Bug #13648: [PATCH] Nested map of Enumerator::Lazy with packed values gives wrong result - Ruby master - Ruby Issue Tracking System

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Bug #13648

closed

[PATCH] Nested map of Enumerator::Lazy with packed values gives wrong result

Added by akihikodaki (Akihiko Odaki) over 7 years ago. Updated over 7 years ago.

Status:

Closed

Assignee:

Target version:

ruby -v:

ruby 2.5.0dev (2017-06-09 trunk 59052) [x86_64-linux]

Backport:

2.2: DONTNEED, 2.3: DONTNEED, 2.4: DONE

[ruby-core:81638]

Description

This test case ends up with the following result.

class Step
  include Enumerable
  attr_reader :current, :args

  def initialize(enum)
    @enum = enum
    @current = nil
    @args = nil
  end

  def each(*args)
    @args = args
    @enum.each do |v|
      @current = v
      if v.is_a? Enumerable
        yield *v
      else
        yield v
      end
    end
  end
end

a = Step.new([[1, 2]])
assert_equal([[[1, 2]]], a.lazy.map {|*args| args}.map {|*args| args}.to_a)

<[[[1, 2]]]> expected but was
<[[1, 2]]>.

Here, [[[1, 2]]] is expected because:

An array should be created with the first map, which results in [1, 2].
The array should be wrapped in another array with the second map, which results in [[1, 2]].
The array should be wrapped in another array with to_a, which results in [[[1, 2]]].

However, it returns [[1, 2]] because:

An array will be created with the first map, which results in [1, 2].
However, the array will be internally considered as "packed" and the unpacked arguments will be passed to the second map.
The second map wraps them into another array, which results in [1, 2].
The array will be wrapped in another array with to_a, which results in [[1, 2]].

I have attached the test case and a fix. The fix marks values returned by blocks are not packed.

Files

fix.patch (2.18 KB) fix.patch

A test case and fix

akihikodaki (Akihiko Odaki), 06/09/2017 04:09 PM

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