remove symlinks at target to avoid issue with invalid symlinks at target

Author: cre4ture

src/uu/install/src/install.rs

@@ -12,13 +12,13 @@ use file_diff::diff;
 use filetime::{set_file_times, FileTime};
 use std::error::Error;
 use std::fmt::{Debug, Display};
-use std::fs;
 use std::fs::File;
 use std::os::unix::fs::MetadataExt;
 #[cfg(unix)]
 use std::os::unix::prelude::OsStrExt;
 use std::path::{Path, PathBuf, MAIN_SEPARATOR};
 use std::process;
+use std::{fs, io};
 use uucore::backup_control::{self, BackupMode};
 use uucore::display::Quotable;
 use uucore::entries::{grp2gid, usr2uid};
@@ -736,6 +736,18 @@ fn perform_backup(to: &Path, b: &Behavior) -> UResult<Option<PathBuf>> {
     }
 }
 
+fn copy_file_source_not_dev_null(from: &Path, to: &Path) -> io::Result<()> {
+    let dest_meta_res = fs::symlink_metadata(to);
+    if let Ok(dest_meta) = dest_meta_res {
+        if dest_meta.is_symlink() {
+            // fs::copy fails if destination is a invalid symlink
+            // so lets just remove all symlinks at destination before copy
+            fs::remove_file(to)?;
+        }
+    }
+    fs::copy(from, to).map(|_| ())
+}
+
 /// Copy a file from one path to another.
 ///
 /// # Parameters
@@ -757,8 +769,13 @@ fn copy_file(from: &Path, to: &Path) -> UResult<()> {
                 InstallError::InstallFailed(from.to_path_buf(), to.to_path_buf(), err).into(),
             );
         }
-    } else if let Err(err) = fs::copy(from, to) {
-        return Err(InstallError::InstallFailed(from.to_path_buf(), to.to_path_buf(), err).into());
+    } else {
+        let result = copy_file_source_not_dev_null(from, to);
+        if let Err(err) = result {
+            return Err(
+                InstallError::InstallFailed(from.to_path_buf(), to.to_path_buf(), err).into(),
+            );
+        }
     }
     Ok(())
 }

tests/by-util/test_install.rs

@@ -702,6 +702,37 @@ fn test_install_and_strip_with_program_hyphen() {
         .no_stderr();
 }
 
+#[cfg(all(unix, feature = "chmod"))]
+#[test]
+// FixME: Freebsd fails on 'No such file or directory'
+#[cfg(not(target_os = "freebsd"))]
+fn test_install_on_invalid_link_at_destination() {
+    let scene = TestScenario::new(util_name!());
+
+    let at = &scene.fixtures;
+    at.mkdir("src");
+    at.mkdir("dest");
+    let src_dir = at.plus("src");
+    let dst_dir = at.plus("dest");
+
+    at.touch("test.sh");
+    at.symlink_file(
+        "/opt/FakeDestination",
+        &dst_dir.join("test.sh").to_string_lossy(),
+    );
+    scene.ccmd("chmod").arg("+x").arg("test.sh").succeeds();
+    at.symlink_file("test.sh", &src_dir.join("test.sh").to_string_lossy());
+
+    scene
+        .ucmd()
+        .current_dir(&src_dir)
+        .arg(src_dir.join("test.sh"))
+        .arg(dst_dir.join("test.sh"))
+        .succeeds()
+        .no_stderr()
+        .no_stdout();
+}
+
 #[test]
 #[cfg(not(windows))]
 fn test_install_and_strip_with_invalid_program() {