From: janosch-x via ruby-core <ruby-core@...>
Date: 2023-05-30T18:03:55+00:00
Subject: [ruby-core:113704] [Ruby master Feature#19694] Add Regexp#timeout= setter

Issue #19694 has been updated by janosch-x (Janosch M�ller).





I guess the only noteworthy argument for a change goes like this:

 

A custom `timeout` only being available on `Regexp::new` might lead people to write less performant code.



I'm not sure this is a strong argument. The big Regexps that take a noteworthy time to compile are often those with interpolation, as seen in the OP, and I assume these aren't so easy to pre-compile or deduplicate anyway.



Maybe there could be an instance method, `Regexp#with_timeout`, that creates *and memoizes* a copy with a specific timeout? This also sounds a bit hacky, though...



----------------------------------------

Feature #19694: Add Regexp#timeout= setter

https://bugs.ruby-lang.org/issues/19694#change-103350



* Author: aharpole (Aaron Harpole)

* Status: Open

* Priority: Normal

----------------------------------------

# Abstract



In addition to allowing for a Regexp timeout to be set on individual instances by setting a `timeout` argument in `Regexp.new`, I'm proposing that we also allow setting the timeout on Regexp objects with a `#timeout=` setter.



# Background



To be able to roll out a global Regexp timeout for a large application, there are inevitably some individual regexes for which a different timeout is appropriate. While the `timeout` keyword argument was added to `Regexp.new`, this isn't always a viable option.



In the case of regex literal syntax (`/ab*/` or `%r{ab*}`, for instance), it's not possible to set a timeout at all right now without converting to `Regexp.new`, which may be awkward depending on the contents of the regex.



It also is desirable from time to time to be able to set a timeout for a regex object after it's been initialized.



Finally, because we offer a `Regexp#timeout` getter, for consistency it would be nice to also offer a setter.



The introduction of a `Regexp#timeout=` setter was mentioned as a possible way to set individual timeouts in https://bugs.ruby-lang.org/issues/19104#Specification.



# Proposal



I propose that we add the method `Regexp#timeout=`. It works the same way the `timeout` argument works in `Regexp.new`, taking either a float or nil.



This makes it relatively easy to add timeouts to specific regex literals (regex literals are frozen by default so you do have to `dup` them first):



```

emoji_filter_pattern = %r{

  (?<!#{Regexp.quote(ZERO_WIDTH_JOINER)})

  #{EmojiFilter.unicodes_pattern}

  (?!#{Regexp.union(EmojiFilter::MODIFIER_CHAR_MAP.keys.map { |k| Regexp.quote k })})

}x.dup

emoji_filter_pattern.timeout = 1.0

emoji_filter_pattern.freeze

```



# Implementation



This setter has been implemented in https://github.com/ruby/ruby/pull/7847.



# Evaluation



It's just a setter, so pretty straightforward in terms of implementation and use.



# Discussion



It's worth considering other options for overriding `Regexp.timeout`. I'd love to see something like the following for overriding regexp timeouts as well:



```

Regexp.timeout = 1.0



Regexp.with_timeout(5.0) do

  evaluate_slower_regexes

end

```



It's possible to implement something like `Regexp.with_timeout` but it's not thread-safe by default since it would involve overwriting `Regexp.timeout`.



# Summary



Regexp instances have a getter for timeout, and adding a corresponding setter adds consistency and will make it easier for developers to adopt adding a global `Regexp.timeout` by making it simpler to adjust timeouts on a regex by regex basis.



It's a minor change but the added consistency and flexibility help us optimize for developer happiness.







-- 

https://bugs.ruby-lang.org/

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