Alphanumeric enforcement on HeaderName breaks Implementation with Memphis.

[turulix]

As stated above the Alphanumeric enforcement introduced in 0.30.0 breaks custom headers used by memphis.

nats.rs/async-nats/src/header.rs

Lines 502 to 504 in cb0e15a

	if s.contains(|c: char| !c.is_ascii_alphanumeric() && c != '-') {
	return Err(ParseHeaderNameError);
	}

Memphis uses Nats in the background and uses SpecialHeaders like $memphis_producedBy which inclue $, _ and therefor triggering the ParseHeaderNameError

It also appears that the enforcement dosn't happen while inserting into the HeaderMap but rather when reading it at

nats.rs/async-nats/src/connection.rs

Line 295 in cb0e15a

headers.append(HeaderName::from_str(key).unwrap(), value.trim().to_string());

Causing the entire library to panic rather than returning an error.

But I don't understand why the headers are being restricted in the first place, as something like the headers above work absolutly fine, and I didn't find anything in the NATS documentation restricting the use of headers like that. I think if a user wants to use funky HeaderNames just let them do it.

[caspervonb]

But I don't understand why the headers are being restricted in the first place, as something like the headers above work absolutly fine, and I didn't find anything in the NATS documentation restricting the use of headers like that. I think if a user wants to use funky HeaderNames just let them do it.

Header names are specced to be ASCII 33 to 126, excluding colon so that's why.

[turulix]

Ah okay, didn't know. Makes sence. Thank you for this fix! :)

[caspervonb]

Thanks for the catch and report! 💯