fix: Preserve symlinks when running cargo add

Author: RaghavenderSingh

crates/cargo-util/src/paths.rs

@@ -190,14 +190,22 @@ pub fn write<P: AsRef<Path>, C: AsRef<[u8]>>(path: P, contents: C) -> Result<()>
 /// Writes a file to disk atomically.
 ///
 /// This uses `tempfile::persist` to accomplish atomic writes.
+/// If the path is a symlink, it will follow the symlink and write to the actual target.
 pub fn write_atomic<P: AsRef<Path>, C: AsRef<[u8]>>(path: P, contents: C) -> Result<()> {
     let path = path.as_ref();
 
+    // Check if the path is a symlink and follow it if it is
+    let actual_path = if path.is_symlink() {
+        std::fs::read_link(path)?
+    } else {
+        path.to_path_buf()
+    };
+
     // On unix platforms, get the permissions of the original file. Copy only the user/group/other
     // read/write/execute permission bits. The tempfile lib defaults to an initial mode of 0o600,
     // and we'll set the proper permissions after creating the file.
     #[cfg(unix)]
-    let perms = path.metadata().ok().map(|meta| {
+    let perms = actual_path.metadata().ok().map(|meta| {
         use std::os::unix::fs::PermissionsExt;
 
         // these constants are u16 on macOS
@@ -208,8 +216,8 @@ pub fn write_atomic<P: AsRef<Path>, C: AsRef<[u8]>>(path: P, contents: C) -> Res
     });
 
     let mut tmp = TempFileBuilder::new()
-        .prefix(path.file_name().unwrap())
-        .tempfile_in(path.parent().unwrap())?;
+        .prefix(actual_path.file_name().unwrap())
+        .tempfile_in(actual_path.parent().unwrap())?;
     tmp.write_all(contents.as_ref())?;
 
     // On unix platforms, set the permissions on the newly created file. We can use fchmod (called
@@ -220,10 +228,9 @@ pub fn write_atomic<P: AsRef<Path>, C: AsRef<[u8]>>(path: P, contents: C) -> Res
         tmp.as_file().set_permissions(perms)?;
     }
 
-    tmp.persist(path)?;
+    tmp.persist(&actual_path)?;
     Ok(())
 }
-
 /// Equivalent to [`write()`], but does not write anything if the file contents
 /// are identical to the given contents.
 pub fn write_if_changed<P: AsRef<Path>, C: AsRef<[u8]>>(path: P, contents: C) -> Result<()> {

src/cargo/util/toml_mut/manifest.rs

@@ -323,9 +323,9 @@ impl LocalManifest {
         };
         let new_contents_bytes = raw.as_bytes();
 
+        // The symlink handling is now done in write_atomic
         cargo_util::paths::write_atomic(&self.path, new_contents_bytes)
     }
-
     /// Lookup a dependency.
     pub fn get_dependency_versions<'s>(
         &'s self,