Tune up lints for 1.81 Rust

- bump up MSRV to 1.81

.github/workflows/ci.yml

@@ -73,7 +73,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        msrv: ["1.72.0"]
+        msrv: ["1.81.0"]
         os: ["ubuntu", "macOS", "windows"]
     runs-on: ${{ matrix.os }}-latest
     steps:

CHANGELOG.md

@@ -6,6 +6,20 @@ All user visible changes to this project will be documented in this file. This p
 
 
 
+## [0.8.0] · 2024-??-?? (unreleased)
+[0.8.0]: /../../tree/v0.8.0
+
+[Diff](/../../compare/v0.7.0...v0.8.0)
+
+### BC Breaks
+
+- Bumped up [MSRV] to 1.81 because for `#[expect]` attribute usage. ([todo])
+
+[todo]: /../../commit/todo
+
+
+
+
 ## [0.7.0] · 2024-05-30
 [0.7.0]: /../../tree/v0.7.0
 

Cargo.toml

@@ -2,7 +2,7 @@
 name = "metrics-prometheus"
 version = "0.7.0"
 edition = "2021"
-rust-version = "1.72"
+rust-version = "1.81"
 description = "`prometheus` backend for `metrics` crate."
 authors = ["Instrumentisto Team <developer@instrumentisto.com>"]
 license = "MIT OR Apache-2.0"

README.md

@@ -4,7 +4,7 @@
 =================================
 
 [![crates.io](https://img.shields.io/crates/v/metrics-prometheus.svg "crates.io")](https://crates.io/crates/metrics-prometheus)
-[![Rust 1.72+](https://img.shields.io/badge/rustc-1.72+-lightgray.svg "Rust 1.72+")](https://blog.rust-lang.org/2023/08/24/Rust-1.72.0.html)
+[![Rust 1.81+](https://img.shields.io/badge/rustc-1.81+-lightgray.svg "Rust 1.81+")](https://blog.rust-lang.org/2024/09/05/Rust-1.81.0.html)
 [![Unsafe Forbidden](https://img.shields.io/badge/unsafe-forbidden-success.svg "Unsafe forbidden")](https://github.com/rust-secure-code/safety-dance)  
 [![CI](https://github.com/instrumentisto/metrics-prometheus-rs/workflows/CI/badge.svg?branch=main "CI")](https://github.com/instrumentisto/metrics-prometheus-rs/actions?query=workflow%3ACI+branch%3Amain)
 [![Rust docs](https://docs.rs/metrics-prometheus/badge.svg "Rust docs")](https://docs.rs/metrics-prometheus)

src/lib.rs

@@ -51,10 +51,13 @@
 #![forbid(non_ascii_idents, unsafe_code)]
 #![warn(
     clippy::absolute_paths,
+    clippy::allow_attributes,
+    clippy::allow_attributes_without_reason,
     clippy::as_conversions,
     clippy::as_ptr_cast_mut,
     clippy::assertions_on_result_states,
     clippy::branches_sharing_code,
+    clippy::cfg_not_test,
     clippy::clear_with_drain,
     clippy::clone_on_ref_ptr,
     clippy::collection_is_never_read,
@@ -125,6 +128,7 @@
     clippy::rest_pat_in_fully_bound_structs,
     clippy::same_name_method,
     clippy::semicolon_inside_block,
+    clippy::set_contains_or_insert,
     clippy::shadow_unrelated,
     clippy::significant_drop_in_scrutinee,
     clippy::significant_drop_tightening,
@@ -236,9 +240,11 @@ pub fn try_install_freezable(
 ///
 /// If the [`Recorder`] fails to be installed with the
 /// [`metrics::set_global_recorder()`].
-// We do intentionally omit `#[must_use]` here, as we don't want to force
-// library users using the returned `Recorder` directly.
-#[allow(clippy::must_use_candidate)] // intentional
+#[expect( // intentional
+    clippy::must_use_candidate,
+    reason = "`#[must_use]` is omitted here, to avoid forcing library users \
+              using the returned `Recorder` directly"
+)]
 pub fn install() -> Recorder {
     Recorder::builder().build_and_install()
 }
@@ -251,9 +257,11 @@ pub fn install() -> Recorder {
 ///
 /// If the [`FreezableRecorder`] fails to be installed with the
 /// [`metrics::set_global_recorder()`].
-// We do intentionally omit `#[must_use]` here, as we don't want to force
-// library users using the returned `FreezableRecorder` directly.
-#[allow(clippy::must_use_candidate)] // intentional
+#[expect( // intentional
+    clippy::must_use_candidate,
+    reason = "`#[must_use]` is omitted here, to avoid forcing library users \
+              using the returned `Recorder` directly"
+)]
 pub fn install_freezable() -> FreezableRecorder {
     Recorder::builder().build_freezable_and_install()
 }

src/recorder/layer.rs

@@ -14,7 +14,7 @@ pub struct Identity;
 impl<R> Layer<R> for Identity {
     type Output = R;
 
