Preserve symlinks in file copy

Cargo.lock

@@ -436,7 +436,7 @@ dependencies = [
 
 [[package]]
 name = "dosh"
-version = "1.0.0-rc26"
+version = "1.0.0-rc27"
 dependencies = [
  "anyhow",
  "base64",

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "dosh"
-version = "1.0.0-rc26"
+version = "1.0.0-rc27"
 edition = "2024"
 license = "MIT"
 

src/bin/dosh-client.rs

@@ -1866,6 +1866,30 @@ impl FileServiceClient {
             other => bail!("unexpected mkdir response: {other:?}"),
         }
     }
+
+    fn readlink(&mut self, path: &str) -> Result<String> {
+        self.send(FileRequest::Readlink {
+            path: path.to_string(),
+        })?;
+        match self.recv()? {
+            FileResponse::LinkTarget { target } => Ok(target),
+            FileResponse::Error { message } => Err(anyhow!(message)),
+            other => bail!("unexpected readlink response: {other:?}"),
+        }
+    }
+
+    fn symlink(&mut self, path: &str, target: &str, overwrite: bool) -> Result<()> {
+        self.send(FileRequest::Symlink {
+            path: path.to_string(),
+            target: target.to_string(),
+            overwrite,
+        })?;
+        match self.recv()? {
+            FileResponse::Ok => Ok(()),
+            FileResponse::Error { message } => Err(anyhow!(message)),
+            other => bail!("unexpected symlink response: {other:?}"),
+        }
+    }
 }
 
 fn run_cp_command(_config: &dosh::config::ClientConfig, args: &Args) -> Result<()> {
@@ -2197,6 +2221,18 @@ fn upload_path(
     let metadata =
         fs::symlink_metadata(local).with_context(|| format!("stat {}", local.display()))?;
     let remote = upload_destination(client, local, remote, metadata.is_dir())?;
+    if metadata.file_type().is_symlink() {
+        let target =
+            fs::read_link(local).with_context(|| format!("readlink {}", local.display()))?;
+        let target = target
+            .to_str()
+            .ok_or_else(|| anyhow!("symlink target is not valid UTF-8: {}", local.display()))?;
+        client.symlink(&remote, target, opts.overwrite)?;
+        if opts.progress {
+            eprintln!("linked {} -> {}", remote, target);
+        }
+        return Ok(());
+    }
     if metadata.is_dir() {
         anyhow::ensure!(
             opts.recursive,
@@ -2343,8 +2379,9 @@ fn download_path(
             Ok(())
         }
         FileKind::File => download_file(client, remote, &destination, &meta, opts),
+        FileKind::Symlink => download_symlink(client, remote, &destination, opts),
         _ => Err(anyhow!(
-            "remote path is not a regular file or directory: {remote}"
+            "remote path is not a regular file, directory, or symlink: {remote}"
         )),
     }
 }
@@ -2377,8 +2414,16 @@ fn copy_remote_path(
             Ok(())
         }
         FileKind::File => copy_remote_file(src_client, dst_client, src, &dst, &meta, opts),
+        FileKind::Symlink => {
+            let target = src_client.readlink(src)?;
+            dst_client.symlink(&dst, &target, opts.overwrite)?;
+            if opts.progress {
+                eprintln!("linked {dst} -> {target}");
+            }
+            Ok(())
+        }
         _ => Err(anyhow!(
-            "remote path is not a regular file or directory: {src}"
+            "remote path is not a regular file, directory, or symlink: {src}"
         )),
     }
 }
@@ -2609,6 +2654,45 @@ fn download_file(
     }
 }
 
+fn download_symlink(
+    client: &mut FileServiceClient,
+    remote: &str,
+    local: &Path,
+    opts: &CpOptions,
+) -> Result<()> {
+    if let Some(parent) = local.parent()
+        && !parent.as_os_str().is_empty()
+    {
+        fs::create_dir_all(parent).with_context(|| format!("create {}", parent.display()))?;
+    }
+    let target = client.readlink(remote)?;
+    create_local_symlink(local, &target, opts.overwrite)?;
+    if opts.progress {
+        eprintln!("linked {} -> {}", local.display(), target);
+    }
+    Ok(())
+}
+
+#[cfg(unix)]
+fn create_local_symlink(path: &Path, target: &str, overwrite: bool) -> Result<()> {
+    if let Ok(metadata) = fs::symlink_metadata(path) {
+        anyhow::ensure!(overwrite, "destination exists: {}", path.display());
+        anyhow::ensure!(
+            !metadata.is_dir(),
+            "destination is a directory: {}",
+            path.display()
+        );
+        fs::remove_file(path).with_context(|| format!("remove {}", path.display()))?;
+    }
+    std::os::unix::fs::symlink(target, path)
+        .with_context(|| format!("symlink {} -> {}", path.display(), target))
+}
+
+#[cfg(not(unix))]
+fn create_local_symlink(_path: &Path, _target: &str, _overwrite: bool) -> Result<()> {
+    bail!("symlink creation is not supported on this client platform")
+}
+
 fn hash_prefix(file: &mut fs::File, bytes: u64, hasher: &mut Sha256) -> Result<()> {
     file.seek(std::io::SeekFrom::Start(0))?;
     let mut remaining = bytes;

