Make all source files visible to rustfmt

[dtolnay]

The pervasive reliance on cfg_if!, which is not understandable by rustfmt, was leading to only 18/81 source files in this crate able to be covered by cargo fmt. This PR works around that and formats the other 63 files.

[GuillaumeGomez]

So just to confirm: this cfg is always evaluated to false but at least it allows rustfmt to see the file. That's a super clever trick. Thanks for that!

[dtolnay]

That's right.

In the longer term, hopefully rustfmt will get a built-in understanding of the syntax of cfg_if! (rust-lang/rustfmt#3253) or cfg_match! (rust-lang/rust#115585) and the workaround won't be needed.

Or alternatively, someone might make an alternative macro that doesn't rely on dedicated rustfmt support for its syntax, something like:

#[apply_cfg]
enum __ {
    r#if = #[cfg(feature = "unknown-ci")]
    {
        // This is used in CI to check that the build for unknown targets is compiling fine.
        mod unknown;
        use crate::unknown as sys;

        #[cfg(test)]
        pub(crate) const MIN_USERS: usize = 0;
    },

    r#else = #[cfg(any(
        target_os = "macos",
        target_os = "ios",
        target_os = "linux",
        target_os = "android",
        target_os = "freebsd"
    ))]
    {
        mod unix;
        use crate::unix::sys;

        #[cfg(feature = "network")]
        mod network;
        #[cfg(feature = "network")]
        use crate::unix::network_helper;

        #[cfg(test)]
        pub(crate) const MIN_USERS: usize = 1;
    },

    ...
}

[GuillaumeGomez]

I prefer the current solution. It duplicates code but at least it's "easy" to see what's going on. Gonna check with rustfmt team if they'd be open to add some special cases for macros like cfg_if!.

[GuillaumeGomez]

Makes me a bit sad to have all these manual imports but the code formatting is finally working, thanks a lot! Gonna open an issue on rustfmt to see if they can work with cfg_if!.