Add WalkConfiguration::skip_mountpoints()

src/dirext.rs

@@ -59,6 +59,9 @@ pub struct WalkConfiguration<'p> {
     /// Do not cross devices.
     noxdev: bool,
 
+    /// Skip mount points entirely (do not visit or traverse them).
+    skip_mountpoints: bool,
+
     path_base: Option<&'p Path>,
 
     // It's not *that* complex of a type, come on clippy...
@@ -73,18 +76,39 @@ impl std::fmt::Debug for WalkConfiguration<'_> {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         f.debug_struct("WalkConfiguration")
             .field("noxdev", &self.noxdev)
+            .field("skip_mountpoints", &self.skip_mountpoints)
             .field("sorter", &self.sorter.as_ref().map(|_| true))
             .finish()
     }
 }
 
 impl<'p> WalkConfiguration<'p> {
-    /// Enable configuration to not traverse mount points
+    /// Enable configuration to not traverse mount points.
+    ///
+    /// Note that the mount point directory itself will still be visited
+    /// (passed to the callback); only traversal into it is prevented.
+    /// To skip mount point directories entirely, use [`skip_mountpoints`](Self::skip_mountpoints).
     pub fn noxdev(mut self) -> Self {
         self.noxdev = true;
         self
     }
 
+    /// Skip mount point directories entirely during the walk.
+    ///
+    /// When enabled, directories that are mount points will not be visited
+    /// (the callback will not be invoked for them) and will not be traversed.
+    ///
+    /// This is independent from [`noxdev`](Self::noxdev) -- `skip_mountpoints`
+    /// controls whether mount point directories are visited at all, while
+    /// `noxdev` controls whether the walk traverses into directories on
+    /// different devices. In practice you may want to use both together.
+    ///
+    /// This option currently only has an effect on Linux.
+    pub fn skip_mountpoints(mut self) -> Self {
+        self.skip_mountpoints = true;
+        self
+    }
+
     /// Set a function for sorting directory entries.
     pub fn sort_by<F>(mut self, cmp: F) -> Self
     where
@@ -556,6 +580,14 @@ where
         let ty = entry.file_type()?;
         let is_dir = ty.is_dir();
         let name = entry.file_name();
+        // If skip_mountpoints is enabled and this is a directory,
+        // check if it's a mount point and skip it entirely.
+        #[cfg(any(target_os = "android", target_os = "linux"))]
+        if is_dir && config.skip_mountpoints {
+            if let Some(true) = is_mountpoint_impl_statx(d, Path::new(&name))? {
+                continue;
+            }
+        }
         // The path provided to the user includes the current filename
         path.push(&name);
         let filename = &name;

tests/it/main.rs

@@ -722,6 +722,59 @@ fn test_walk_noxdev() -> Result<()> {
     Ok(())
 }
 
+#[test]
+#[cfg(any(target_os = "android", target_os = "linux"))]
+fn test_walk_skip_mountpoints() -> Result<()> {
+    let rootfs = Dir::open_ambient_dir("/", cap_std::ambient_authority())?;
+
+    // Count root entries that are mountpoints
+    let n_root_entries = std::fs::read_dir("/")?.count();
+    let mut n_mountpoints = 0;
+    for entry in std::fs::read_dir("/")? {
+        let entry = entry?;
+        if entry.file_type()?.is_dir() {
+            if let Some(true) = rootfs.is_mountpoint(entry.file_name())? {
+                n_mountpoints += 1;
+            }
+        }
+    }
+    assert!(
+        n_mountpoints > 0,
+        "expected at least one mountpoint under /"
+    );
+
+    // Walk with skip_mountpoints; don't traverse into any directories.
+    let mut visited = 0;
+    rootfs
+        .walk(
+            &WalkConfiguration::default().skip_mountpoints(),
+            |e| -> std::io::Result<_> {
+                // Verify this entry is not a mountpoint
+                if e.file_type.is_dir() {
+                    let is_mp = e.dir.is_mountpoint(e.filename)?;
+                    assert_ne!(
+                        is_mp,
+                        Some(true),
+                        "mountpoint {:?} should have been skipped",
+                        e.path
+                    );
+                }
+                visited += 1;
+                // Don't traverse into subdirectories, but continue iterating siblings
+                if e.file_type.is_dir() {
+                    Ok(ControlFlow::Break(()))
+                } else {
+                    Ok(ControlFlow::Continue(()))
+                }
+            },
+        )
+        .unwrap();
+    // We should see all root entries minus the mountpoints
+    assert_eq!(visited, n_root_entries - n_mountpoints);
+
+    Ok(())
+}
+
 #[test]
 #[cfg(any(target_os = "android", target_os = "linux"))]
 fn test_xattrs() -> Result<()> {