From: "sam.saffron (Sam Saffron)" <sam.saffron@...>
Date: 2013-04-12T12:06:14+09:00
Subject: [ruby-core:54209] [ruby-trunk - Feature #8110] Regex methods not changing global variables


Issue #8110 has been updated by sam.saffron (Sam Saffron).


Has anyone given any thought at how to make this friendly with older versions of Ruby ... say I have 

def is_foo?(val)
  val =~ /foo/
end

And now I want this code to work in both 1.9.3 and master. 

# ugly and slow
def is_foo?(val)
  if defined? Regexp::SKIP_GLOBALS
    val =~ /foo/G
  else 
    val =~ /foo/
  end
end


# will not work on 1.9.3
def is_foo?(val)
   val =~ /foo/G
end
 

# could work, risky perf 
def is_foo?(val)
  val =~ _G(/foo/)
end

# least horribly imho
IS_FOO = _G(/foo/)
def is_foo?(val)
  val =~ IS_FOO
end

--- 

So I wonder, is the plan to backport this? Are there any other ways to keep code compatible and clean? 
  
----------------------------------------
Feature #8110: Regex methods not changing global variables
https://bugs.ruby-lang.org/issues/8110#change-38482

Author: prijutme4ty (Ilya Vorontsov)
Status: Assigned
Priority: Normal
Assignee: matz (Yukihiro Matsumoto)
Category: core
Target version: next minor


It is useful to have methods allowing pattern matching without setting global variables. It can be very hard to understand where the problem is when you for example insert a string like `puts pat === my_str` and your program fails in a place which is far-far away from inserted place. This can happen due to replacing global variables of previous pattern match. I caught to this when placed pattern-match inside case-statement and shadowed global vars which were initially filled by match in when-statement.
For now one can extract pattern matching into another method thus defining method-scope for that variables. But sometimes it looks like an overkill. May be simple method like #match_globalsafe can prevent that kind of errors. At least when a programmer see such a method in a list of methods, he's warned that usual match can cause such problems.


-- 
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