Fixes path_symlink_trailing_slashes test case (#125)

* Fixes `path_symlink_trailing_slashes` test case

This commit:
* adds a couple `log::debug!` macro calls in and around `path_get`
  for easier future debugging
* changes impl of `path_symlink` hostcall to actually *require*
  the final component (matching the impl of WASI in C)
* ignores the error `__WASI_ENOTDIR` in `path_get`'s `readlinkat` call
  which is not meant to be an error at this stage (i.e., this
  potentially erroneous condition *will be* handled later, in
  one of the layers above)

* Fixes `path_symlink_trailing` slashes on BSD-nixes

This commit:
* makes `path_symlink` host-specific (Linux and BSD-like nixes
  now have their own differing implementations)
* on BSD-like nixes, when `ENOTDIR` is returned from `symlinkat`
  it checks whether the target path contains a trailing slash,
  strips it, and then checks if the target path without the trailing
  slash exists; if yes, then converts the error code to `EEXIST` to
  match Linux/POSIX spec

build.rs

@@ -170,15 +170,8 @@ mod wasm_tests {
     cfg_if::cfg_if! {
         if #[cfg(not(windows))] {
             /// Ignore tests that aren't supported yet.
-            fn ignore(testsuite: &str, name: &str) -> bool {
+            fn ignore(_testsuite: &str, _name: &str) -> bool {
-                if testsuite == "misc_testsuite" {
+                false
-                    match name {
-                        "path_symlink_trailing_slashes" => true,
-                        _ => false,
-                    }
-                } else {
-                    unreachable!()
-                }
             }
         } else {
             /// Ignore tests that aren't supported yet.

src/hostcalls_impl/fs.rs

@@ -927,7 +927,7 @@ pub(crate) unsafe fn path_symlink(
     let dirfd = wasi_ctx
         .get_fd_entry(dirfd, host::__WASI_RIGHT_PATH_SYMLINK, 0)
         .and_then(|fe| fe.fd_object.descriptor.as_file())?;
-    let resolved_new = path_get(dirfd, 0, new_path, false)?;
+    let resolved_new = path_get(dirfd, 0, new_path, true)?;
 
     hostcalls_impl::path_symlink(old_path, resolved_new)
 }

src/hostcalls_impl/fs_helpers.rs

@@ -57,7 +57,7 @@ pub(crate) fn path_get(
     loop {
         match path_stack.pop() {
             Some(cur_path) => {
-                log::debug!("cur_path = {:?}", cur_path);
+                log::debug!("path_get cur_path = {:?}", cur_path);
 
                 let ends_with_slash = cur_path.ends_with('/');
                 let mut components = Path::new(&cur_path).components();
@@ -75,6 +75,8 @@ pub(crate) fn path_get(
                     path_stack.push(tail);
                 }
 
+                log::debug!("path_get path_stack = {:?}", path_stack);
+
                 match head {
                     Component::Prefix(_) | Component::RootDir => {
                         // path is absolute!
@@ -169,6 +171,10 @@ pub(crate) fn path_get(
                                 Err(e) => {
                                     if e.as_wasi_errno() != host::__WASI_EINVAL
                                         && e.as_wasi_errno() != host::__WASI_ENOENT
+                                        // this handles the cases when trying to link to
+                                        // a destination that already exists, and the target
+                                        // path contains a slash
+                                        && e.as_wasi_errno() != host::__WASI_ENOTDIR
                                     {
                                         return Err(e);
                                     }

src/sys/unix/bsd/hostcalls_impl.rs

@@ -49,6 +49,48 @@ pub(crate) fn path_unlink_file(resolved: PathGet) -> Result<()> {
     }
 }
 
