Mark functions const where possible

.bazelrc

@@ -54,7 +54,7 @@ build --aspects=@rules_rust//rust:defs.bzl%rustfmt_aspect
 build --aspects=@rules_rust//rust:defs.bzl%rust_clippy_aspect
 
 # TODO(aaronmondal): Extend these flags until we can run with clippy::pedantic.
-build --@rules_rust//:clippy_flags=-Dwarnings,-Dclippy::uninlined_format_args,-Dclippy::manual_string_new,-Dclippy::manual_let_else,-Dclippy::single_match_else,-Dclippy::redundant_closure_for_method_calls,-Dclippy::semicolon_if_nothing_returned,-Dclippy::unreadable_literal,-Dclippy::range_plus_one,-Dclippy::inconsistent_struct_constructor,-Dclippy::match_wildcard_for_single_variants,-Dclippy::implicit_clone,-Dclippy::needless_pass_by_value,-Dclippy::explicit_deref_methods,-Dclippy::trivially_copy_pass_by_ref,-Dclippy::unnecessary_wraps,-Dclippy::cast_lossless,-Dclippy::map_unwrap_or,-Dclippy::ref_as_ptr,-Dclippy::inline_always,-Dclippy::redundant_else,-Dclippy::return_self_not_must_use,-Dclippy::match_same_arms,-Dclippy::explicit_iter_loop,-Dclippy::items_after_statements,-Dclippy::explicit_into_iter_loop,-Dclippy::stable_sort_primitive,-Dclippy::ptr_as_ptr,-Dclippy::needless_raw_string_hashes,-Dclippy::default_trait_access,-Dclippy::ignored_unit_patterns,-Dclippy::needless_continue,-Dclippy::wildcard_imports,-Dclippy::doc_markdown,-Dclippy::struct_field_names,-Dclippy::implicit_hasher
+build --@rules_rust//:clippy_flags=-Dwarnings,-Dclippy::missing_const_for_fn,-Dclippy::uninlined_format_args,-Dclippy::manual_string_new,-Dclippy::manual_let_else,-Dclippy::single_match_else,-Dclippy::redundant_closure_for_method_calls,-Dclippy::semicolon_if_nothing_returned,-Dclippy::unreadable_literal,-Dclippy::range_plus_one,-Dclippy::inconsistent_struct_constructor,-Dclippy::match_wildcard_for_single_variants,-Dclippy::implicit_clone,-Dclippy::needless_pass_by_value,-Dclippy::explicit_deref_methods,-Dclippy::trivially_copy_pass_by_ref,-Dclippy::unnecessary_wraps,-Dclippy::cast_lossless,-Dclippy::map_unwrap_or,-Dclippy::ref_as_ptr,-Dclippy::inline_always,-Dclippy::redundant_else,-Dclippy::return_self_not_must_use,-Dclippy::match_same_arms,-Dclippy::explicit_iter_loop,-Dclippy::items_after_statements,-Dclippy::explicit_into_iter_loop,-Dclippy::stable_sort_primitive,-Dclippy::ptr_as_ptr,-Dclippy::needless_raw_string_hashes,-Dclippy::default_trait_access,-Dclippy::ignored_unit_patterns,-Dclippy::needless_continue,-Dclippy::wildcard_imports,-Dclippy::doc_markdown,-Dclippy::struct_field_names,-Dclippy::implicit_hasher
 build --@rules_rust//:clippy.toml=//:clippy.toml
 
 test --@rules_rust//:rustfmt.toml=//:.rustfmt.toml

nativelink-config/src/lib.rs

@@ -72,7 +72,7 @@ struct NamedConfigsVisitor<T> {
 }
 
 impl<T> NamedConfigsVisitor<T> {
-    fn new() -> Self {
+    const fn new() -> Self {
         NamedConfigsVisitor {
             phantom: PhantomData,
         }

nativelink-proto/gen_lib_rs_tool.py

@@ -43,6 +43,7 @@
     clippy::doc_markdown,
     clippy::doc_markdown,
     clippy::large_enum_variant,
+    clippy::missing_const_for_fn,
     rustdoc::invalid_html_tags
 )]
 """

nativelink-proto/genproto/lib.rs

@@ -22,6 +22,7 @@
     clippy::doc_markdown,
     clippy::doc_markdown,
     clippy::large_enum_variant,
+    clippy::missing_const_for_fn,
     rustdoc::invalid_html_tags
 )]
 

nativelink-scheduler/src/awaited_action_db/awaited_action.rs

@@ -113,7 +113,7 @@ impl AwaitedAction {
         }
     }
 
-    pub(crate) fn version(&self) -> u64 {
+    pub(crate) const fn version(&self) -> u64 {
         self.version.0
     }
 
