From 54efd400722e8f3c41c9cdc34d63867f5469268c Mon Sep 17 00:00:00 2001
From: Nicholas Yang <nicholas.yang@vercel.com>
Date: Wed, 6 Nov 2024 13:39:32 -0500
Subject: [PATCH] chore(daemon): lazy load package changes watcher (#9396)

### Description

Before we'd initialize the package changes watcher when the daemon
starts up. Now we do it only when watch mode needs it.

### Testing Instructions

Tested manually:

```
cargo run -p turbo -- --cwd ../my-turborepo --skip-infer daemon restart
```
In different terminal:
```
cargo run -p turbo -- --cwd ../my-turborepo --skip-infer daemon logs
```

Change a file in the repository, note that no logs are emitted for this
change.

Then run

```
turbo watch dev
```

Note that package changes start showing up.
---
 crates/turborepo-lib/src/daemon/server.rs | 29 +++++++++++++++--------
 1 file changed, 19 insertions(+), 10 deletions(-)

diff --git a/crates/turborepo-lib/src/daemon/server.rs b/crates/turborepo-lib/src/daemon/server.rs
index 675865d877ad3..5d8465d49eed0 100644
--- a/crates/turborepo-lib/src/daemon/server.rs
+++ b/crates/turborepo-lib/src/daemon/server.rs
@@ -7,7 +7,7 @@ use std::{
     collections::{HashMap, HashSet},
     sync::{
         atomic::{AtomicBool, Ordering},
-        Arc, Mutex,
+        Arc, Mutex, OnceLock,
     },
     time::{Duration, Instant},
 };
@@ -61,10 +61,11 @@ pub enum CloseReason {
 /// a general API and close this up.
 #[derive(Clone)]
 pub struct FileWatching {
+    repo_root: AbsoluteSystemPathBuf,
     watcher: Arc<FileSystemWatcher>,
     pub glob_watcher: Arc<GlobWatcher>,
     pub package_watcher: Arc<PackageWatcher>,
-    pub package_changes_watcher: Arc<PackageChangesWatcher>,
+    pub package_changes_watcher: OnceLock<Arc<PackageChangesWatcher>>,
     pub hash_watcher: Arc<HashWatcher>,
 }
 
@@ -136,20 +137,28 @@ impl FileWatching {
             scm,
         ));
 
-        let package_changes_watcher = Arc::new(PackageChangesWatcher::new(
-            repo_root,
-            recv.clone(),
-            hash_watcher.clone(),
-        ));
-
         Ok(FileWatching {
+            repo_root,
             watcher,
             glob_watcher,
             package_watcher,
-            package_changes_watcher,
+            package_changes_watcher: OnceLock::new(),
             hash_watcher,
         })
     }
+
+    pub fn get_or_init_package_changes_watcher(&self) -> Arc<PackageChangesWatcher> {
+        self.package_changes_watcher
+            .get_or_init(|| {
+                let recv = self.watcher.watch();
+                Arc::new(PackageChangesWatcher::new(
+                    self.repo_root.clone(),
+                    recv,
+                    self.hash_watcher.clone(),
+                ))
+            })
+            .clone()
+    }
 }
 
 /// Timeout for every RPC the server handles
@@ -591,7 +600,7 @@ impl proto::turbod_server::Turbod for TurboGrpcServiceInner {
     ) -> Result<tonic::Response<Self::PackageChangesStream>, tonic::Status> {
         let mut package_changes_rx = self
             .file_watching
-            .package_changes_watcher
+            .get_or_init_package_changes_watcher()
             .package_changes()
             .await;