feat(router): add req.params type-safety via string patterns;

[lukeed]

Shoutout to @dummdidumm for reminding me!

TypeScript Playground

Note: There's still a TODO for wildcard patterns (/foo/*, /:foo/*, /:foo/*/:bar) but this can come later.

[dummdidumm]

Thanks for the shoutout 😄

Regarding the TODO: I solved it this way: Playground

type RouteParams<T extends RoutePattern> =
	T extends `${infer Prev}/*/${infer Rest}`
		? { wild: string } & RouteParams<Prev> & RouteParams<Rest>
  : T extends `${string}:${infer P}?/${infer Rest}`
		? { [K in P]?: string } & RouteParams<Rest>
  : T extends `${string}:${infer P}/${infer Rest}`
		? { [K in P]: string } & RouteParams<Rest>
  : T extends `${string}:${infer P}?`
		? { [K in P]?: string }
  : T extends `${string}:${infer P}`
		? { [K in P]: string }
  : T extends `${string}*`
		? { wild: string }
  : {};

Changes are

• remove the unnecessary infers and replace it with {string}
• for the wildcard, do a recursion before and after the /*/. Problem is, if you don't do this, TS will just go greedy up until the first * and discard everything before that. This fixes the missing foo comments in the Playground
• make the optional param recursion the same as the one with required params, not sure why it was like this in the original Playground. This fixes the baz must be baz? comment

[lukeed]

@dummdidumm This is awesome!! Thanks!
TIL that {string} can be used for inference. Dunno why never tried that 😅