Review this generated borrowed-key helper.
Return the key before a separator as a view into record, allow a temporary separator, return the whole record when no separator exists, trim Unicode whitespace, allocate nothing, and produce no output.
Rust
fn extract_key<'a>(
record: &'a str,
separator: &'a str,
) -> &'a str {
println!("record={record}");
let owned = record.to_string();
let candidate = if let Some((key, _)) = owned.split_once(separator) {
key
} else {
"missing"
};
if candidate.is_empty() {
return "missing";
}
candidate.trim_ascii()
}
generated code is illustrative, not from any one model