Why are spaces rejected in strings listing the filter directives?

[Laifsyn]

Methods like "try_from_env(&str)" which seems to eventually resolve into tracing_subscriber::filter::Builder::parse is rejecting spacings on listed items (aka: not trimming it before parsing). Is there any particular reason for rejecting spacings on listed items?

#[cfg(test)]
mod test {
    use std::str::FromStr;

    use tracing_subscriber::EnvFilter;

    #[test]
    fn test_parsing() {
        let err = EnvFilter::from_str("trace, h2=debug"); // <--- This fails
        assert_eq!("Err(ParseError { kind: Other(None) })", format!("{err:?}"));
        assert_eq!(
            "invalid filter directive",
            err.as_ref().unwrap_err().to_string()
        );
        assert!(err.is_err())
    }
}

[Laifsyn]

I also found this related discussion: #1587, which calls Directive::parse directly, but I guess it doesn't really matter since the user can still just trim the &str it at callsite.

    use tracing_subscriber::{EnvFilter, filter::Directive};

    #[test]
    fn test_parsing_with_directive() {
        let filter = EnvFilter::from("info").add_directive(
            " h3=debug" // Will panic
                .parse::<Directive>()
                .expect("leading/trailling space shouldn't cause it to fail?"),
        );
        assert_eq!("h3=debug,info", filter.to_string());
    }