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use std::env;
use std::ffi::{OsStr, OsString};
pub struct ScopedEnv<T>
where
T: AsRef<OsStr>,
{
name: T,
old_value: Option<OsString>,
}
impl<T> ScopedEnv<T>
where
T: AsRef<OsStr>,
{
pub fn set(name: T, value: T) -> Self {
let old_value = env::var_os(name.as_ref());
env::set_var(name.as_ref(), value);
Self { name, old_value }
}
pub fn remove(name: T) -> Self {
let old_value = env::var_os(name.as_ref());
env::remove_var(name.as_ref());
Self { name, old_value }
}
}
impl<T> AsRef<OsStr> for ScopedEnv<T>
where
T: AsRef<OsStr>,
{
fn as_ref(&self) -> &OsStr {
self.name.as_ref()
}
}
impl<T> Drop for ScopedEnv<T>
where
T: AsRef<OsStr>,
{
fn drop(&mut self) {
match self.old_value {
Some(ref old_value) => env::set_var(self.as_ref(), old_value),
None => env::remove_var(self),
}
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn does_set() {
let c = ScopedEnv::set("FOOBAR", "hello");
assert_eq!(env::var(c).unwrap(), "hello");
}
#[test]
fn does_unset_at_end_of_block() {
env::remove_var("FOOBAR1");
{
let c = ScopedEnv::set("FOOBAR1", "hello");
assert_eq!(env::var(c).unwrap(), "hello");
}
assert_eq!(env::var_os("FOOBAR1"), None);
}
#[test]
fn does_reset_at_end_of_block() {
env::set_var("FOOBAR1", "OLD_VALUE");
{
let c = ScopedEnv::set("FOOBAR1", "hello");
assert_eq!(env::var(c).unwrap(), "hello");
}
assert_eq!(env::var("FOOBAR1").unwrap(), "OLD_VALUE");
}
#[test]
fn does_remove() {
env::set_var("FOOBAR", "SOME_VALUE");
{
let c = ScopedEnv::remove("FOOBAR");
assert_eq!(env::var_os(c), None);
}
assert_eq!(env::var_os("FOOBAR").unwrap(), "SOME_VALUE");
}
}