tail: print inaccessible message when symlink target changes

src/uu/tail/locales/en-US.ftl

@@ -73,5 +73,6 @@ tail-no-files-remaining = no files remaining
 tail-become-inaccessible = has become inaccessible
 
 # Debug messages
+tail-debug-using-blocking-mode = using blocking mode
 tail-debug-using-notification-mode = using notification mode
 tail-debug-using-polling-mode = using polling mode

src/uu/tail/locales/fr-FR.ftl

@@ -70,3 +70,8 @@ tail-giving-up-on-this-name = ; abandon de ce nom
 tail-stdin-header = entrée standard
 tail-no-files-remaining = aucun fichier restant
 tail-become-inaccessible = est devenu inaccessible
+
+# Messages de débogage
+tail-debug-using-blocking-mode = utilisation du mode bloquant
+tail-debug-using-notification-mode = utilisation du mode notification
+tail-debug-using-polling-mode = utilisation du mode sondage

src/uu/tail/src/follow/watch.rs

@@ -381,6 +381,14 @@ impl Observer {
                     }
                     self.files.update_metadata(event_path, Some(new_md));
                 } else if event_path.is_symlink() && settings.retry {
+                    if let Some(old_md) = self.files.get_mut_metadata(event_path) {
+                        if old_md.is_tailable() && self.files.get(event_path).reader.is_some() {
+                            show_error!(
+                                "{}",
+                                translate!("tail-status-file-became-inaccessible", "file" => display_name.quote(), "become_inaccessible" => translate!("tail-become-inaccessible"), "no_such_file" => translate!("tail-no-such-file-or-directory"))
+                            );
+                        }
+                    }
                     self.files.reset_reader(event_path);
                     self.orphans.push(event_path.clone());
                 }

src/uu/tail/src/tail.rs

@@ -22,7 +22,7 @@ mod platform;
 pub mod text;
 
 pub use args::uu_app;
-use args::{FilterMode, Settings, Signum, parse_args};
+use args::{FilterMode, FollowMode, Settings, Signum, parse_args};
 use chunks::ReverseChunks;
 use follow::Observer;
 use memchr::{memchr_iter, memrchr_iter};
@@ -68,8 +68,14 @@ fn uu_tail(settings: &Settings) -> UResult<()> {
 
     // Print debug info about the follow implementation being used
     if settings.debug && settings.follow.is_some() {
-        if observer.use_polling {
+        let all_non_regular = settings
+            .inputs
+            .iter()
+            .all(|i| !matches!(i.kind(), InputKind::File(p) if p.is_file()));
+        if observer.use_polling || (all_non_regular && settings.follow == Some(FollowMode::Name)) {
             show_error!("{}", translate!("tail-debug-using-polling-mode"));
+        } else if all_non_regular {
+            show_error!("{}", translate!("tail-debug-using-blocking-mode"));
         } else {
             show_error!("{}", translate!("tail-debug-using-notification-mode"));
         }

tests/by-util/test_tail.rs

@@ -5133,6 +5133,50 @@ fn test_debug_flag_with_polling() {
         .stderr_contains("tail: using polling mode");
 }
 
+#[test]
+#[cfg(target_os = "linux")]
+fn test_debug_flag_blocking_mode_non_regular() {
+    let mut child = new_ucmd!()
+        .args(&["--debug", "-f", "/dev/null"])
+        .run_no_wait();
+    child.make_assertion_with_delay(500).is_alive();
+    child
+        .kill()
+        .make_assertion()
+        .with_all_output()
+        .stderr_contains("tail: using blocking mode");
+}
+
+#[test]
+#[cfg(target_os = "linux")]
+fn test_debug_flag_polling_mode_non_regular_follow_name() {
+    let mut child = new_ucmd!()
+        .args(&["--debug", "-F", "/dev/null"])
+        .run_no_wait();
+    child.make_assertion_with_delay(500).is_alive();
+    child
+        .kill()
+        .make_assertion()
+        .with_all_output()
+        .stderr_contains("tail: using polling mode");
+}
+
+#[test]
+#[cfg(target_os = "linux")]
+fn test_debug_flag_notification_mode_regular_follow_name() {
+    let ts = TestScenario::new(util_name!());
+    let at = &ts.fixtures;
+    at.touch("f");
+
+    let mut child = ts.ucmd().args(&["--debug", "-F", "f"]).run_no_wait();
+    child.make_assertion_with_delay(500).is_alive();
+    child
+        .kill()
+        .make_assertion()
+        .with_all_output()
+        .stderr_contains("tail: using notification mode");
+}
+
 #[test]
 #[cfg(target_os = "linux")]
 fn test_debug_flag_with_inotify() {