du: do not deduplicate --files0-from / operand names by name

src/uu/du/src/du.rs

@@ -938,10 +938,11 @@ fn read_files_from(file_name: &OsStr) -> Result<Vec<PathBuf>, std::io::Error> {
             show_error!("{}", translate!("du-error-hyphen-file-name-not-allowed"));
             set_exit_code(1);
         } else {
-            let p = PathBuf::from(&*uucore::os_str_from_bytes(&path).unwrap());
-            if !paths.contains(&p) {
-                paths.push(p);
-            }
+            // Do not deduplicate here: GNU du processes every entry and
+            // relies on inode-based deduplication during traversal (which is
+            // disabled by --count-links). Deduplicating by name would, e.g.,
+            // collapse repeated missing files into a single error.
+            paths.push(PathBuf::from(&*uucore::os_str_from_bytes(&path).unwrap()));
         }
     }
 
@@ -1036,16 +1037,10 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
 
         read_files_from(file_from)?
     } else if let Some(files) = matches.get_many::<OsString>(options::FILE) {
-        let files = files.map(PathBuf::from);
-        if count_links {
-            files.collect()
-        } else {
-            // Deduplicate while preserving order
-            let mut seen = HashSet::default();
-            files
-                .filter(|path| seen.insert(path.clone()))
-                .collect::<Vec<_>>()
-        }
+        // Do not deduplicate by name: GNU du processes every operand and relies
+        // on inode-based deduplication during traversal (disabled by
+        // --count-links), so repeated missing files are reported once each.
+        files.map(PathBuf::from).collect()
     } else {
         vec![PathBuf::from(".")]
     };

tests/by-util/test_du.rs

@@ -1619,6 +1619,38 @@ fn test_du_files0_from_ignore_duplicate_file_names() {
         .stdout_is(format!("0\t{file}\n"));
 }
 
+#[test]
+fn test_du_files0_from_count_links_lists_duplicate_file_names() {
+    // With --count-links (-l), inode-based deduplication is disabled, so a
+    // file listed twice must be reported twice (matches GNU du).
+    let ts = TestScenario::new(util_name!());
+    let at = &ts.fixtures;
+    let file = "testfile";
+
+    at.touch(file);
+    at.write("filelist", &format!("{file}\0{file}\0"));
+
+    ts.ucmd()
+        .arg("-l")
+        .arg("--files0-from=filelist")
+        .succeeds()
+        .stdout_is(format!("0\t{file}\n0\t{file}\n"));
+}
+
+#[test]
+fn test_du_files0_from_repeated_missing_file_reported_each_time() {
+    // Missing files have no inode to deduplicate on, so each occurrence in the
+    // input must produce its own error (matches GNU du).
+    new_ucmd!()
+        .arg("--files0-from=-")
+        .pipe_in("missing\0missing\0")
+        .fails_with_code(1)
+        .stderr_is(
+            "du: cannot access 'missing': No such file or directory\n\
+             du: cannot access 'missing': No such file or directory\n",
+        );
+}
+
 #[test]
 fn test_du_files0_from_with_invalid_zero_length_file_names() {
     let ts = TestScenario::new(util_name!());