refactor(hydro_lang): use fs2 file locking to fix stable build testing #1780 (#1816)

rust-lang/rust#130994

Also configures betterToml formatting

---------

Co-authored-by: Copilot <[email protected]>

This PR refactors file locking in the hydro_lang deployment code to use fs2 for non-nightly builds, addressing stability issues in build testing.  
- Always create the project lock file regardless of the Rust channel  
- Use fs2 file locking for non-nightly builds while retaining the original nightly locking  
- Add a non-nightly fs2 dependency configuration in Cargo.toml

Author: MingweiSamuel

.vscode/settings.json

@@ -23,4 +23,16 @@
     "files.watcherExclude": {
         "**/target": true
     },
-}
+    "evenBetterToml.formatter.columnWidth": 80,
+    "evenBetterToml.formatter.compactArrays": true,
+    "evenBetterToml.formatter.allowedBlankLines": 2,
+    "evenBetterToml.formatter.trailingNewline": true,
+    "evenBetterToml.formatter.arrayAutoCollapse": true,
+    "evenBetterToml.formatter.arrayAutoExpand": true,
+    "evenBetterToml.formatter.arrayTrailingComma": true,
+    "evenBetterToml.formatter.compactEntries": false,
+    "evenBetterToml.formatter.compactInlineTables": false,
+    "evenBetterToml.formatter.crlf": false,
+    "evenBetterToml.formatter.indentEntries": false,
+    "evenBetterToml.formatter.indentTables": false,
+}

Cargo.lock

@@ -65,6 +65,12 @@ tokio-stream = { version = "0.1.3", default-features = false, features = [
 toml = { version = "0.8.0", optional = true }
 trybuild-internals-api = { version = "1.0.99", optional = true }
 
+# TODO(mingwei): remove once file locking is stable: https://github.com/rust-lang/rust/issues/130994
+# build.rs `println!("cargo:rustc-cfg=nightly")` doesn't gate this (happens
+# after dependency resolution), but this doesn't hurt to have.
+[target.'cfg(not(nightly))'.dependencies]
+fs2 = "0.4.0"
+
 [target.'cfg(target_os = "linux")'.dependencies]
 chrono = { version = "0.4.39", optional = true }
 procfs = { version = "0.17.0", optional = true }

hydro_lang/Cargo.toml

@@ -265,10 +265,12 @@ pub fn create_trybuild()
     {
         let _concurrent_test_lock = CONCURRENT_TEST_LOCK.lock().unwrap();
 
-        #[cfg(nightly)]
         let project_lock = File::create(path!(project.dir / ".hydro-trybuild-lock"))?;
+        // TODO(mingwei): remove cfg once file locking is stable: https://github.com/rust-lang/rust/issues/130994
         #[cfg(nightly)]
         project_lock.lock()?;
+        #[cfg(not(nightly))]
+        fs2::FileExt::lock_exclusive(&project_lock)?;
 
         let manifest_toml = toml::to_string(&project.manifest)?;
         write_atomic(manifest_toml.as_ref(), &path!(project.dir / "Cargo.toml"))?;
@@ -309,8 +311,12 @@ fn write_atomic(contents: &[u8], path: &Path) -> Result<(), std::io::Error> {
         .create(true)
         .truncate(false)
         .open(path)?;
+
+    // TODO(mingwei): remove cfg once file locking is stable: https://github.com/rust-lang/rust/issues/130994
     #[cfg(nightly)]
     file.lock()?;
+    #[cfg(not(nightly))]
+    fs2::FileExt::lock_exclusive(&file)?;
 
     let mut existing_contents = Vec::new();
     file.read_to_end(&mut existing_contents)?;