Routing percent-encoded paths

[mladedav]

• I have looked for existing issues (including closed) about this

Feature Request

Motivation

URIs can be percent-encoded but that should not change what resource is accessed.

More specifically, RFC3986 says:

URIs that differ in the replacement of an unreserved character with
its corresponding percent-encoded US-ASCII octet are equivalent: they
identify the same resource.

There are also some characters that are sometimes encoded and sometimes not in the real world, e.g. hyper will probably have handling of {, }, and " in paths configurable.

Proposal

We can unescape unreserved characters inside the path, which can be decoded at any time. E.g. requests /axum and /%61xum can be interpreted as the same one. We can also normalize reserved characters by percent-encoding them, if they are in the path (with some exceptions that already have special meaning like % , ?, #, and so on; we can however encode {, ", , etc. to normalize these before routing).

We can also encode special characters when registering a route such as internally turning current .route("/100%",..) into .route("/100%25", ...) (%25 is percent encoding for %). Special case of this is that a user can currently write .route("/what?",...) which can never match any request.

With these two changes users can use special characters in route like r#"/"qoutes"/etc"# and match it with both encdoed and not encoded variants.

Alternatives

Using a middleware before axum::Router that decodes (or rather otherwise normalizes) the percent-encoding. Not all percent-decoded paths are valid paths in URI so it would most likely have to percent-decode unreserved characters and percent-encode reserved characters to normalize.

This can be combined with encoding special characters when they are to be registered to matchit (e.g. braces, percent, question mark,...) either by providing something like route_encoded or by having the user encode any needed characters themselves.

I mention this primarily in case we would want to support people who want to have control over percent decoding themselves, but I think this can be also just built inside axum itself.