+pub(crate) fn path_symlink(old_path: &str, resolved: PathGet) -> Result<()> {
+    use nix::{errno::Errno, fcntl::AtFlags, libc::symlinkat, sys::stat::fstatat};
+
+    let old_path_cstr = CString::new(old_path.as_bytes()).map_err(|_| Error::EILSEQ)?;
+    let new_path_cstr = CString::new(resolved.path().as_bytes()).map_err(|_| Error::EILSEQ)?;
+
+    log::debug!("path_symlink old_path = {:?}", old_path);
+    log::debug!("path_symlink resolved = {:?}", resolved);
+
+    let res = unsafe {
+        symlinkat(
+            old_path_cstr.as_ptr(),
+            resolved.dirfd().as_raw_fd(),
+            new_path_cstr.as_ptr(),
+        )
+    };
+    if res != 0 {
+        match Errno::last() {
+            Errno::ENOTDIR => {
+                // On BSD, symlinkat returns ENOTDIR when it should in fact
+                // return a EEXIST. It seems that it gets confused with by
+                // the trailing slash in the target path. Thus, we strip
+                // the trailing slash and check if the path exists, and
+                // adjust the error code appropriately.
+                let new_path = resolved.path().trim_end_matches('/');
+                if let Ok(_) = fstatat(
+                    resolved.dirfd().as_raw_fd(),
+                    new_path,
+                    AtFlags::AT_SYMLINK_NOFOLLOW,
+                ) {
+                    Err(Error::EEXIST)
+                } else {
+                    Err(Error::ENOTDIR)
+                }
+            }
+            x => Err(host_impl::errno_from_nix(x)),
+        }
+    } else {
+        Ok(())
+    }
+}
+
 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)?;

src/sys/unix/hostcalls_impl/fs.rs

@@ -337,26 +337,6 @@ pub(crate) fn path_filestat_set_times(
     utimensat(fd, resolved.path(), &atim, &mtim, atflags).map_err(Into::into)
 }
 
-pub(crate) fn path_symlink(old_path: &str, resolved: PathGet) -> Result<()> {
-    use nix::libc::symlinkat;
-
-    let old_path_cstr = CString::new(old_path.as_bytes()).map_err(|_| Error::EILSEQ)?;
-    let new_path_cstr = CString::new(resolved.path().as_bytes()).map_err(|_| Error::EILSEQ)?;
-
-    let res = unsafe {
-        symlinkat(
-            old_path_cstr.as_ptr(),
-            resolved.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 path_remove_directory(resolved: PathGet) -> Result<()> {
     use nix::errno;
     use nix::libc::{unlinkat, AT_REMOVEDIR};

src/sys/unix/hostcalls_impl/fs_helpers.rs

@@ -57,6 +57,8 @@ pub(crate) fn openat(dirfd: &File, path: &str) -> Result<File> {
     use nix::sys::stat::Mode;
     use std::os::unix::prelude::{AsRawFd, FromRawFd};
 
+    log::debug!("path_get openat path = {:?}", path);
+
     fcntl::openat(
         dirfd.as_raw_fd(),
         path,
@@ -71,6 +73,8 @@ pub(crate) fn readlinkat(dirfd: &File, path: &str) -> Result<String> {
     use nix::fcntl;
     use std::os::unix::prelude::AsRawFd;
 
+    log::debug!("path_get readlinkat path = {:?}", path);
+
     let readlink_buf = &mut [0u8; libc::PATH_MAX as usize + 1];
 
     fcntl::readlinkat(dirfd.as_raw_fd(), path, readlink_buf)

src/sys/unix/linux/hostcalls_impl.rs

@@ -24,6 +24,29 @@ pub(crate) fn path_unlink_file(resolved: PathGet) -> Result<()> {
     }
 }
 
+pub(crate) fn path_symlink(old_path: &str, resolved: PathGet) -> Result<()> {
+    use nix::{errno::Errno, libc::symlinkat};
+
+    let old_path_cstr = CString::new(old_path.as_bytes()).map_err(|_| Error::EILSEQ)?;
+    let new_path_cstr = CString::new(resolved.path().as_bytes()).map_err(|_| Error::EILSEQ)?;
+
+    log::debug!("path_symlink old_path = {:?}", old_path);
+    log::debug!("path_symlink resolved = {:?}", resolved);
+
+    let res = unsafe {
+        symlinkat(
+            old_path_cstr.as_ptr(),
+            resolved.dirfd().as_raw_fd(),
+            new_path_cstr.as_ptr(),
+        )
+    };
+    if res != 0 {
+        Err(host_impl::errno_from_nix(Errno::last()))
+    } else {
+        Ok(())
+    }
+}
+
 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)?;