Feature #10482: Allow ignored items to vary in `Enumerable#chunk`.

• Status: Feedback
• Priority: Normal
• Assignee: -
• Target version: -

[sawa (Tsuyoshi Sawada)]

In #5663, regarding a method proposed, Yehuda Katz's writes:

The only caveat is that it would be impossible to intentionally return nil here; suggestions welcome.

I would like to note here that the same problem exists with Enumerable#chunk. Currently, when the key value is nil, the corresponding items are thrown out. That may be useful sometimes, but sometimes, silently doing so causes a hard-to-detect bug. At least, there should be a way to change what is ignored (which would not break existing code using it), and ideally, nothing should be thrown out unless explicitly specified (which would break existing code).

I propose Enumerable#chunk to take an optional named parameter ignore, which switches what is ignored. When something other than nil is specified, then nil should not be ignored:

[:foo1, :foo2, "bar", nil, nil].chunk(ignore: String){|e| e.class}
# => [[Symbol, [:foo1, :foo2]], [NilClass, [nil, nil]]]

When you don't want anything to be ignored, then the parameter should be set to something that does not appear in the receiver:

[:foo1, :foo2, "bar", nil, nil].chunk(ignore: "nothing to ignore"){|e| e.class}
# => [[Symbol, [:foo1, :foo2]], [String, ["bar"]], [NilClass, [nil, nil]]]

[sawa (Tsuyoshi Sawada)]

Sorry, the example was wrong; I mistook nil and NilClass. But I hope you get the point.

[akr (Akira Tanaka)]

• Status changed from Open to Feedback

The method has a form which is incompatible with your proposal: enum.chunk(initial_state) { |elt, state| ... }

However I deprecated the form (since Ruby 2.2), your porposal may be considerable in future.