Make extractors with Infallible rejection type more convenient

[jplatte]

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

Feature Request

Motivation

Some extractors such as CookieJar use an Infallible rejection type. Currently, one has to use .unwrap() / .expect("infallible") / .unwrap_or_else(|i| match i {}) after the actual extraction function call to get rid of it.

Proposal

• Add RequestPartsExt::extract_infallible (and extract_infallible_with_state RequestExt::extract_parts_infallible, ...) for 0.7.x
• Consider renaming current extract methods on the extension traits to try_extract and removing the _infallible suffix for 0.8.x

Alternatives

• Provide our own ResultExt with our own variant of Result::into_ok.

Open questions

Are body extractors ever infallible / does it make sense to provide RequestExt::extract_infallible?

[mladedav]

Are body extractors ever infallible / does it make sense to provide RequestExt::extract_infallible?

Body itself is infallible as it pretty much just provides the underlying stream. Anything that actually collects the bytes would be fallible though. I don't think it makes much sense to add extract_infallible for that case though.

But it does make sense to me for request parts.

[ItsEthra]

I think this can be closed now since in the 1.82 you can just match the result with infallible https://blog.rust-lang.org/2024/10/17/Rust-1.82.0.html#omitting-empty-types-in-pattern-matching.