[ruby-core:59269] [ruby-trunk - Feature #9270] Array#to_h should not ignore badly formed elements

Issue #9270 has been updated by naruse (Yui NARUSE).


OK, could you commit it?
I'll backport it to ruby_2_1 branch.
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Feature #9270: Array#to_h should not ignore badly formed elements
https://bugs.ruby-lang.org/issues/9270#change-43829

Author: marcandre (Marc-Andre Lafortune)
Status: Open
Priority: Urgent
Assignee: naruse (Yui NARUSE)
Category: core
Target version: current: 2.1.0


The upcoming Array#to_h feature currently ignores elements that are not 2-elements arrays. Array#to_h could instead raise an error on those elements. I argued otherwise before, but maybe that would be safer.

One reason I think I was wrong is that current form could encourage code like:

  enum.map{|x| [x.foo, x.bar] if x.baz? }.to_h

using the fact that any `nil` will be ignored. I'm not sure that it's a good idea.

It would probably be safer to raise an Exception for elements that are not a key-value pair. It also satisfies fail-early principle.

@sawa agrees with this.
@matz agrees with the change.

Since this feature has not already been released in an official version, changing this behavior now would not cause any incompatibility and there should be no risk of regression. Changing this feature after the official 2.1 release would be more problematic as it could cause incompatibilities.

Yui, could you please confirm that there is no problem on your end for me to commit the following patch: https://github.com/marcandre/ruby/compare/to_h_raise


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