Fix path_rename on *nix hosts

The fix contains an errno remapping in macOS case where in case
when we try to rename a file into a path with a trailing slash an
ENOENT is returned. In this case, if the destination does not exist,
an ENOTDIR should be thrown as is thrown correctly on Linux hosts.
Thus, as a fix, if an ENOENT is thrown, an additional check is
performed to see whether the destination path indeed contains
a trailing slash, and if so, the errno is adjusted to ENOTDIR
to match the POSIX/WASI spec.

src/hostcalls_impl/fs.rs

@@ -707,8 +707,11 @@ pub(crate) unsafe fn path_rename(
     let new_dirfd = wasi_ctx
         .get_fd_entry(new_dirfd, host::__WASI_RIGHT_PATH_RENAME_TARGET, 0)
         .and_then(|fe| fe.fd_object.descriptor.as_file())?;
-    let resolved_old = path_get(old_dirfd, 0, old_path, false)?;
-    let resolved_new = path_get(new_dirfd, 0, new_path, false)?;
+    let resolved_old = path_get(old_dirfd, 0, old_path, true)?;
+    let resolved_new = path_get(new_dirfd, 0, new_path, true)?;
+
+    log::debug!("path_rename resolved_old={:?}", resolved_old);
+    log::debug!("path_rename resolved_new={:?}", resolved_new);
 
     hostcalls_impl::path_rename(resolved_old, resolved_new)
 }

src/sys/unix/bsd/hostcalls_impl.rs

@@ -1,11 +1,61 @@
 use super::osfile::OsFile;
+use crate::hostcalls_impl::PathGet;
 use crate::sys::host_impl;
 use crate::{host, Error, Result};
 use nix::libc::{self, c_long, c_void};
 use std::convert::TryInto;
+use std::ffi::CString;
 use std::fs::File;
 use std::os::unix::prelude::AsRawFd;
 
+pub(crate) fn path_rename(resolved_old: PathGet, resolved_new: PathGet) -> Result<()> {
+    use nix::{errno::Errno, fcntl::AtFlags, libc::renameat, sys::stat::fstatat};
+    let old_path_cstr = CString::new(resolved_old.path().as_bytes()).map_err(|_| Error::EILSEQ)?;
+    let new_path_cstr = CString::new(resolved_new.path().as_bytes()).map_err(|_| Error::EILSEQ)?;
+
+    let res = unsafe {
+        renameat(
+            resolved_old.dirfd().as_raw_fd(),
+            old_path_cstr.as_ptr(),
+            resolved_new.dirfd().as_raw_fd(),
+            new_path_cstr.as_ptr(),
+        )
+    };
+    if res != 0 {
+        // Currently, this is verified to be correct on macOS, where
+        // ENOENT can be returned in case when we try to rename a file
+        // into a name with a trailing slash. On macOS, if the latter does
+        // not exist, an ENOENT is thrown, whereas on Linux we observe the
+        // correct behaviour of throwing an ENOTDIR since the destination is
+        // indeed not a directory.
+        //
+        // TODO
+        // Verify on other BSD-based OSes.
+        match Errno::last() {
+            Errno::ENOENT => {
+                // check if the source path exists
+                if let Ok(_) = fstatat(
+                    resolved_old.dirfd().as_raw_fd(),
+                    resolved_old.path(),
+                    AtFlags::AT_SYMLINK_NOFOLLOW,
+                ) {
+                    // check if destination contains a trailing slash
+                    if resolved_new.path().contains('/') {
+                        Err(Error::ENOTDIR)
+                    } else {
+                        Err(Error::ENOENT)
+                    }
+                } else {
+                    Err(Error::ENOENT)
+                }
+            }
+            x => Err(host_impl::errno_from_nix(x)),
+        }
+    } else {
+        Ok(())
+    }
+}
+
 pub(crate) fn fd_readdir(
     os_file: &mut OsFile,
     host_buf: &mut [u8],

src/sys/unix/hostcalls_impl/fs.rs

@@ -207,26 +207,6 @@ pub(crate) fn path_readlink(resolved: PathGet, buf: &mut [u8]) -> Result<usize>
     }
 }
 
-pub(crate) fn path_rename(resolved_old: PathGet, resolved_new: PathGet) -> Result<()> {
-    use nix::libc::renameat;
-    let old_path_cstr = CString::new(resolved_old.path().as_bytes()).map_err(|_| Error::EILSEQ)?;
-    let new_path_cstr = CString::new(resolved_new.path().as_bytes()).map_err(|_| Error::EILSEQ)?;
-
-    let res = unsafe {
-        renameat(
-            resolved_old.dirfd().as_raw_fd(),
-            old_path_cstr.as_ptr(),
-            resolved_new.dirfd().as_raw_fd(),
-            new_path_cstr.as_ptr(),
-        )
-    };
-    if res != 0 {
-        Err(host_impl::errno_from_nix(nix::errno::Errno::last()))
-    } else {
-        Ok(())
-    }
-}
-
 pub(crate) fn fd_filestat_get_impl(file: &std::fs::File) -> Result<host::__wasi_filestat_t> {
     use std::os::unix::fs::MetadataExt;
 

src/sys/unix/linux/hostcalls_impl.rs

@@ -1,11 +1,33 @@
 use super::osfile::OsFile;
+use crate::hostcalls_impl::PathGet;
 use crate::sys::host_impl;
 use crate::{host, Error, Result};
 use nix::libc::{self, c_long, c_void};
 use std::convert::TryInto;
+use std::ffi::CString;
 use std::fs::File;
 use std::os::unix::prelude::AsRawFd;
 
+pub(crate) fn path_rename(resolved_old: PathGet, resolved_new: PathGet) -> Result<()> {
+    use nix::libc::renameat;
+    let old_path_cstr = CString::new(resolved_old.path().as_bytes()).map_err(|_| Error::EILSEQ)?;
+    let new_path_cstr = CString::new(resolved_new.path().as_bytes()).map_err(|_| Error::EILSEQ)?;
+
+    let res = unsafe {
+        renameat(
+            resolved_old.dirfd().as_raw_fd(),
+            old_path_cstr.as_ptr(),
+            resolved_new.dirfd().as_raw_fd(),
+            new_path_cstr.as_ptr(),
+        )
+    };
+    if res != 0 {
+        Err(host_impl::errno_from_nix(nix::errno::Errno::last()))
+    } else {
+        Ok(())
+    }
+}
+
 pub(crate) fn fd_readdir(
     os_file: &mut OsFile,
     host_buf: &mut [u8],