@@ -125,35 +125,35 @@ impl AwaitedAction {
         self.version = AwaitedActionVersion(self.version.0 + 1);
     }
 
-    pub fn action_info(&self) -> &Arc<ActionInfo> {
+    pub const fn action_info(&self) -> &Arc<ActionInfo> {
         &self.action_info
     }
 
-    pub fn operation_id(&self) -> &OperationId {
+    pub const fn operation_id(&self) -> &OperationId {
         &self.operation_id
     }
 
-    pub(crate) fn sort_key(&self) -> AwaitedActionSortKey {
+    pub(crate) const fn sort_key(&self) -> AwaitedActionSortKey {
         self.sort_key
     }
 
-    pub fn state(&self) -> &Arc<ActionState> {
+    pub const fn state(&self) -> &Arc<ActionState> {
         &self.state
     }
 
-    pub(crate) fn worker_id(&self) -> Option<WorkerId> {
+    pub(crate) const fn worker_id(&self) -> Option<WorkerId> {
         self.worker_id
     }
 
-    pub(crate) fn last_worker_updated_timestamp(&self) -> SystemTime {
+    pub(crate) const fn last_worker_updated_timestamp(&self) -> SystemTime {
         self.last_worker_updated_timestamp
     }
 
     pub(crate) fn worker_keep_alive(&mut self, now: SystemTime) {
         self.last_worker_updated_timestamp = now;
     }
 
-    pub(crate) fn last_client_keepalive_timestamp(&self) -> SystemTime {
+    pub(crate) const fn last_client_keepalive_timestamp(&self) -> SystemTime {
         self.last_client_keepalive_timestamp
     }
     pub(crate) fn update_client_keep_alive(&mut self, now: SystemTime) {
@@ -235,7 +235,7 @@ impl AwaitedActionSortKey {
         Self::new(priority, timestamp)
     }
 
-    pub(crate) fn as_u64(self) -> u64 {
+    pub(crate) const fn as_u64(self) -> u64 {
         self.0
     }
 }

nativelink-scheduler/src/memory_awaited_action_db.rs

@@ -57,14 +57,17 @@ struct ClientAwaitedAction {
 }
 
 impl ClientAwaitedAction {
-    pub fn new(operation_id: OperationId, event_tx: mpsc::UnboundedSender<ActionEvent>) -> Self {
+    pub const fn new(
+        operation_id: OperationId,
+        event_tx: mpsc::UnboundedSender<ActionEvent>,
+    ) -> Self {
         Self {
             operation_id,
             event_tx,
         }
     }
 
-    pub fn operation_id(&self) -> &OperationId {
+    pub const fn operation_id(&self) -> &OperationId {
         &self.operation_id
     }
 }

nativelink-scheduler/src/simple_scheduler_state_manager.rs

@@ -77,7 +77,7 @@ where
     I: InstantWrapper,
     NowFn: Fn() -> I + Clone + Send + Unpin + Sync + 'static,
 {
-    fn new(
+    const fn new(
         sub: U,
         simple_scheduler_state_manager: Weak<SimpleSchedulerStateManager<T, I, NowFn>>,
         no_event_action_timeout: Duration,
@@ -134,7 +134,7 @@ where
     I: InstantWrapper,
     NowFn: Fn() -> I + Clone + Send + Unpin + Sync + 'static,
 {
-    fn new(
+    const fn new(
         awaited_action_sub: U,
         simple_scheduler_state_manager: Weak<SimpleSchedulerStateManager<T, I, NowFn>>,
         no_event_action_timeout: Duration,
@@ -630,7 +630,7 @@ where
     where
         F: Fn(T::Subscriber) -> Box<dyn ActionStateResult> + Send + Sync + 'a,
     {
-        fn sorted_awaited_action_state_for_flags(
+        const fn sorted_awaited_action_state_for_flags(
             stage: OperationStageFlags,
         ) -> Option<SortedAwaitedActionState> {
             match stage {

nativelink-scheduler/src/store_awaited_action_db.rs

@@ -70,7 +70,7 @@ where
     I: InstantWrapper,
     NowFn: Fn() -> I,
 {
-    fn new(
+    const fn new(
         maybe_client_operation_id: Option<ClientOperationId>,
         subscription_key: OperationIdToAwaitedAction<'static>,
         weak_store: Weak<S>,
@@ -306,7 +306,7 @@ impl SchedulerStoreDecodeTo for SearchStateToAwaitedAction {
     }
 }
 
