From: merch-redmine@...
Date: 2021-07-27T19:35:52+00:00
Subject: [ruby-core:104711] [Ruby master Bug#14500] Missing Regexp documentation and clarification on behavior of \K for edge case

Issue #14500 has been updated by jeremyevans0 (Jeremy Evans).


Sundeep (Sundeep Agarwal) wrote:
> **Anchors** section (https://ruby-doc.org/core-2.5.0/Regexp.html#class-Regexp-label-Anchors)
> 
> * suggestion to add documentation on `\K`
> * need clarification if the below behavior seen is expected and mention it while adding documentation
> 
> ```
> $ echo 'aaa' | ruby -pe 'gsub(/a\K/, ":")'
> a:aa:
> 
> $ # what I expected
> $ echo 'aaa' | ruby -pe 'gsub(/(a)/, "\\1:")'
> a:a:a:
> ```

The `\K` behavior at the end of a regexp is a bug that has already been filed upstream in Onigmo: https://github.com/k-takata/Onigmo/issues/152

I agree about the other documentation issues, and I'll push a commit shortly to address them.

----------------------------------------
Bug #14500: Missing Regexp documentation and clarification on behavior of \K for edge case
https://bugs.ruby-lang.org/issues/14500#change-93037

* Author: Sundeep (Sundeep Agarwal)
* Status: Open
* Priority: Normal
* Backport: 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN
----------------------------------------
**Capturing** section (https://ruby-doc.org/core-2.5.0/Regexp.html#class-Regexp-label-Capturing)

* formatting issue: `n<sup>th</sup>`
* suggestion to add a note on `\0` similar to the note mentioned in **Special global variables** (https://ruby-doc.org/core-2.5.0/Regexp.html#class-Regexp-label-Special+global+variables) section about `$&`
* suggestion to add that numbered capturing groups is limited to `9`

**Anchors** section (https://ruby-doc.org/core-2.5.0/Regexp.html#class-Regexp-label-Anchors)

* suggestion to add documentation on `\K`
* need clarification if the below behavior seen is expected and mention it while adding documentation

```
$ echo 'aaa' | ruby -pe 'gsub(/a\K/, ":")'
a:aa:

$ # what I expected
$ echo 'aaa' | ruby -pe 'gsub(/(a)/, "\\1:")'
a:a:a:
```




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