"path must be" (regex) syntax in v8 (i18n/localization)

[samuelstroschein]

Hi there,

I am wondering how path-to-regexp would support matching paths "only if" or whether I need to adopt URLPattern.

Use case i18n

I need a pattern that matches localized URLs.

https://example.com/page -> en
https://example.com/de/page -> de

The pattern I came up with "http{s}\\://:domain/{:locale}{/*path}" (correctly) matches anything as :locale. Hence, https://example.com/page is matched as parameters: { locale: page }, which is incorrect. The desired locale parameter should be undefined.

In old path-to-regexp <8 and URLPattern, regex helps establish the desired behavior (try it out yourself).

http{s}?://:domain.:tld/:locale(de)?/:path*

[samuelstroschein]

I decided to adopt URLPattern now that it has become the standard for the web.

• Safari implemented URLPattern this week
• NodeJS implemented URLPattern this week
• URLPattern got on the interop 2025 list this week.

[blakeembrey]

Sounds good. URLPattern is based off the v6 syntax of this library anyway so it should be a smooth transition for you.

In v8 there currently isn't regex support due to time constraints, but it would actually be fairly simple to add what you're asking for specifically (i.e. a limited subset of regex support). I'll leave this closed since you've resolved your issue, but it is on my backlog to add regex support back so you can write :locale(de|en) again.