Fixes for Dir on macOS, FreeBSD, and WASI.

Author: sunfishcode

src/backend/libc/fs/dir.rs

@@ -46,6 +46,7 @@ impl Dir {
     }
 
     #[inline]
+    #[allow(unused_mut)]
     fn _read_from(fd: BorrowedFd<'_>) -> io::Result<Self> {
         let mut any_errors = false;
 
@@ -57,6 +58,7 @@ impl Dir {
         let flags = fcntl_getfl(fd)?;
         let fd_for_dir = match openat(fd, cstr!("."), flags | OFlags::CLOEXEC, Mode::empty()) {
             Ok(fd) => fd,
+            #[cfg(not(target_os = "wasi"))]
             Err(io::Errno::NOENT) => {
                 // If "." doesn't exist, it means the directory was removed.
                 // We treat that as iterating through a directory with no
@@ -341,6 +343,13 @@ fn dir_iterator_handles_io_errors() {
         core::mem::forget(owned_fd);
     }
 
+    // FreeBSD and macOS seem to read some directory entries before we call
+    // `.next()`.
+    #[cfg(any(apple, freebsdlike))]
+    {
+        dir.rewind();
+    }
+
     assert!(matches!(dir.next(), Some(Err(_))));
     assert!(matches!(dir.next(), None));
 }

tests/fs/dir.rs

@@ -62,6 +62,10 @@ fn test_dir() {
     assert!(saw_cargo_toml);
 }
 
+// Test that `Dir` silently stops iterating if the directory has been removed.
+//
+// Except on FreeBSD and macOS, where apparently `readdir` just keeps reading.
+#[cfg_attr(any(apple, freebsdlike), ignore)]
 #[test]
 fn dir_iterator_handles_dir_removal() {
     // create a dir, keep the FD, then delete the dir
@@ -83,6 +87,7 @@ fn dir_iterator_handles_dir_removal() {
 
 // Like `dir_iterator_handles_dir_removal`, but close the directory after
 // `Dir::read_from`.
+#[cfg_attr(any(apple, freebsdlike), ignore)]
 #[test]
 fn dir_iterator_handles_dir_removal_after_open() {
     // create a dir, keep the FD, then delete the dir