-fn get_state_prefix(state: SortedAwaitedActionState) -> &'static str {
+const fn get_state_prefix(state: SortedAwaitedActionState) -> &'static str {
     match state {
         SortedAwaitedActionState::CacheCheck => "cache_check",
         SortedAwaitedActionState::Queued => "queued",

nativelink-scheduler/src/worker.rs

@@ -237,7 +237,7 @@ impl Worker {
         }
     }
 
-    pub fn can_accept_work(&self) -> bool {
+    pub const fn can_accept_work(&self) -> bool {
         !self.is_paused && !self.is_draining
     }
 }

nativelink-scheduler/tests/utils/scheduler_utils.rs

@@ -58,7 +58,7 @@ impl TokioWatchActionStateResult {
     // Note: This function is only used in tests, but for some reason
     // rust doesn't detect it as used.
     #[allow(dead_code)]
-    pub fn new(
+    pub const fn new(
         client_operation_id: OperationId,
         action_info: Arc<ActionInfo>,
         rx: watch::Receiver<Arc<ActionState>>,

nativelink-service/src/execution_server.rs

@@ -53,7 +53,7 @@ struct NativelinkOperationId {
 }
 
 impl NativelinkOperationId {
-    fn new(instance_name: InstanceInfoName, client_operation_id: OperationId) -> Self {
+    const fn new(instance_name: InstanceInfoName, client_operation_id: OperationId) -> Self {
         Self {
             instance_name,
             client_operation_id,

nativelink-service/src/health_server.rs

@@ -40,7 +40,7 @@ pub struct HealthServer {
 }
 
 impl HealthServer {
-    pub fn new(health_registry: HealthRegistry) -> Self {
+    pub const fn new(health_registry: HealthRegistry) -> Self {
         Self { health_registry }
     }
 }

nativelink-service/tests/worker_api_server_test.rs

@@ -133,7 +133,7 @@ struct TestContext {
 }
 
 #[allow(clippy::unnecessary_wraps)]
-fn static_now_fn() -> Result<Duration, Error> {
+const fn static_now_fn() -> Result<Duration, Error> {
     Ok(Duration::from_secs(BASE_NOW_S))
 }
 

nativelink-store/src/compression_store.rs

@@ -146,7 +146,7 @@ pub struct Footer {
 /// `lz4_flex::block::get_maximum_output_size()` way over estimates, so we use the
 /// one provided here: <https://github.com/torvalds/linux/blob/master/include/linux/lz4.h#L61>
 /// Local testing shows this gives quite accurate worst case given random input.
-fn lz4_compress_bound(input_size: u64) -> u64 {
+const fn lz4_compress_bound(input_size: u64) -> u64 {
     input_size + (input_size / 255) + 16
 }
 

nativelink-store/src/fast_slow_store.rs

@@ -62,11 +62,11 @@ impl FastSlowStore {
         })
     }
 
-    pub fn fast_store(&self) -> &Store {
+    pub const fn fast_store(&self) -> &Store {
         &self.fast_store
     }
 
-    pub fn slow_store(&self) -> &Store {
+    pub const fn slow_store(&self) -> &Store {
         &self.slow_store
     }
 

nativelink-util/src/buf_channel.rs

@@ -327,7 +327,7 @@ impl DropCloserReadHalf {
     }
 
     /// The number of bytes received over this stream so far.
-    pub fn get_bytes_received(&self) -> u64 {
+    pub const fn get_bytes_received(&self) -> u64 {
         self.bytes_received
     }
 

nativelink-util/src/chunked_stream.rs

@@ -52,7 +52,7 @@ where
     F: FnMut(Bound<K>, Bound<K>, VecDeque<T>) -> Fut,
     Fut: Future<Output = Result<Option<((Bound<K>, Bound<K>), VecDeque<T>)>, E>>,
 {
-    pub fn new(start_key: Bound<K>, end_key: Bound<K>, chunk_fn: F) -> Self {
+    pub const fn new(start_key: Bound<K>, end_key: Bound<K>, chunk_fn: F) -> Self {
         Self {
             chunk_fn,
             buffer: VecDeque::new(),

nativelink-util/src/fs.rs

@@ -75,7 +75,7 @@ impl ResumeableFileSlot {
         }
     }
 
-    pub fn new_with_take(file: Take<FileSlot>, path: PathBuf, is_write: bool) -> Self {
+    pub const fn new_with_take(file: Take<FileSlot>, path: PathBuf, is_write: bool) -> Self {
         Self {
             maybe_file_slot: MaybeFileSlot::Open(file),
             path,

nativelink-util/src/metrics_utils.rs

@@ -111,7 +111,7 @@ struct DropCounter<'a> {
 
 impl<'a> DropCounter<'a> {
     #[inline]
-    pub fn new(counter: &'a AtomicU64) -> Self {
+    pub const fn new(counter: &'a AtomicU64) -> Self {
         Self { counter }
     }
 }