-    #[allow(clippy::renamed_function_params)] // impl related
+    #[expect(clippy::renamed_function_params, reason = "impl related")]
     fn layer(&self, itself: R) -> R {
         itself
     }

src/recorder/mod.rs

@@ -557,9 +557,11 @@ impl<S, L> Builder<S, L> {
     /// );
     /// # Ok::<_, prometheus::Error>(())
     /// ```
-    // TODO: Anonymous lifetimes in `impl Trait` are unstable.
-    //       Try remove on Rust 1.81 upgrade.
-    #[allow(single_use_lifetimes)]
+    // TODO: Try remove on Rust 1.82 upgrade.
+    #[expect( // anonymous lifetimes in `impl Trait` are unstable
+        single_use_lifetimes,
+        reason = "anonymous lifetimes in `impl Trait` are unstable"
+    )]
     pub fn with_registry<'r>(
         mut self,
         registry: impl IntoCow<'r, prometheus::Registry>,

src/storage/immutable.rs

@@ -125,19 +125,22 @@ impl Storage {
     }
 }
 
-// PANIC: `RwLock` usage is fully panic-safe inside, so the `impl` is
-//        infallible, in fact.
-#[allow(clippy::fallible_impl_from)] // intentional
+#[expect( // intentional
+    clippy::fallible_impl_from,
+    reason = "`RwLock` usage is fully panic-safe inside, so the `impl` is \
+              infallible, in fact"
+)]
 impl From<&super::mutable::Storage> for Storage {
     /// Creates a new immutable [`Storage`] by [draining] the referred
     /// [`mutable::Storage`] and leaving it empty.
     ///
     /// [`mutable::Storage`]: super::mutable::Storage
     /// [draining]: HashMap::drain
+    #[expect( // intentional
+        clippy::unwrap_used,
+        reason = "`RwLock` usage is fully panic-safe here"
+    )]
     fn from(mutable: &super::mutable::Storage) -> Self {
-        // PANIC: `RwLock` usage is fully panic-safe here.
-        #![allow(clippy::unwrap_used)] // intentional
-
         Self {
             counters: mutable
                 .counters

src/storage/mutable.rs

@@ -107,21 +107,17 @@ impl Storage {
     /// [`metrics::Recorder::describe_histogram()`] implementations.
     ///
     /// [`help` description]: prometheus::proto::MetricFamily::get_help
+    #[expect( // intentional
+        clippy::missing_panics_doc,
+        clippy::unwrap_used,
+        reason = "`RwLock` usage is fully panic-safe here"
+    )]
     pub fn describe<M>(&self, name: &str, description: String)
     where
         M: metric::Bundled,
         <M as metric::Bundled>::Bundle: Clone,
         Self: super::Get<Collection<<M as metric::Bundled>::Bundle>>,
     {
-        // PANIC: `RwLock` usage is fully panic-safe here.
-        #![allow( // intentional
-            clippy::missing_panics_doc,
-            clippy::unwrap_in_result,
-            clippy::unwrap_used
-        )]
-        // Intentionally, see the comment below on a `write_storage`.
-        #![allow(clippy::significant_drop_tightening)] // intentional
-
         use super::Get as _;
 
         let read_storage = self.collection().read().unwrap();
@@ -158,6 +154,17 @@ impl Storage {
     ///
     /// [`metrics::Registry`]: metrics_util::registry::Registry
     /// [`metrics::registry::Storage`]: metrics_util::registry::Storage
+    #[expect( // intentional
+        clippy::unwrap_in_result,
+        clippy::unwrap_used,
+        reason = "`RwLock` usage is fully panic-safe here (considering the \
+                  `prometheus::Registry::register()` does not)"
+    )]
+    #[expect( // intentional
+        clippy::significant_drop_tightening,
+        reason = "write lock on `storage` is intentionally held till the end \
+                  of the scope, to perform all the operations atomically"
+    )]
     fn register<'k, M>(
         &self,
         key: &'k metrics::Key,
@@ -171,16 +178,6 @@ impl Storage {
             + 'static,
         Self: super::Get<Collection<<M as metric::Bundled>::Bundle>>,
     {
-        // PANIC: `RwLock` usage is panic-safe here (considering the
-        //        `prometheus::Registry::register()` does not).
-        #![allow( // intentional
-            clippy::missing_panics_doc,
-            clippy::unwrap_in_result,
-            clippy::unwrap_used
-        )]
-        // Intentionally, see the comment below on a `storage`.
-        #![allow(clippy::significant_drop_tightening)] // intentional
-
         use super::Get as _;
         use metric::Bundle as _;
 
@@ -241,23 +238,26 @@ impl Storage {
     /// provided `metric`.
     ///
     /// [`metrics::registry::Storage`]: metrics_util::registry::Storage
+    #[expect( // intentional
+        clippy::missing_panics_doc,
+        clippy::unwrap_in_result,
+        clippy::unwrap_used,
+        reason = "`RwLock` usage is fully panic-safe here (considering the \
+                  `prometheus::Registry::register()` does not)"
+    )]
+    #[expect( // intentional
+        clippy::significant_drop_tightening,
+        reason = "write lock on `storage` is intentionally held till the end \
+                  of the scope, to perform the registration in \
+                  `prometheus::Registry` exclusively"
+    )]
     pub fn register_external<M>(&self, metric: M) -> prometheus::Result<()>
     where
         M: metric::Bundled + prometheus::core::Collector,
         <M as metric::Bundled>::Bundle:
             prometheus::core::Collector + Clone + 'static,
         Self: super::Get<Collection<<M as metric::Bundled>::Bundle>>,
     {
-        // PANIC: `RwLock` usage is panic-safe here (considering the
-        //        `prometheus::Registry::register()` does not).
-        #![allow(  // intentional
-            clippy::missing_panics_doc,
-            clippy::unwrap_in_result,
-            clippy::unwrap_used
-        )]
-        // Intentionally, see the comment below on a `storage`.
-        #![allow(clippy::significant_drop_tightening)] // intentional
-
         use super::Get as _;
 
         let name = metric