readlink: symlink loop handling (#3717)

readlink: fix symlink loop handling

src/uu/readlink/src/readlink.rs

@@ -84,7 +84,8 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
                 if verbose {
                     return Err(USimpleError::new(
                         1,
-                        format!("{}: errno {}", f.maybe_quote(), err.raw_os_error().unwrap()),
+                        err.map_err_context(move || f.maybe_quote().to_string())
+                            .to_string(),
                     ));
                 } else {
                     return Err(1.into());

tests/by-util/test_readlink.rs

@@ -70,3 +70,13 @@ fn test_long_redirection_to_root() {
     println!("expect: {:?}", expect);
     assert_eq!(actual, expect);
 }
+
+#[test]
+fn test_symlink_to_itself_verbose() {
+    let (at, mut ucmd) = at_and_ucmd!();
+    at.relative_symlink_file("a", "a");
+    ucmd.args(&["-ev", "a"])
+        .fails()
+        .code_is(1)
+        .stderr_contains("Too many levels of symbolic links");
+}