project: Fix empty files not downloading from a remote project (#51571)

Amaan created 3 weeks ago

- check `content_size==0`
- entry is removed from `downloading_files`
- empty file is writte via `smol::fs::write(..., &[])`

this means the receiver handles the empty files completely as soon as
the State message arrives, without ever needing a Chunk that will never
come

Closes #51551

Before you mark this PR as ready for review, make sure that you have:
- [x] Added a solid test coverage and/or screenshots from doing manual
testing
- [x] Done a self-review taking into account security and performance
aspects
- [ ] No UI CHANGES


Release Notes:
- Fixed empty files not downloading from a remote project

Change summary

crates/project/src/project.rs | 58 ++++++++++++++++++++++++++----------
1 file changed, 42 insertions(+), 16 deletions(-)

Detailed changes

crates/project/src/project.rs

@@ -5497,25 +5497,51 @@ impl Project {
                     let key = (worktree_id, path);
                     log::debug!("handle_create_file_for_peer: looking up key={:?}", key);
 
-                    let mut files = downloading_files.lock();
-                    log::trace!(
-                        "handle_create_file_for_peer: current downloading_files keys: {:?}",
-                        files.keys().collect::<Vec<_>>()
-                    );
+                    let empty_file_destination: Option<PathBuf> = {
+                        let mut files = downloading_files.lock();
+                        log::trace!(
+                            "handle_create_file_for_peer: current downloading_files keys: {:?}",
+                            files.keys().collect::<Vec<_>>()
+                        );
+
+                        if let Some(file_entry) = files.get_mut(&key) {
+                            file_entry.total_size = state.content_size;
+                            file_entry.file_id = Some(state.id);
+                            log::debug!(
+                                "handle_create_file_for_peer: updated file entry: total_size={}, file_id={}",
+                                state.content_size,
+                                state.id
+                            );
+                        } else {
+                            log::warn!(
+                                "handle_create_file_for_peer: key={:?} not found in downloading_files",
+                                key
+                            );
+                        }
+
+                        if state.content_size == 0 {
+                            // No chunks will arrive for an empty file; write it now.
+                            files.remove(&key).map(|entry| entry.destination_path)
+                        } else {
+                            None
+                        }
+                    };
 
-                    if let Some(file_entry) = files.get_mut(&key) {
-                        file_entry.total_size = state.content_size;
-                        file_entry.file_id = Some(state.id);
+                    if let Some(destination) = empty_file_destination {
                         log::debug!(
-                            "handle_create_file_for_peer: updated file entry: total_size={}, file_id={}",
-                            state.content_size,
-                            state.id
-                        );
-                    } else {
-                        log::warn!(
-                            "handle_create_file_for_peer: key={:?} not found in downloading_files",
-                            key
+                            "handle_create_file_for_peer: writing empty file to {:?}",
+                            destination
                         );
+                        match smol::fs::write(&destination, &[] as &[u8]).await {
+                            Ok(_) => log::info!(
+                                "handle_create_file_for_peer: successfully wrote file to {:?}",
+                                destination
+                            ),
+                            Err(e) => log::error!(
+                                "handle_create_file_for_peer: failed to write empty file: {:?}",
+                                e
+                            ),
+                        }
                     }
                 } else {
                     log::warn!("handle_create_file_for_peer: State has no file field");