diff --git a/library/std/src/path.rs b/library/std/src/path.rs
index 35e920ab34476..ff4f189f36d45 100644
--- a/library/std/src/path.rs
+++ b/library/std/src/path.rs
@@ -2148,6 +2148,13 @@ pub struct Path {
#[stable(since = "1.7.0", feature = "strip_prefix")]
pub struct StripPrefixError(());
+/// An error returned from [`Path::normalize_lexically`] if a `..` parent reference
+/// would escape the path.
+#[unstable(feature = "normalize_lexically", issue = "134694")]
+#[derive(Debug, PartialEq)]
+#[non_exhaustive]
+pub struct NormalizeError;
+
impl Path {
// The following (private!) function allows construction of a path from a u8
// slice, which is only safe when it is known to follow the OsStr encoding.
@@ -2962,6 +2969,63 @@ impl Path {
fs::canonicalize(self)
}
+ /// Normalize a path, including `..` without traversing the filesystem.
+ ///
+ /// Returns an error if normalization would leave leading `..` components.
+ ///
+ ///
+ ///
+ /// This function always resolves `..` to the "lexical" parent.
+ /// That is "a/b/../c" will always resolve to `a/c` which can change the meaning of the path.
+ /// In particular, `a/c` and `a/b/../c` are distinct on many systems because `b` may be a symbolic link, so its parent isn’t `a`.
+ ///
+ ///
+ ///
+ /// [`path::absolute`](absolute) is an alternative that preserves `..`.
+ /// Or [`Path::canonicalize`] can be used to resolve any `..` by querying the filesystem.
+ #[unstable(feature = "normalize_lexically", issue = "134694")]
+ pub fn normalize_lexically(&self) -> Result {
+ let mut lexical = PathBuf::new();
+ let mut iter = self.components().peekable();
+
+ // Find the root, if any.
+ let root = match iter.peek() {
+ Some(Component::ParentDir) => return Err(NormalizeError),
+ Some(p @ Component::RootDir) | Some(p @ Component::CurDir) => {
+ lexical.push(p);
+ iter.next();
+ lexical.as_os_str().len()
+ }
+ Some(Component::Prefix(prefix)) => {
+ lexical.push(prefix.as_os_str());
+ iter.next();
+ if let Some(p @ Component::RootDir) = iter.peek() {
+ lexical.push(p);
+ iter.next();
+ }
+ lexical.as_os_str().len()
+ }
+ None => return Ok(PathBuf::new()),
+ Some(Component::Normal(_)) => 0,
+ };
+
+ for component in iter {
+ match component {
+ Component::RootDir | Component::Prefix(_) => return Err(NormalizeError),
+ Component::CurDir => continue,
+ Component::ParentDir => {
+ if lexical.as_os_str().len() == root {
+ return Err(NormalizeError);
+ } else {
+ lexical.pop();
+ }
+ }
+ Component::Normal(path) => lexical.push(path),
+ }
+ }
+ Ok(lexical)
+ }
+
/// Reads a symbolic link, returning the file that the link points to.
///
/// This is an alias to [`fs::read_link`].
@@ -3503,6 +3567,15 @@ impl Error for StripPrefixError {
}
}
+#[unstable(feature = "normalize_lexically", issue = "134694")]
+impl fmt::Display for NormalizeError {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ f.write_str("parent reference `..` points outside of base directory")
+ }
+}
+#[unstable(feature = "normalize_lexically", issue = "134694")]
+impl Error for NormalizeError {}
+
/// Makes the path absolute without accessing the filesystem.
///
/// If the path is relative, the current directory is used as the base directory.
diff --git a/library/std/src/path/tests.rs b/library/std/src/path/tests.rs
index ff3f7151bb834..a346d8a43fc62 100644
--- a/library/std/src/path/tests.rs
+++ b/library/std/src/path/tests.rs
@@ -2079,3 +2079,51 @@ fn clone_to_uninit() {
unsafe { a.clone_to_uninit(ptr::from_mut::(&mut b).cast()) };
assert_eq!(a, &*b);
}
+
+#[test]
+fn normalize_lexically() {
+ #[track_caller]
+ fn check(a: &str, b: Result<&str, NormalizeError>) {
+ assert_eq!(Path::new(a).normalize_lexically(), b.map(PathBuf::from));
+ }
+
+ // Relative paths
+ check("a", Ok("a"));
+ check("./a", Ok("./a"));
+ check("a/b/c", Ok("a/b/c"));
+ check("a/././b/./c/.", Ok("a/b/c"));
+ check("a/../c", Ok("c"));
+ check("./a/b", Ok("./a/b"));
+ check("a/../b/c/..", Ok("b"));
+
+ check("..", Err(NormalizeError));
+ check("../..", Err(NormalizeError));
+ check("a/../..", Err(NormalizeError));
+ check("a/../../b", Err(NormalizeError));
+ check("a/../../b/c", Err(NormalizeError));
+ check("a/../b/../..", Err(NormalizeError));
+
+ // Check we don't escape the root or prefix
+ #[cfg(unix)]
+ {
+ check("/..", Err(NormalizeError));
+ check("/a/../..", Err(NormalizeError));
+ }
+ #[cfg(windows)]
+ {
+ check(r"C:\..", Err(NormalizeError));
+ check(r"C:\a\..\..", Err(NormalizeError));
+
+ check(r"C:..", Err(NormalizeError));
+ check(r"C:a\..\..", Err(NormalizeError));
+
+ check(r"\\server\share\..", Err(NormalizeError));
+ check(r"\\server\share\a\..\..", Err(NormalizeError));
+
+ check(r"\..", Err(NormalizeError));
+ check(r"\a\..\..", Err(NormalizeError));
+
+ check(r"\\?\UNC\server\share\..", Err(NormalizeError));
+ check(r"\\?\UNC\server\share\a\..\..", Err(NormalizeError));
+ }
+}