ln: add error handling for hard link creation on directories

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

@@ -35,4 +35,5 @@ ln-prompt-replace = replace {$file}?
 ln-cannot-backup = cannot backup {$file}
 ln-failed-to-access = failed to access {$file}
 ln-failed-to-create-hard-link = failed to create hard link {$source} => {$dest}
+ln-failed-to-create-hard-link-dir = {$source}: hard link not allowed for directory
 ln-backup = backup: {$backup}

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

@@ -36,4 +36,5 @@ ln-prompt-replace = remplacer {$file} ?
 ln-cannot-backup = impossible de sauvegarder {$file}
 ln-failed-to-access = échec d'accès à {$file}
 ln-failed-to-create-hard-link = échec de création du lien physique {$source} => {$dest}
+ln-failed-to-create-hard-link-dir = {$source} : lien physique non autorisé pour un répertoire
 ln-backup = sauvegarde : {$backup}

src/uu/ln/src/ln.rs

@@ -62,6 +62,9 @@ enum LnError {
 
     #[error("{}", translate!("ln-error-extra-operand", "operand" => _0.to_string_lossy(), "program" => _1.clone()))]
     ExtraOperand(OsString, String),
+
+    #[error("{}", translate!("ln-failed-to-create-hard-link-dir", "source" => _0.to_string_lossy()))]
+    FailedToCreateHardLinkDir(PathBuf),
 }
 
 impl UError for LnError {
@@ -431,6 +434,12 @@ fn link(src: &Path, dst: &Path, settings: &Settings) -> UResult<()> {
     if settings.symbolic {
         symlink(&source, dst)?;
     } else {
+        // Cannot create hard link to a directory directly
+        // We can however create hard link to a symlink that points to a directory, so long as -L is not passed
+        if src.is_dir() && (!src.is_symlink() || settings.logical) {
+            return Err(LnError::FailedToCreateHardLinkDir(source.to_path_buf()).into());
+        }
+
         let p = if settings.logical && source.is_symlink() {
             // if we want to have an hard link,
             // source is a symlink and -L is passed

tests/by-util/test_ln.rs

@@ -934,3 +934,17 @@ fn test_ln_non_utf8_paths() {
     let symlink_path = at.plus(symlink_name);
     assert!(symlink_path.is_symlink());
 }
+
+#[test]
+fn test_ln_hard_link_dir() {
+    let scene = TestScenario::new(util_name!());
+    let at = &scene.fixtures;
+
+    at.mkdir("dir");
+
+    scene
+        .ucmd()
+        .args(&["dir", "dir_link"])
+        .fails()
+        .stderr_contains("hard link not allowed for directory");
+}

util/build-gnu.sh

@@ -268,9 +268,6 @@ sed -i -e "s/cat opts/sed -i -e \"s| <.\*$||g\" opts/" tests/misc/usage_vs_getop
 # for some reasons, some stuff are duplicated, strip that
 sed -i -e "s/provoked error./provoked error\ncat pat |sort -u > pat/" tests/misc/usage_vs_getopt.sh
 
-# Update the GNU error message to match ours
-sed -i -e "s/link-to-dir: hard link not allowed for directory/failed to create hard link 'link-to-dir' =>/" -e "s|link-to-dir/: hard link not allowed for directory|failed to create hard link 'link-to-dir/' =>|" tests/ln/hard-to-sym.sh
-
 # install verbose messages shows ginstall as command
 sed -i -e "s/ginstall: creating directory/install: creating directory/g" tests/install/basic-1.sh