordering appears to have changed and doesn't match docs. 
https://bugs.ruby-lang.org/issues/18486#change-95946

* Author: [e-mail] (kay rhodes)
* Status: Open
* Priority: Normal
* ruby -v: 3.0.2
* Backport: 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
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The documentation for Enumerable#group_by suggests the following:

(1..6).group_by { |i| i%3 }   #=> {0=>[3, 6], 1=>[1, 4], 2=>[2, 5]}

it actually produces this (same values different order). Tested in 2.6.3 and 3.0.2

(1..6).group_by { |i| i%3 }   #=> {1=>[1, 4], 2=>[2, 5], 0=>[3, 6]}

as hash table ordering is something people depend on these days I wonder if the reordering of the keys may be more than just a minor documentation bug. 

I noticed this in 2.6.3. Assuming the docs matched reality when written this implies we've been living with this for a while. I don't know how long before that this actually changed. 



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