Exclude setting "async-std" and "tokio" features at the same time.

[luukvanderduim]

In atspi/src/lib.rs
https://github.com/odilia-app/atspi/blob/c3338f4373ca5c0240e7dc9d3fddf832e102ecaf/atspi/src/lib.rs#L10C1-L11C89

#[cfg(all(not(feature = "async-std"), not(feature = "tokio")))]
compile_error!("You must specify at least one of the `async-std` or `tokio` features.");

This warns us when neither "async-std" or "tokio" is set.

What about having both set?
This could easily happen I were to

[dependencies]
atspi = { version = "0.22", features = ["connection-tokio"] } 

I believe this leads to having the default feature "async-std" set as well as "tokio". Right?
Is there a way to unset one if the other is set automatically and vice versa?

[TTWNO]

Yes... I think you're right about that.

No, I don't think you can disable a festure when another is enabled.

[TTWNO]

I think this was changed when async-std and tokio were both allowed as features of zbus. And I said "oh good! now I don't have to worry about atspi having both either!"

But I think you're right to be concrrned here.

[luukvanderduim]

I have consulted the zbus sources:
This seems to affect error_message only - I think?

#[cfg(all(not(feature = "async-io"), not(feature = "tokio")))]
mod error_message {
    #[cfg(windows)]
    compile_error!("Either \"async-io\" (default) or \"tokio\" must be enabled. On Windows \"async-io\" is (currently) required for UNIX socket support");

    #[cfg(not(windows))]
    compile_error!("Either \"async-io\" (default) or \"tokio\" must be enabled.");
}

I did find instances like:

    /// Runs a single task.
    ///
    /// With `tokio` feature enabled, its a noop and never returns.
    pub async fn tick(&self) {
        #[cfg(not(feature = "tokio"))]
        {
            self.executor.tick().await
        }

        #[cfg(feature = "tokio")]
        {
            pending().await
        }
    }

At first glance I'd say it is unreasonable to allow both enabled.
I will try to enable both in a test program and break something and make lots of drama elsewhere ;')