chore: Rust 1.89 promoted file locking to the standard library, so prefer stdlib to fs2 (#2467)

---
[//]: # (BEGIN SAPLING FOOTER)
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* __->__ #2467
* #2465

codex-rs/Cargo.lock

@@ -703,7 +703,6 @@ dependencies = [
  "dirs",
  "env-flags",
  "eventsource-stream",
- "fs2",
  "futures",
  "landlock",
  "libc",
@@ -1745,16 +1744,6 @@ dependencies = [
  "percent-encoding",
 ]
 
-[[package]]
-name = "fs2"
-version = "0.4.3"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9564fc758e15025b46aa6643b1b77d047d1a56a1aea6e01002ac0c7026876213"
-dependencies = [
- "libc",
- "winapi",
-]
-
 [[package]]
 name = "futures"
 version = "0.3.31"

codex-rs/core/Cargo.toml

@@ -23,7 +23,6 @@ codex-protocol = { path = "../protocol" }
 dirs = "6"
 env-flags = "0.1.1"
 eventsource-stream = "0.2.3"
-fs2 = "0.4.3"
 futures = "0.3"
 libc = "0.2.175"
 mcp-types = { path = "../mcp-types" }

codex-rs/core/src/message_history.rs

@@ -125,16 +125,18 @@ pub(crate) async fn append_entry(text: &str, session_id: &Uuid, config: &Config)
 /// times if the lock is currently held by another process. This prevents a
 /// potential indefinite wait while still giving other writers some time to
 /// finish their operation.
-async fn acquire_exclusive_lock_with_retry(file: &std::fs::File) -> Result<()> {
+async fn acquire_exclusive_lock_with_retry(file: &File) -> Result<()> {
     use tokio::time::sleep;
 
     for _ in 0..MAX_RETRIES {
-        match fs2::FileExt::try_lock_exclusive(file) {
+        match file.try_lock() {
             Ok(()) => return Ok(()),
-            Err(e) if e.kind() == std::io::ErrorKind::WouldBlock => {
+            Err(e) => match e {
+                std::fs::TryLockError::WouldBlock => {
                     sleep(RETRY_SLEEP).await;
                 }
-            Err(e) => return Err(e),
+                other => return Err(other.into()),
+            },
         }
     }
 
@@ -259,12 +261,14 @@ pub(crate) fn lookup(log_id: u64, offset: usize, config: &Config) -> Option<Hist
 #[cfg(unix)]
 fn acquire_shared_lock_with_retry(file: &File) -> Result<()> {
     for _ in 0..MAX_RETRIES {
-        match fs2::FileExt::try_lock_shared(file) {
+        match file.try_lock_shared() {
             Ok(()) => return Ok(()),
-            Err(e) if e.kind() == std::io::ErrorKind::WouldBlock => {
+            Err(e) => match e {
+                std::fs::TryLockError::WouldBlock => {
                     std::thread::sleep(RETRY_SLEEP);
                 }
-            Err(e) => return Err(e),
+                other => return Err(other.into()),
+            },
         }
     }