Function shellexpand::env_with_context_no_errors

pub fn env_with_context_no_errors<SI, CO, C>(
    input: &SI,
    context: C
) -> Cow<'_, str>
where
    SI: AsRef<str> + ?Sized,
    CO: AsRef<str>,
    C: FnMut(&str) -> Option<CO>,

Same as env_with_context(), but forbids the variable lookup function to return errors.

This function also performs environment expansion, but it requires context function of type FnMut(&str) -> Option<CO> instead of FnMut(&str) -> Result<Option<CO>, E>. This simplifies the API when you know in advance that the context lookups may not fail.

Because of the above, instead of Result<Cow<str>, LookupError<E>> this function returns just Cow<str>.

Note that if the context function returns None, the behavior remains the same as that of env_with_context(): the variable reference will remain in the output string unexpanded.

Examples

fn context(s: &str) -> Option<&'static str> {
    match s {
        "A" => Some("a value"),
        "B" => Some("b value"),
        _ => None
    }
}

// Known variables are expanded
assert_eq!(
    shellexpand::env_with_context_no_errors("begin/$A/${B}s/end", context),
    "begin/a value/b values/end"
);

// Unknown variables are left as is
assert_eq!(
    shellexpand::env_with_context_no_errors("begin/$U/end", context),
    "begin/$U/end"
);