Add Dir::create_new, analogous to File::create_new

cap-std/src/fs/dir.rs

@@ -202,6 +202,18 @@ impl Dir {
         )
     }
 
+    /// Creates a new file in read-write mode; error if the file already exists.
+    ///
+    /// This corresponds to [`std::fs::File::create_new`], but only accesses paths relative to
+    /// `self`.
+    #[inline]
+    pub fn create_new<P: AsRef<Path>>(&self, path: P) -> io::Result<File> {
+        self.open_with(
+            path,
+            OpenOptions::new().read(true).write(true).create_new(true),
+        )
+    }
+
     /// Returns the canonical form of a path with all intermediate components
     /// normalized and symbolic links resolved.
     ///

cap-std/src/fs_utf8/dir.rs

@@ -143,6 +143,16 @@ impl Dir {
         self.cap_std.create(path).map(File::from_cap_std)
     }
 
+    /// Creates a new file in read-write mode; error if the file already exists.
+    ///
+    /// This corresponds to [`std::fs::File::create_new`], but only accesses paths relative to
+    /// `self`.
+    #[inline]
+    pub fn create_new<P: AsRef<Utf8Path>>(&self, path: P) -> io::Result<File> {
+        let path = from_utf8(path.as_ref())?;
+        self.cap_std.create_new(path).map(File::from_cap_std)
+    }
+
     /// Returns the canonical form of a path with all intermediate components
     /// normalized and symbolic links resolved.
     ///

tests/fs.rs

@@ -519,7 +519,7 @@ fn file_test_directoryinfo_readdir() {
 }
 
 #[test]
-fn file_create_new_already_exists_error() {
+fn file_create_new_via_openoptions_already_exists_error() {
     let tmpdir = tmpdir();
     let file = "file_create_new_error_exists";
     check!(tmpdir.create(file));
@@ -529,6 +529,15 @@ fn file_create_new_already_exists_error() {
     assert_eq!(e.kind(), ErrorKind::AlreadyExists);
 }
 
+#[test]
+fn file_create_new_already_exists_error() {
+    let tmpdir = tmpdir();
+    let file = "file_create_new_error_exists";
+    check!(tmpdir.create(file));
+    let e = tmpdir.create_new(file).unwrap_err();
+    assert_eq!(e.kind(), ErrorKind::AlreadyExists);
+}
+
 #[test]
 fn mkdir_path_already_exists_error() {
     let tmpdir = tmpdir();