tests: fix env guard and pipe read for tab dnd

src/process.rs

@@ -9,18 +9,28 @@ use std::process::{Command, Stdio, exit};
 #[cfg(feature = "tokio")]
 use tokio::io::AsyncReadExt;
 
-#[cfg(feature = "tokio")]
 async fn read_from_pipe(read: OwnedFd) -> Option<u32> {
-    let mut read = tokio::net::unix::pipe::Receiver::from_owned_fd(read).unwrap();
-    read.read_u32().await.ok()
-}
+    #[cfg(feature = "tokio")]
+    {
+        let mut read = tokio::net::unix::pipe::Receiver::from_owned_fd(read).unwrap();
+        return read.read_u32().await.ok();
+    }
 
-#[cfg(all(feature = "smol", not(feature = "tokio")))]
-async fn read_from_pipe(read: OwnedFd) -> Option<u32> {
-    let mut read = smol::Async::new(std::fs::File::from(read)).unwrap();
-    let mut bytes = [0; 4];
-    read.read_exact(&mut bytes).await.ok()?;
-    Some(u32::from_be_bytes(bytes))
+    #[cfg(all(feature = "smol", not(feature = "tokio")))]
+    {
+        let mut read = smol::Async::new(std::fs::File::from(read)).unwrap();
+        let mut bytes = [0; 4];
+        read.read_exact(&mut bytes).await.ok()?;
+        return Some(u32::from_be_bytes(bytes));
+    }
+
+    #[cfg(not(any(feature = "tokio", feature = "smol")))]
+    {
+        use rustix::fd::AsFd;
+        let mut bytes = [0u8; 4];
+        rustix::io::read(&read, &mut bytes).ok()?;
+        return Some(u32::from_be_bytes(bytes));
+    }
 }
 
 /// Performs a double fork with setsid to spawn and detach a command.