rreverser / cow-utils-rs Goto Github PK

We often have to trim strings because some values contain superfluous whitespace while most values do not. To avoid reallocating a new string for the majority of the values, we currently use a little extension trait called TrimExt with works like

impl TrimExt for String {
    fn trim(self) -> Self {
        let val = self.as_str().trim();

        if val.len() != self.len() {
            val.to_owned()
        } else {
            self
        }
    }
}

i.e. it keeps to original value if the trimming is actually a no-op.

So this does not really fit into the CowUtils trait as far I can see, but I think one could say that it does fit with this crate's aim of avoiding allocations when no modifications are necessary.

Would you be interested in adding a new trait to capture this problem which I think is sort of a converse to the replace problem, i.e. we start with an owned value and want to keep it if possible.

use cow_utils::*;

fn main() {
    let s = "ᾈ";
    assert_eq!(s.to_lowercase(), s.cow_to_lowercase())
}

$ cargo run                 
    Finished dev [unoptimized + debuginfo] target(s) in 0.00s
     Running `target/debug/cwl`
thread 'main' panicked at 'assertion failed: `(left == right)`
  left: `"ᾀ"`,
 right: `"ᾈ"`', src/main.rs:5:5

We ran across this doing some proptesting against some of our code that uses cow_to_lowercase(). ᾈ has no particular meaning to us -- it's just the reduced value that proptest found.

I see this crate hasn't been updated in about 4 years, but I thought this was useful to report. We really like cow-utils, so even if this is deemed unworthy of fixing, thanks for a great piece of software.