Bug #11808: Different behavior between Enumerable#grep and Array#grep - Ruby master - Ruby Issue Tracking System

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Bug #11808

open

Different behavior between Enumerable#grep and Array#grep

Added by BenOlive (Ben Olive) over 7 years ago. Updated over 2 years ago.

Status:

Open

Priority:

Normal

Assignee:

ko1 (Koichi Sasada)

Target version:

ruby -v:

Backport:

2.5: UNKNOWN, 2.6: UNKNOWN

[ruby-core:72067]

Tags:

core

Description

Regex special global variables are available within the block for Array#grep, but are nil within the block for Enumerable#grep.

Here is an example that explains it better:

class Test
  include Enumerable
  def each
    return enum_for(:each) unless block_given?
    yield "Hello"
    yield "World"
  end
end

enum = Test.new
array = ["Hello", "World"]

enum.grep(/^(.)/) {$1} # => [nil, nil]
array.grep(/^(.)/) {$1} # => ["H", "W"]

Tested on 2.0.0, 2.1.5, & 2.2.2

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#1 [ruby-core:93397]

Updated by jeremyevans0 (Jeremy Evans) almost 4 years ago

Array#grep is actually Enumerable#grep:

Array.instance_method(:grep).owner
=> Enumerable

If I had to guess, the cause of the difference is that Array#each is implemented in C, and Test#each is implemented in Ruby, and this affects Regexp special variable scope. You see similar behavior as Array in other classes that implement #each in C, such as Range or File.

The documentation for the special global variables states: These global variables are thread-local and method-local variables. This indicates to me that the bug is that the variables are accessible inside the Array#each block, since that block executes inside the current method, it's not local to the Array#each method. However, I would assume removing the current behavior would break too much existing code.

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#2 [ruby-core:93422]