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Bug #18971

closed

Enumerator::Lazy.take(0) leaks first element into next operation

Added by Voileexperiments (Library Voile) over 2 years ago. Updated about 2 years ago.

Status:
Closed
Assignee:
-
Target version:
-
ruby -v:
3.0.0p0 (2020-12-25 revision 95aff21468)
Backport:
2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
[ruby-core:109636]

Description

These results with lazy enumerators are as expected:

(2..10).take(0).to_a # => []
(2..10).take(0).map(:&itself).to_a # => []
(2..10).lazy.take(0).to_a # => []

However, once another operation is added after take(0), if first element will pass through directly it will leak through:

(2..10).lazy.take(0).map(&:itself).to_a # => [2]
(2..10).lazy.take(0).select(&:even?).to_a # => [2]
(2..10).lazy.take(0).select(&:odd?).to_a # => []
(2..10).lazy.take(0).reject(&:even?).to_a # => []
(2..10).lazy.take(0).reject(&:odd?).to_a # => [2]
(2..10).lazy.take(0).take(1).to_a # => [2]
(2..10).lazy.take(0).take(0).take(1).to_a # => [2]
(2..10).lazy.take(0).drop(0).to_a # => [2]
(2..10).lazy.take(0).find_all {|_| true}.to_a # => [2]
(2..10).lazy.take(0).zip((12..20)).to_a # => [[2, 12]]
(2..10).lazy.take(0).uniq.to_a # => [2]
(2..10).lazy.take(0).sort.to_a # => []
(2..2).lazy.take(0).sort.to_a # => []

Non lazy versions all return [] as expected.

In 3.1.0 All of them behave as expected as well:

(2..10).lazy.take(0).map(&:itself).to_a # => []
(2..10).lazy.take(0).select(&:even?).to_a # => []
(2..10).lazy.take(0).select(&:odd?).to_a # => []
(2..10).lazy.take(0).reject(&:even?).to_a # => []
(2..10).lazy.take(0).reject(&:odd?).to_a # => []
(2..10).lazy.take(0).take(1).to_a # => []
(2..10).lazy.take(0).take(0).take(1).to_a # => []
(2..10).lazy.take(0).drop(0).to_a # => []
(2..10).lazy.take(0).find_all {|_| true}.to_a # => []
(2..10).lazy.take(0).zip((12..20)).to_a # => []
(2..10).lazy.take(0).uniq.to_a # => []
(2..10).lazy.take(0).sort.to_a # => []
(2..2).lazy.take(0).sort.to_a # => []
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