Merge pull request #8763 from bakanovskii/df-follow-symlinks

df: follow symlinks

src/uu/df/Cargo.toml

@@ -19,7 +19,7 @@ path = "src/df.rs"
 
 [dependencies]
 clap = { workspace = true }
-uucore = { workspace = true, features = ["libc", "fsext", "parser"] }
+uucore = { workspace = true, features = ["libc", "fsext", "parser", "fs"] }
 unicode-width = { workspace = true }
 thiserror = { workspace = true }
 fluent = { workspace = true }

src/uu/df/src/df.rs

@@ -306,13 +306,24 @@ fn get_all_filesystems(opt: &Options) -> UResult<Vec<Filesystem>> {
     }
 
     let mut mounts = vec![];
-    for mi in read_fs_list()? {
+    for mut mi in read_fs_list()? {
         // TODO The running time of the `is_best()` function is linear
         // in the length of `result`. That makes the running time of
         // this loop quadratic in the length of `vmi`. This could be
         // improved by a more efficient implementation of `is_best()`,
         // but `vmi` is probably not very long in practice.
         if is_included(&mi, opt) && is_best(&mounts, &mi) {
+            let dev_path: &Path = Path::new(&mi.dev_name);
+            if dev_path.is_symlink() {
+                if let Ok(canonicalized_symlink) = uucore::fs::canonicalize(
+                    dev_path,
+                    uucore::fs::MissingHandling::Existing,
+                    uucore::fs::ResolveMode::Logical,
+                ) {
+                    mi.dev_name = canonicalized_symlink.to_string_lossy().to_string();
+                }
+            }
+
             mounts.push(mi);
         }
     }

tests/by-util/test_df.rs

@@ -123,6 +123,22 @@ fn test_df_output() {
     assert_eq!(actual, expected);
 }
 
+#[test]
+fn test_df_follows_symlinks() {
+    let output = new_ucmd!()
+        .arg("-h")
+        .arg("--output=source")
+        .succeeds()
+        .stdout_str_lossy();
+
+    let filesystems = output.lines().skip(1).collect::<Vec<&str>>();
+    assert!(
+        filesystems
+            .iter()
+            .all(|&x| !std::path::Path::new(x).is_symlink())
+    );
+}
+
 #[test]
 fn test_df_output_overridden() {
     let expected = if cfg!(target_os = "macos") {