src/bin/dosh-server.rs

@@ -2681,6 +2681,46 @@ async fn handle_file_request(
             send_file_response_to_client(state, socket, client_id, stream_id, FileResponse::Ok)
                 .await
         }
+        FileRequest::Readlink { path } => {
+            let path = clean_remote_path(&path, home)?;
+            let target =
+                fs::read_link(&path).with_context(|| format!("readlink {}", path.display()))?;
+            let target = target
+                .to_str()
+                .ok_or_else(|| anyhow!("symlink target is not valid UTF-8"))?
+                .to_string();
+            send_file_response_to_client(
+                state,
+                socket,
+                client_id,
+                stream_id,
+                FileResponse::LinkTarget { target },
+            )
+            .await
+        }
+        FileRequest::Symlink {
+            path,
+            target,
+            overwrite,
+        } => {
+            let path = clean_remote_path(&path, home)?;
+            if let Some(parent) = path.parent() {
+                fs::create_dir_all(parent)
+                    .with_context(|| format!("create {}", parent.display()))?;
+            }
+            if let Ok(metadata) = fs::symlink_metadata(&path) {
+                anyhow::ensure!(overwrite, "destination exists: {}", path.display());
+                anyhow::ensure!(
+                    !metadata.is_dir(),
+                    "destination is a directory: {}",
+                    path.display()
+                );
+                fs::remove_file(&path).with_context(|| format!("remove {}", path.display()))?;
+            }
+            create_symlink(&target, &path)?;
+            send_file_response_to_client(state, socket, client_id, stream_id, FileResponse::Ok)
+                .await
+        }
         FileRequest::Remove { path, recursive } => {
             let path = clean_remote_path(&path, home)?;
             let metadata =
@@ -3065,6 +3105,17 @@ fn set_mode(path: &Path, mode: u32) -> Result<()> {
     fs::set_permissions(path, permissions).with_context(|| format!("chmod {}", path.display()))
 }
 
+#[cfg(unix)]
+fn create_symlink(target: &str, path: &Path) -> Result<()> {
+    std::os::unix::fs::symlink(target, path)
+        .with_context(|| format!("symlink {} -> {}", path.display(), target))
+}
+
+#[cfg(not(unix))]
+fn create_symlink(_target: &str, _path: &Path) -> Result<()> {
+    bail!("symlink creation is not supported on this server platform")
+}
+
 fn upload_temp_path(final_path: &Path, stream_id: u64) -> PathBuf {
     let name = final_path
         .file_name()

src/file_transfer.rs

@@ -18,6 +18,14 @@ pub enum FileRequest {
         path: String,
         mode: Option<u32>,
     },
+    Readlink {
+        path: String,
+    },
+    Symlink {
+        path: String,
+        target: String,
+        overwrite: bool,
+    },
     Remove {
         path: String,
         recursive: bool,
@@ -56,6 +64,9 @@ pub enum FileResponse {
     List {
         entries: Vec<FileEntry>,
     },
+    LinkTarget {
+        target: String,
+    },
     Start {
         meta: FileMeta,
         offset: u64,

tests/integration_smoke.rs

@@ -1003,6 +1003,8 @@ fn native_file_copy_recursive_round_trip() {
     fs::create_dir_all(src.join("nested")).unwrap();
     fs::write(src.join("root.txt"), b"root file\n").unwrap();
     fs::write(src.join("nested/child.txt"), b"child file\n").unwrap();
+    std::os::unix::fs::symlink("root.txt", src.join("root-link")).unwrap();
+    std::os::unix::fs::symlink("nested/child.txt", src.join("child-link")).unwrap();
 
     let client_bin = env!("CARGO_BIN_EXE_dosh-client");
     let upload = Command::new(client_bin)
@@ -1108,6 +1110,14 @@ fn native_file_copy_recursive_round_trip() {
         fs::read_to_string(downloaded.join("nested/child.txt")).unwrap(),
         "child file\n"
     );
+    assert_eq!(
+        fs::read_link(downloaded.join("root-link")).unwrap(),
+        PathBuf::from("root.txt")
+    );
+    assert_eq!(
+        fs::read_link(downloaded.join("child-link")).unwrap(),
+        PathBuf::from("nested/child.txt")
+    );
 
     let remove = Command::new(client_bin)
         .arg("--dosh-host")