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https://github.com/tc39/proposal-regexp-r-escape
Regular Expression `\R` Escape for ECMAScript
https://github.com/tc39/proposal-regexp-r-escape
Last synced: 2 months ago
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Regular Expression `\R` Escape for ECMAScript
- Host: GitHub
- URL: https://github.com/tc39/proposal-regexp-r-escape
- Owner: tc39
- License: bsd-3-clause
- Created: 2021-10-15T20:59:08.000Z (about 3 years ago)
- Default Branch: main
- Last Pushed: 2021-12-04T02:51:21.000Z (about 3 years ago)
- Last Synced: 2024-08-04T04:02:44.882Z (5 months ago)
- Language: HTML
- Homepage: https://tc39.es/proposal-regexp-r-escape
- Size: 190 KB
- Stars: 5
- Watchers: 6
- Forks: 2
- Open Issues: 2
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# Regular Expression `\R` Escape for ECMAScript
## Status
**Stage:** 1
**Champion:** Ron Buckton ([@rbuckton](https://github.com/rbuckton))
_For detailed status of this proposal see [TODO](#todo), below._
## Authors
* Ron Buckton ([@rbuckton](https://github.com/rbuckton))
# Motivations
> NOTE: See https://github.com/rbuckton/proposal-regexp-features for an overview of
> how this proposal fits into other possible future features for Regular Expressions.
The `\R` escape sequence matches the various sets of code points that match a unicode line terminator, which can be difficult to write correctly.
# Prior Art
* [Perl](https://rbuckton.github.io/regexp-features/engines/perl.html#feature-line-endings-escape)
* [PCRE](https://rbuckton.github.io/regexp-features/engines/pcre.html#feature-line-endings-escape)
* [Boost.Regex](https://rbuckton.github.io/regexp-features/engines/boost.regex.html#feature-line-endings-escape)
* [Oniguruma](https://rbuckton.github.io/regexp-features/engines/oniguruma.html#feature-line-endings-escape)
* [ICU](https://rbuckton.github.io/regexp-features/engines/icu.html#feature-line-endings-escape)
* [Glib/GRegex](https://rbuckton.github.io/regexp-features/engines/glib-gregex.html#feature-line-endings-escape)
See https://rbuckton.github.io/regexp-features/features/line-endings-escape.html for additional information.
# Syntax
- `\R` — Matches any line ending character sequence.
> NOTE: Requires the `u` or `v` flags, as `\R` is currently just an escape for `R` without the `u` flag.
> NOTE: Not supported inside of a character class.
# Semantics
- In `u` or `v` mode, `\R` is roughly equivalent to the following pattern:
```re
(?>\r\n?|[\x0A-\x0C\x85\u{2028}\u{2029}])
```
- Aligns with `^` and `$` in `mu` mode
- When not in `u` or `v` mode, `\R` will continue to match the literal character `R`.
> NOTE: The above example uses atomic groups `(?>)` to prevent backtracking when matching `\r\n?`. Atomic groups is proposed [here](https://github.com/rbuckton/proposal-regexp-atomic-operators).
# Examples
```js
// split lines regardless of line termiantor style
const lines = fs.readFileSync("file.txt", "utf8").split(/\R/ug);
```
# History
- October 28, 2021 — Proposed for Stage 1 ([slides](https://1drv.ms/p/s!AjgWTO11Fk-TkfoQmhSpEYYM0spVqg?e=zsP6g4))
- Outcome: Advanced to Stage 1
# TODO
The following is a high-level list of tasks to progress through each stage of the [TC39 proposal process](https://tc39.github.io/process-document/):
### Stage 1 Entrance Criteria
* [x] Identified a "[champion][Champion]" who will advance the addition.
* [x] [Prose][Prose] outlining the problem or need and the general shape of a solution.
* [x] Illustrative [examples][Examples] of usage.
* [ ] ~~High-level [API][API].~~
### Stage 2 Entrance Criteria
* [x] [Initial specification text][Specification].
* [ ] ~~[Transpiler support][Transpiler] (_Optional_).~~
### Stage 3 Entrance Criteria
* [ ] [Complete specification text][Specification].
* [ ] Designated reviewers have [signed off][Stage3ReviewerSignOff] on the current spec text.
* [ ] The ECMAScript editor has [signed off][Stage3EditorSignOff] on the current spec text.
### Stage 4 Entrance Criteria
* [ ] [Test262](https://github.com/tc39/test262) acceptance tests have been written for mainline usage scenarios and [merged][Test262PullRequest].
* [ ] Two compatible implementations which pass the acceptance tests: [\[1\]][Implementation1], [\[2\]][Implementation2].
* [ ] A [pull request][Ecma262PullRequest] has been sent to tc39/ecma262 with the integrated spec text.
* [ ] The ECMAScript editor has signed off on the [pull request][Ecma262PullRequest].
[Process]: https://tc39.es/process-document/
[Proposals]: https://github.com/tc39/proposals/
[Grammarkdown]: http://github.com/rbuckton/grammarkdown#readme
[Champion]: #status
[Prose]: #motivations
[Examples]: #examples
[API]: #api
[Specification]: https://tc39.es/proposal-regexp-r-escape
[Transpiler]: #todo
[Stage3ReviewerSignOff]: #todo
[Stage3EditorSignOff]: #todo
[Test262PullRequest]: #todo
[Implementation1]: #todo
[Implementation2]: #todo
[Ecma262PullRequest]: #todo