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Issue #13795 has been updated by davidarnold (David Arnold).
> In the worst case, ruby 3.x may accept backwards-incompatible changes so either way
> I think you can continue to reason in favour of your proposal just fine.
I fully agree that changing Hash#select and #reject (or even #find_all) should not be a 2.x change!
----------------------------------------
Bug #13795: Hash#select return type does not match Hash#find_all
https://bugs.ruby-lang.org/issues/13795#change-66162
* Author: davidarnold (David Arnold)
* Status: Open
* Priority: Normal
* Assignee:
* Target version:
* ruby -v: ruby 2.4.1p111 (2017-03-22 revision 58053) [x86_64-darwin16]
* Backport: 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: UNKNOWN
----------------------------------------
Enumerable#select and Enumerable#find_all are aliases. Hash is_a Enumerable, yet only Hash#select was overridden to return a Hash, with Hash#find_all still returning an Array. This is confusing since the message is that you can use select and find_all interchangeably for Enumerable, yet when you get to Hash, there are warnings that it is no longer true.
Also any code that expects to call select on an Enumerable and get an array back (as documented) could break, but only for Hash#select.
Example:
~~~ ruby
def select_many(*enumerables, &block)
result = []
enumerables.each do |e|
result.concat e.select(&block)
end
result
end
select_many([1, 2], [3, 4]) { |x| x % 2 == 0 } #=> [2, 4]
select_many({ 1 => 2 }, { 3 => 4 }) { |k, v| k < 2 } #=> TypeError: no implicit conversion of Hash into Array
~~~
Should Hash#find_all also return a Hash for consistency? Or, given the fact that calling #to_h on the resulting Array is so easy, should Hash#select revert to the Enumerable behavior of returning an Array?
Proposal 1:
~~~ ruby
h = { "a" => 100, "b" => 200, "c" => 300 }
h.find_all {|k,v| k > "a"} #=> {"b" => 200, "c" => 300}
~~~
Proposal 2:
~~~ ruby
h = { "a" => 100, "b" => 200, "c" => 300 }
h.select {|k,v| k > "a"} #=> [["b", 200], ["c", 300]]
h.select {|k,v| k > "a"}.to_h #=> {"b" => 200, "c" => 300}
~~~
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