fix: retrieve metadata for symbolic links without following them

Previously, the function get_metadata in platform.rs used `fs::metadata` which follows symbolic links
and returns metadata for the target file. This caused issues #421: du / dust disagreement
when trying to determine properties of the symbolic link itself

src/dir_walker.rs

@@ -115,9 +115,11 @@ fn sort_by_inode(a: &Node, b: &Node) -> std::cmp::Ordering {
 fn ignore_file(entry: &DirEntry, walk_data: &WalkData) -> bool {
     let is_dot_file = entry.file_name().to_str().unwrap_or("").starts_with('.');
     let is_ignored_path = walk_data.ignore_directories.contains(&entry.path());
+    let follow_links =
+        walk_data.follow_links && entry.file_type().map_or(false, |ft| ft.is_symlink());
 
     if !walk_data.allowed_filesystems.is_empty() {
-        let size_inode_device = get_metadata(entry.path(), false);
+        let size_inode_device = get_metadata(entry.path(), false, follow_links);
         if let Some((_size, Some((_id, dev)), _gunk)) = size_inode_device {
             if !walk_data.allowed_filesystems.contains(&dev) {
                 return true;
@@ -128,7 +130,7 @@ fn ignore_file(entry: &DirEntry, walk_data: &WalkData) -> bool {
         || walk_data.filter_modified_time.is_some()
         || walk_data.filter_changed_time.is_some()
     {
-        let size_inode_device = get_metadata(entry.path(), false);
+        let size_inode_device = get_metadata(entry.path(), false, follow_links);
         if let Some((_, _, (modified_time, accessed_time, changed_time))) = size_inode_device {
             if entry.path().is_file()
                 && [
@@ -251,7 +253,15 @@ fn walk(dir: PathBuf, walk_data: &WalkData, depth: usize) -> Option<Node> {
         }
         vec![]
     };
-    build_node(dir, children, false, false, depth, walk_data)
+    let is_symlink = if walk_data.follow_links {
+        match fs::symlink_metadata(&dir) {
+            Ok(metadata) => metadata.file_type().is_symlink(),
+            Err(_) => false,
+        }
+    } else {
+        false
+    };
+    build_node(dir, children, is_symlink, false, depth, walk_data)
 }
 
 mod tests {

src/main.rs

@@ -228,7 +228,7 @@ fn main() {
     let follow_links = options.get_flag("dereference_links");
 
     let allowed_filesystems = limit_filesystem
-        .then(|| get_filesystem_devices(&target_dirs))
+        .then(|| get_filesystem_devices(&target_dirs, follow_links))
         .unwrap_or_default();
     let simplified_dirs = simplify_dir_names(&target_dirs);
 

src/node.rs

@@ -28,16 +28,16 @@ pub fn build_node(
     let use_apparent_size = walk_data.use_apparent_size;
     let by_filecount = walk_data.by_filecount;
 
-    get_metadata(&dir, use_apparent_size).map(|data| {
-        let inode_device = if is_symlink && !use_apparent_size {
-            None
-        } else {
-            data.1
-        };
+    get_metadata(
+        &dir,
+        use_apparent_size,
+        walk_data.follow_links && is_symlink,
+    )
+    .map(|data| {
+        let inode_device = data.1;
 
         let size = if is_filtered_out_due_to_regex(walk_data.filter_regex, &dir)
             || is_filtered_out_due_to_invert_regex(walk_data.invert_filter_regex, &dir)
-            || (is_symlink && !use_apparent_size)
             || by_filecount && !is_file
             || [
                 (&walk_data.filter_modified_time, data.2 .0),

src/platform.rs

@@ -17,9 +17,15 @@ type FileTime = (i64, i64, i64);
 pub fn get_metadata<P: AsRef<Path>>(
     path: P,
     use_apparent_size: bool,
+    follow_links: bool,
 ) -> Option<(u64, Option<InodeAndDevice>, FileTime)> {
     use std::os::unix::fs::MetadataExt;
-    match path.as_ref().metadata() {
+    let metadata = if follow_links {
+        path.as_ref().metadata()
+    } else {
+        path.as_ref().symlink_metadata()
+    };
+    match metadata {
         Ok(md) => {
             if use_apparent_size {
                 Some((
@@ -43,6 +49,7 @@ pub fn get_metadata<P: AsRef<Path>>(
 pub fn get_metadata<P: AsRef<Path>>(
     path: P,
     use_apparent_size: bool,
+    follow_links: bool,
 ) -> Option<(u64, Option<InodeAndDevice>, FileTime)> {
     // On windows opening the file to get size, file ID and volume can be very
     // expensive because 1) it causes a few system calls, and more importantly 2) it can cause
@@ -142,7 +149,12 @@ pub fn get_metadata<P: AsRef<Path>>(
 
     use std::os::windows::fs::MetadataExt;
     let path = path.as_ref();
-    match path.metadata() {
+    let metadata = if follow_links {
+        path.metadata()
+    } else {
+        path.symlink_metadata()
+    };
+    match metadata {
         Ok(ref md) => {
             const FILE_ATTRIBUTE_ARCHIVE: u32 = 0x20;
             const FILE_ATTRIBUTE_READONLY: u32 = 0x01;

src/utils.rs

@@ -34,13 +34,25 @@ pub fn simplify_dir_names<P: AsRef<Path>>(dirs: &[P]) -> HashSet<PathBuf> {
     top_level_names
 }
 
-pub fn get_filesystem_devices<P: AsRef<Path>>(paths: &[P]) -> HashSet<u64> {
+pub fn get_filesystem_devices<P: AsRef<Path>>(paths: &[P], follow_links: bool) -> HashSet<u64> {
+    use std::fs;
     // Gets the device ids for the filesystems which are used by the argument paths
     paths
         .iter()
-        .filter_map(|p| match get_metadata(p, false) {
-            Some((_size, Some((_id, dev)), _time)) => Some(dev),
-            _ => None,
+        .filter_map(|p| {
+            let follow_links = if follow_links {
+                // slow path: If dereference-links is set, then we check if the file is a symbolic link
+                match fs::symlink_metadata(p) {
+                    Ok(metadata) => metadata.file_type().is_symlink(),
+                    Err(_) => false,
+                }
+            } else {
+                false
+            };
+            match get_metadata(p, false, follow_links) {
+                Some((_size, Some((_id, dev)), _time)) => Some(dev),
+                _ => None,
+            }
         })
         .collect()
 }