Trim posing converse problem to replace

[adamreichold]

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.