Add Method::from_static

[WhyNotHugo]

Allows creating constant Method instances, e.g.:

const PROPFIND: Method = Method::from_static(b"PROPFIND");

Fixes: #587

[WhyNotHugo]

Oh, I just realised that CI failed due to panic! not being available on the MSRV. I'll try refactoring that.

[seanmonstar]

We could probably update the MSRV, depending on what the version required is and how old it is.

[WhyNotHugo]

Rust 1.57.0, from 2021-12-02

[WhyNotHugo]

For tokio, the current MSRV is 1.56.0.

[WhyNotHugo]

I've updated the PR to panic without panic!. I used ([] as [u8; 0])[0];, which is already used as a const panic! hack in a couple of other places in the codebase.

We can remove this hack (both this new instance and existing ones) once the MSRV is bumped to 1.57.0 or greater.

[lperlaki]

I was wondering if we could add a variant StaticRef(&'static [u8]) to the Method Inner enum instead of panicking on longer than 15 byte methods?

[WhyNotHugo]

I don't know of any methods that are longer than 15 bytes, so I'm not sure that it's worth the effort.

[2xsaiko]

What's this stuck on?

[lperlaki]

I would also like to see this being merged as it helps with implementing a webdav server base on hyper

I don't know of any methods that are longer than 15 bytes, so I'm not sure that it's worth the effort.

recently I stubbled over the BASELINE-CONTROL webdav method wich is longe than 15 bytes (16)

I was wondering if we could add a variant StaticRef(&'static [u8]) to the Method Inner enum instead of panicking on longer than 15 byte methods?

figured out that this wouldn't work with the current implementation since the equality also checks the enum variant wich is required that Method can support pattern matching

[orium]

@seanmonstar Anything that needs to be done to land this? Happy to help if there's anything to do.

[WhyNotHugo]

I was wondering if we could add a variant StaticRef(&'static [u8]) to the Method Inner enum instead of panicking on longer than 15 byte methods?

I explored this a bit further.

Adding a new enum variant won't increase the total size of Inner. The associated data is a single reference, so it's also not bigger than the largest of the existing variants.

I've implemented your suggestions. This remove the conditional (compile-time) panic if len > 15.

[WhyNotHugo]

At this point, waiting for feedback from the core devs.

[seanmonstar]

With an ExtensionStatic available, is there a benefit to keeping this one?

[WhyNotHugo]

InlineExtension has no heap allocation and has the data available in the same allocation. Most HTTP methods fit in this case, and it has no overhead.

ExtensionStatic is a niche for unusually long methods, but has a heap allocation and an extra indirection.

We have three options here:

• Keep both. No real downsides aside from another internal type, and does not increase the size of the Method type.
• Keep only InlineExtension, restricting from_static to only methods of len <= 15.
• Keep only ExtensionStatic, forcing any from_static method to use a heap allocation and an extra indirection.

Personally, I prefer the first choice the most, and the third one the least (since it introduces pointless overhead for most WebDAV methods, albeit minor).

[lperlaki]

I found the Problem with ExtensionStatic is that

const BASELINE_CONTROL: Method = Method::from_static(„BASELINE-CONTROL“);

let m = Method::from_bytes(„BASELINE-CONTROL“);

let is_baseline = match m {
    BASELINE_CONTROL => true,
    _ => false,
};

will not match.

[WhyNotHugo]

I found the Problem with ExtensionStatic is that

const BASELINE_CONTROL: Method = Method::from_static(„BASELINE-CONTROL“);

let m = Method::from_bytes(„BASELINE-CONTROL“);

let is_baseline = match m {
    BASELINE_CONTROL => true,
    _ => false,
};

will not match.

I'll add a test for this case and figure out what's wrong.