Optional params/zero-length rest routes

Via this Stack Overflow question. It would be nice if there was a way to do optional parameters — e.g. /foo, /fr/foo and /ca/fr/foo all resolving to the same page component (where fr is a named lang parameter and ca is a named country parameter).

@Timer from the Next.js team had a neat idea — we could mark optional parameters with double brackets: routes/[[country]]/[[lang]]/foo.svelte

At the same time, it might be nice if routes/[...parts]/foo.svelte matched all those pathnames. At present it will match /fr/foo and /ca/fr/foo but not /foo.

[antony]

I absolutely want this. It would simplify my search pages significantly - filesystem routes are not ideal for SEO!

I just tested this on my filesystem and it does seem to work - but it’s not extensive, obviously!

/routes/[country?]/[lang?]/foo.svelte

[antony]

@jhwheeler my own approach at this time would be to open a RFC, link all of these issues, and detail:

1. The new route options you would like to see
2. Alternatives for mapping syntax
3. The proposed syntax for those route changes
4. A part on how breaking this is in terms of people’s existing codebase
5. OS compatibility (Windows / Linux / Mac)

I think from there you’d be in a good position to gather any required feedback, resistance, etc, in order to create a PR to add the syntax.