Implement unlinkat - Update comments to unlink at and breakup tests

Changes made based on comments from pull request nix-rust#1058

Author: jlb6740

src/unistd.rs

@@ -1154,8 +1154,10 @@ pub enum UnlinkatFlags {
 /// Remove a directory entry
 ///
 /// In the case of a relative path, the directory entry to be removed is determined relative to
-/// the directory associated with the file descriptor dirfd. If flag is UnlinkatFlags::RemoveDir
-/// then remove the directory entry specified by dirfd and path is performed.
+/// the directory associated with the file descriptor `dirfd` or the current working directory
+/// if `dirfd` is `None`. In the case of an absolute `path` `dirfd` is ignored. If `flag` is
+/// `UnlinkatFlags::RemoveDir` then removal of the directory entry specified by `dirfd` and `path`
+/// is performed.
 ///
 /// # References
 /// See also [unlinkat(2)](http://pubs.opengroup.org/onlinepubs/9699919799/functions/unlinkat.html)

test/test_unistd.rs

@@ -602,37 +602,58 @@ fn test_symlinkat() {
 
 
 #[test]
-fn test_unlinkat() {
+#[should_panic]
+fn test_unlinkat_dir_noremovedir() {
     let tempdir = tempfile::tempdir().unwrap();
-    let filename = "foo.txt";
     let dirname = "foo_dir";
-    let filepath = tempdir.path().join(filename);
     let dirpath = tempdir.path().join(dirname);
 
-    // Create file
-    File::create(&filepath).unwrap();
-
     // Create dir
     DirBuilder::new().recursive(true).create(&dirpath).unwrap();
 
     // Get file descriptor for base directory
     let dirfd = fcntl::open(tempdir.path(), fcntl::OFlag::empty(), stat::Mode::empty()).unwrap();
 
     // Attempt unlink dir at relative path without proper flag
-    panic::set_hook(Box::new(|_info| {}));
-    let result = std::panic::catch_unwind(|| unlinkat(Some(dirfd), dirname, UnlinkatFlags::NoRemoveDir).unwrap());
-    assert!(result.is_err());
+    unlinkat(Some(dirfd), dirname, UnlinkatFlags::NoRemoveDir).unwrap();
     assert!(dirpath.exists());
+ }
+
+#[test]
+fn test_unlinkat_dir_removedir() {
+    let tempdir = tempfile::tempdir().unwrap();
+    let dirname = "foo_dir";
+    let dirpath = tempdir.path().join(dirname);
+
+    // Create dir
+    DirBuilder::new().recursive(true).create(&dirpath).unwrap();
+
+    // Get file descriptor for base directory
+    let dirfd = fcntl::open(tempdir.path(), fcntl::OFlag::empty(), stat::Mode::empty()).unwrap();
 
     // Attempt unlink dir at relative path with proper flag
     unlinkat(Some(dirfd), dirname, UnlinkatFlags::RemoveDir).unwrap();
     assert!(!dirpath.exists());
+ }
+
+#[test]
+fn test_unlinkat_file() {
+    let tempdir = tempfile::tempdir().unwrap();
+    let filename = "foo.txt";
+    let filepath = tempdir.path().join(filename);
+
+    // Create file
+    File::create(&filepath).unwrap();
+
+    // Get file descriptor for base directory
+    let dirfd = fcntl::open(tempdir.path(), fcntl::OFlag::empty(), stat::Mode::empty()).unwrap();
 
     // Attempt unlink file at relative path
     unlinkat(Some(dirfd), filename, UnlinkatFlags::NoRemoveDir).unwrap();
     assert!(!filepath.exists());
  }
 
+
 #[test]
 fn test_access_not_existing() {
     let tempdir = tempfile::tempdir().unwrap();