A flag to unset all pre-existing variables

[tabokie]

It would make tests more reproducible.

[vmx]

That's a good idea. Though I don't think we need a new flag, this can be done already today with something along the lines of:

let vars_to_unset = std::env::vars().map(|(key, _value)| (key, None)).collect();
temp_env::with_vars(
    [
        vars_to_unset,
        vec![("MY_VAR".to_string(), Some("my_value"))],
    ]
    .concat(),
    || {
        println!("vmx: env without pre-existing vars: {:?}", std::env::vars());
    },
);

Does that solve your problem?

[tabokie]

Calling std::env::vars() directly will again be interfered by other test cases. E.g. test A unsets some variables, test B collects vars_to_unset missing those variables, then test A finishes and test B enters temp_env.

But I agree it'll work if everyone is purely adding additional variables instead of unsetting some.

[vmx]

Calling std::env::vars() directly will again be interfered by other test cases. E.g. test A unsets some variables, test B collects vars_to_unset missing those variables, then test A finishes and test B enters temp_env.

If I understand it correctly, you would set the vars_to_unset once (with a OnceCell` or so) and the other tests would re-use them.

[tabokie]

But that would force every tests to run the setup even if they don't necessarily need a clean environment. Any one test missing the setup && unset some variables in temp_env will cause the problem I described earlier.