ECMA 2018 regex support

[Geobert]

Search Terms

ECMA 2018
lookbehind
regex

Suggestion

Support ECMA 2018 javascript regex

Use Cases

In order to have lookbehind ((?<=) and (?<!)) support

Checklist

My suggestion meets these guidelines:

• [x ] This wouldn't be a breaking change in existing TypeScript / JavaScript code
• [x ] This wouldn't change the runtime behavior of existing JavaScript code
• [x ] This could be implemented without emitting different JS based on the types of the expressions
• [ x] This isn't a runtime feature (e.g. new expression-level syntax)

[mhegazy]

Not sure what is the details of the request here. TypeScript does not do any processing or checking on regular expressions, and they are all deferred to the host. so var x = /(?<=\1(.))/; is already valid TS regular expression.
The compiler does not do any down leveling either for these features, that includes Unicode, and named capture groups.

See #21290 for related discussion

[Geobert]

I've asked for this on VSCode repo and they told me to ask here. So you're saying that extensions in vscode can use lookbehind already?

[mhegazy]

so you want ti use lookbehind in VSCode regexp search box? or in your own .js code?

[Geobert]

I tried to use lookbehind with https://github.com/DomiR/vscode-regreplace and it didn't work

[mhegazy]

I think this is an issue that should go back to VSCode then. TypeScript drives the language service for JS and TS, which is not what we are talking about here.

[octref]

We use ripgrep and seems no: BurntSushi/ripgrep#188

[typescript-bot]

Automatically closing this issue for housekeeping purposes. The issue labels indicate that it is unactionable at the moment or has already been addressed.