Awesome
<!--#region:intro-->Regular Expression Pattern Modifiers for ECMAScript
<!--#endregion:intro--> <!--#region:status-->Status
Stage: 3
Champion: Ron Buckton (@rbuckton)
For detailed status of this proposal see TODO, below.
<!--#endregion:status--> <!--#region:authors-->Authors
- Ron Buckton (@rbuckton)
Motivations
One common capability amongst the majority of regular expression engines that is commonly used by parsers, syntax highlighters, and other tools is the capability to control a subset of regular expression flags such as:
i
— Ignore Casem
— Multilines
— Single-line (a.k.a. "dot all")x
— Extended mode (see https://github.com/rbuckton/proposal-regexp-x-mode)
Modifiers are especially helpful when regular expressions are defined in a context where executable code cannot be evaluated, such as a JSON configuration file or TextMate tmLanguage grammar file.
As part of this proposal, we will investigate each existing (and future-proposed) RegExp flag to determine whether they are feasible to used as modifiers.
<!--#endregion:motivations--> <!--#region:prior-art-->Prior Art
See https://rbuckton.github.io/regexp-features/features/modifiers.html for additional information.
<!--#endregion:prior-art--> <!--#region:syntax-->Syntax
Modifiers allow you to change the currently active RegExp flags within a subexpression.
(?imsx-imsx:subexpression)
— Sets or unsets (using-
) the specified RegExp flags for the subexpression.(?imsx-imsx)
— Sets or unsets (using-
) the specified RegExp flags starting at the current position until the next closing)
or the end of the pattern.
NOTE: Certain flags cannot be modified mid-expression. These currently include
g
(global),y
(sticky),u
(unicode), andd
(hasIndices).
NOTE: The actual supported flags will be determined on a case-by-case basis. See #1.
NOTE: This has no conflicts with existing syntax, as ECMAScript currently produces an error for this syntax in both
u
and non-u
modes.
NOTE: The "self-bounded" form (
(?imsx-imsx:subexpression)
) advanced to Stage 2 on December 15th, 2021.
<!--#endregion:syntax--> <!--#region:semantics--> <!-- # Semantics --> <!--#endregion:semantics--> <!--#region:examples-->NOTE: The "unbounded" form (
(?imsx-imsx)
) is no longer being considered as part of this proposal as of December 15th, 2021.
Examples
const re1 = /^[a-z](?-i:[a-z])$/i;
re1.test("ab"); // true
re1.test("Ab"); // true
re1.test("aB"); // false
const re2 = /^(?i:[a-z])[a-z]$/;
re2.test("ab"); // true
re2.test("Ab"); // true
re2.test("aB"); // false
<!--#endregion:examples-->
<!--#region:api-->
<!--
# API
> TODO: Provide description of High-level API.
-->
<!--#endregion:api-->
<!--#region:grammar-->
<!-- # Grammar
```grammarkdown
``` -->
<!--#endregion:grammar-->
<!--#region:references-->
<!-- # References
> TODO: Provide links to other specifications, etc.
* [Title](url) -->
<!--#endregion:references-->
History
- October 27th, 2021 — Proposed for Stage 1 (slides)
- Outcome: Advanced to Stage 1
- December 15th, 2021 — Proposed for Stage 2 (slides)
- Outcome: Advanced to Stage 2 with "self-bounded" form only ("unbounded" form did not advance).
- Stage 2 Reviewers: Richard Gibson, Waldemar Horwat
- June 7th, 2022 — Proposed for Stage 3 (slides)
- Outcome: Advanced to Stage 3
TODO
The following is a high-level list of tasks to progress through each stage of the TC39 proposal process:
Stage 1 Entrance Criteria
- Identified a "champion" who will advance the addition.
- Prose outlining the problem or need and the general shape of a solution.
- Illustrative examples of usage.
-
High-level API.
Stage 2 Entrance Criteria
- Initial specification text.
-
Transpiler support (Optional).
Stage 3 Entrance Criteria
- Complete specification text.
- Designated reviewers have signed off on the current spec text (1 of 2).
- The ECMAScript editor has signed off on the current spec text.
Stage 4 Entrance Criteria
- Test262 acceptance tests have been written for mainline usage scenarios and merged.
- written
- merged
- Two compatible implementations which pass the acceptance tests:
- V8 - Shipping in Chrome 125/Edge 125
- SpiderMonkey - In Progress
- JSC
- Engine262
- A pull request has been sent to tc39/ecma262 with the integrated spec text.
- The ECMAScript editor has signed off on the pull request.