Map EACCES -> EPERM for hard links to directories

crates/test-programs/wasi-tests/src/bin/path_link.rs

@@ -136,13 +136,12 @@ unsafe fn test_path_link(dir_fd: wasi::Fd) {
     wasi::path_create_directory(dir_fd, "subdir").expect("creating a subdirectory");
     create_or_open(dir_fd, "subdir", wasi::OFLAGS_DIRECTORY);
 
-    let err = wasi::path_link(dir_fd, 0, "subdir", dir_fd, "link")
-        .expect_err("creating a link to a directory should fail")
-        .raw_error();
-    assert!(
-        err == wasi::ERRNO_PERM || err == wasi::ERRNO_ACCES,
-        "errno should be ERRNO_PERM or ERRNO_ACCESS, was: {}",
-        err
+    assert_eq!(
+        wasi::path_link(dir_fd, 0, "subdir", dir_fd, "link")
+            .expect_err("creating a link to a directory should fail")
+            .raw_error(),
+        wasi::ERRNO_PERM,
+        "errno should be ERRNO_PERM"
     );
     wasi::path_remove_directory(dir_fd, "subdir").expect("removing a subdirectory");
 

crates/wasi-common/src/sys/windows/path.rs

@@ -189,11 +189,12 @@ pub(crate) fn link(
             Some(code) => {
                 debug!("path_link at fs::hard_link error code={:?}", code);
                 match code as u32 {
-                    // TODO is this needed at all????
                     winerror::ERROR_ACCESS_DENIED => {
-                        // does the target exist?
-                        if new_path.exists() {
-                            return Err(Errno::Exist);
+                        // If an attempt is made to create a hard link to a directory, POSIX-compliant
+                        // implementations of link return `EPERM`, but `ERROR_ACCESS_DENIED` is converted
+                        // to `EACCES`. We detect and correct this case here.
+                        if fs::metadata(new_path).map(|m| m.is_dir()).unwrap_or(false) {
+                            return Err(Errno::Perm);
                         }
                     }
                     _ => {}