test_tail: add tests for --follow=name --disable-inotify (polling)

src/uu/tail/src/tail.rs

@@ -390,6 +390,7 @@ fn follow(readers: &mut Vec<(Box<dyn BufRead>, &PathBuf)>, settings: &Settings)
                                     // notify::EventKind::Any => {}
                                     // EventKind::Access(AccessKind::Close(AccessMode::Write)) => {}
                                     EventKind::Create(CreateKind::File)
+                                    | EventKind::Create(CreateKind::Any)
                                     | EventKind::Modify(ModifyKind::Name(RenameMode::To)) => {
                                         // This triggers for e.g.:
                                         // Create: cp log.bak log.dat
@@ -423,6 +424,7 @@ fn follow(readers: &mut Vec<(Box<dyn BufRead>, &PathBuf)>, settings: &Settings)
                                     // EventKind::Modify(ModifyKind::Name(RenameMode::From)) => {}
                                     // EventKind::Modify(ModifyKind::Name(RenameMode::To)) => {}
                                     EventKind::Remove(RemoveKind::File)
+                                    | EventKind::Remove(RemoveKind::Any)
                                     | EventKind::Modify(ModifyKind::Name(RenameMode::From)) => {
                                         // This triggers for e.g.:
                                         // Create: cp log.dat log.bak

tests/by-util/test_tail.rs

@@ -521,6 +521,51 @@ fn test_follow_name_create() {
     assert_eq!(buf_stderr, expected_stderr);
 }
 
+#[test]
+fn test_follow_name_create_polling() {
+    // This test triggers a remove/create event while `tail --follow=name --disable-inotify logfile` is running.
+    // cp logfile backup && rm logfile && sleep 1 && cp backup logfile
+
+    let ts = TestScenario::new(util_name!());
+    let at = &ts.fixtures;
+
+    let source = FOLLOW_NAME_TXT;
+    let source_canonical = &at.plus(source);
+    let backup = at.plus_as_string("backup");
+
+    let expected_stdout = at.read(FOLLOW_NAME_EXP);
+    let expected_stderr = format!(
+        "{}: '{}' has been replaced;  following new file\n",
+        ts.util_name, source
+    );
+
+    let args = ["--follow=name", "--disable-inotify", source];
+    let mut p = ts.ucmd().args(&args).run_no_wait();
+
+    let delay = 750;
+
+    std::fs::copy(&source_canonical, &backup).unwrap();
+    sleep(Duration::from_millis(delay));
+
+    std::fs::remove_file(source_canonical).unwrap();
+    sleep(Duration::from_millis(delay));
+
+    std::fs::copy(&backup, &source_canonical).unwrap();
+    sleep(Duration::from_millis(delay));
+
+    p.kill().unwrap();
+
+    let mut buf_stdout = String::new();
+    let mut p_stdout = p.stdout.take().unwrap();
+    p_stdout.read_to_string(&mut buf_stdout).unwrap();
+    assert_eq!(buf_stdout, expected_stdout);
+
+    let mut buf_stderr = String::new();
+    let mut p_stderr = p.stderr.take().unwrap();
+    p_stderr.read_to_string(&mut buf_stderr).unwrap();
+    assert_eq!(buf_stderr, expected_stderr);
+}
+
 #[test]
 fn test_follow_name_move() {
     // This test triggers a move event while `tail --follow=name logfile` is running.
@@ -563,3 +608,46 @@ fn test_follow_name_move() {
     p_stderr.read_to_string(&mut buf_stderr).unwrap();
     assert_eq!(buf_stderr, expected_stderr);
 }
+
+#[test]
+fn test_follow_name_move_polling() {
+    // This test triggers a move event while `tail --follow=name --disable-inotify logfile` is running.
+    // mv logfile backup && sleep 1 && mv backup file
+
+    let ts = TestScenario::new(util_name!());
+    let at = &ts.fixtures;
+
+    let source = FOLLOW_NAME_TXT;
+    let source_canonical = &at.plus(source);
+    let backup = at.plus_as_string("backup");
+
+    let expected_stdout = at.read("follow_name.expected");
+    let expected_stderr = format!(
+        "{}: '{}' has been replaced;  following new file\n",
+        ts.util_name, source
+    );
+
+    let args = ["--follow=name", "--disable-inotify", source];
+    let mut p = ts.ucmd().args(&args).run_no_wait();
+
+    let delay = 750;
+
+    sleep(Duration::from_millis(delay));
+    std::fs::rename(&source_canonical, &backup).unwrap();
+    sleep(Duration::from_millis(delay));
+
+    std::fs::rename(&backup, &source_canonical).unwrap();
+    sleep(Duration::from_millis(delay));
+
+    p.kill().unwrap();
+
+    let mut buf_stdout = String::new();
+    let mut p_stdout = p.stdout.take().unwrap();
+    p_stdout.read_to_string(&mut buf_stdout).unwrap();
+    assert_eq!(buf_stdout, expected_stdout);
+
+    let mut buf_stderr = String::new();
+    let mut p_stderr = p.stderr.take().unwrap();
+    p_stderr.read_to_string(&mut buf_stderr).unwrap();
+    assert_eq!(buf_stderr, expected_stderr);
+}