Function parse_set 

pub fn parse_set(input: &str) -> Result<ParsedSet, String>

Classify one :set argument (without the :set prefix).

Checked in this order, first match wins: contains = → ParsedSet::Assign; ends in ? → ParsedSet::Query; ends in & → ParsedSet::Reset; starts with no → ParsedSet::Negate; otherwise ParsedSet::NameOnly. Err for empty input or an empty name before = / ?.

The no test is purely lexical: any name beginning with no parses as a negation of the remainder, so an option whose own name starts with no cannot be reached by the bare name form.

Examples

use lattice_config::{ParsedSet, parse_set};

assert_eq!(
    parse_set("tabstop = 4"),
    Ok(ParsedSet::Assign { name: "tabstop".into(), value: "4".into() })
);
assert_eq!(parse_set("number?"), Ok(ParsedSet::Query("number".into())));
assert_eq!(parse_set("nowrap"), Ok(ParsedSet::Negate("wrap".into())));
assert_eq!(parse_set("&"), Ok(ParsedSet::Reset(String::new())));
assert!(parse_set("=4").is_err());