nativelink-util/src/origin_context.rs

@@ -337,7 +337,7 @@ impl<T> ContextAwareFuture<T> {
 
     #[must_use = "futures do nothing unless you `.await` or poll them"]
     #[inline]
-    pub(crate) fn new(context: Option<Arc<OriginContext>>, inner: Instrumented<T>) -> Self {
+    pub(crate) const fn new(context: Option<Arc<OriginContext>>, inner: Instrumented<T>) -> Self {
         Self {
             inner: ManuallyDrop::new(inner),
             context,

nativelink-util/src/origin_event.rs

@@ -56,7 +56,7 @@ static NODE_ID: OnceLock<[u8; 6]> = OnceLock::new();
 /// meaning you may use the first nibble for other
 /// purposes.
 #[inline]
-pub fn get_id_for_event(event: &Event) -> [u8; 2] {
+pub const fn get_id_for_event(event: &Event) -> [u8; 2] {
     match &event.event {
         None => [0x00, 0x00],
         Some(event::Event::Request(req)) => match req.event {
@@ -122,7 +122,7 @@ pub struct OriginEventCollector {
 }
 
 impl OriginEventCollector {
-    pub fn new(
+    pub const fn new(
         sender: mpsc::Sender<OriginEvent>,
         identity: String,
         bazel_metadata: Option<RequestMetadata>,

nativelink-util/src/origin_event_publisher.rs

@@ -32,7 +32,7 @@ pub struct OriginEventPublisher {
 }
 
 impl OriginEventPublisher {
-    pub fn new(
+    pub const fn new(
         store: Store,
         rx: mpsc::Receiver<OriginEvent>,
         shutdown_tx: broadcast::Sender<ShutdownGuard>,

nativelink-util/src/proto_stream_utils.rs

@@ -79,7 +79,7 @@ where
         futures::future::poll_fn(|cx| Pin::new(&mut *self).poll_next(cx)).await
     }
 
-    pub fn is_first_msg(&self) -> bool {
+    pub const fn is_first_msg(&self) -> bool {
         self.first_msg.is_some()
     }
 }
@@ -152,7 +152,10 @@ pub struct FirstStream {
 }
 
 impl FirstStream {
-    pub fn new(first_response: Option<ReadResponse>, stream: Streaming<ReadResponse>) -> Self {
+    pub const fn new(
+        first_response: Option<ReadResponse>,
+        stream: Streaming<ReadResponse>,
+    ) -> Self {
         Self {
             first_response: Some(first_response),
             stream,
@@ -200,7 +203,7 @@ where
     T: Stream<Item = Result<WriteRequest, E>> + Unpin + Send + 'static,
     E: Into<Error> + 'static,
 {
-    pub fn new(instance_name: String, read_stream: WriteRequestStreamWrapper<T>) -> Self {
+    pub const fn new(instance_name: String, read_stream: WriteRequestStreamWrapper<T>) -> Self {
         Self {
             instance_name,
             read_stream_error: None,
@@ -231,7 +234,7 @@ where
         }
     }
 
-    pub fn can_resume(&self) -> bool {
+    pub const fn can_resume(&self) -> bool {
         self.read_stream_error.is_none()
             && (self.cached_messages[0].is_some() || self.read_stream.is_first_msg())
     }
@@ -261,7 +264,7 @@ where
     T: Stream<Item = Result<WriteRequest, E>> + Unpin + Send + 'static,
     E: Into<Error> + 'static,
 {
-    pub fn new(shared_state: Arc<Mutex<WriteState<T, E>>>) -> Self {
+    pub const fn new(shared_state: Arc<Mutex<WriteState<T, E>>>) -> Self {
         Self { shared_state }
     }
 }

nativelink-util/src/retry.rs

@@ -27,7 +27,7 @@ struct ExponentialBackoff {
 }
 
 impl ExponentialBackoff {
-    fn new(base: Duration) -> Self {
+    const fn new(base: Duration) -> Self {
         ExponentialBackoff { current: base }
     }
 }
@@ -59,7 +59,7 @@ pub struct Retrier {
     config: Retry,
 }
 
-fn to_error_code(code: Code) -> ErrorCode {
+const fn to_error_code(code: Code) -> ErrorCode {
     match code {
         Code::Cancelled => ErrorCode::Cancelled,
         Code::InvalidArgument => ErrorCode::InvalidArgument,

nativelink-util/src/task.rs

@@ -109,7 +109,7 @@ pub struct JoinHandleDropGuard<T> {
 }
 
 impl<T> JoinHandleDropGuard<T> {
-    pub fn new(inner: JoinHandle<T>) -> Self {
+    pub const fn new(inner: JoinHandle<T>) -> Self {
         Self { inner }
     }
 }