refactor: Replace OnceCell with std::sync::OnceLock

opentelemetry-prometheus/examples/hyper.rs

@@ -7,6 +7,7 @@ use hyper::{
 };
 use hyper_util::rt::{TokioExecutor, TokioIo};
 use once_cell::sync::Lazy;
+use opentelemetry::time::now;
 use opentelemetry::{
     metrics::{Counter, Histogram, MeterProvider as _},
     KeyValue,
@@ -15,7 +16,6 @@ use opentelemetry_sdk::metrics::SdkMeterProvider;
 use prometheus::{Encoder, Registry, TextEncoder};
 use std::net::SocketAddr;
 use std::sync::Arc;
-use opentelemetry::time::now;
 use tokio::net::TcpListener;
 
 static HANDLER_ALL: Lazy<[KeyValue; 1]> = Lazy::new(|| [KeyValue::new("handler", "all")]);

opentelemetry-prometheus/src/config.rs

@@ -1,7 +1,6 @@
 use core::fmt;
-use once_cell::sync::OnceCell;
 use opentelemetry_sdk::metrics::{ManualReaderBuilder, MetricError, MetricResult};
-use std::sync::{Arc, Mutex};
+use std::sync::{Arc, Mutex, OnceLock};
 
 use crate::{Collector, PrometheusExporter, ResourceSelector};
 
@@ -124,11 +123,11 @@ impl ExporterBuilder {
             without_units: self.without_units,
             without_counter_suffixes: self.without_counter_suffixes,
             disable_scope_info: self.disable_scope_info,
-            create_target_info_once: OnceCell::new(),
+            create_target_info_once: OnceLock::new(),
             namespace: self.namespace,
             inner: Mutex::new(Default::default()),
             resource_selector: self.resource_selector,
-            resource_labels_once: OnceCell::new(),
+            resource_labels_once: OnceLock::new(),
         };
 
         let registry = self.registry.unwrap_or_default();

opentelemetry-prometheus/src/lib.rs

@@ -106,7 +106,7 @@
 )]
 #![cfg_attr(test, deny(warnings))]
 
-use once_cell::sync::{Lazy, OnceCell};
+use once_cell::sync::Lazy;
 use opentelemetry::{otel_error, otel_warn, InstrumentationScope, Key, Value};
 use opentelemetry_sdk::{
     error::OTelSdkResult,
@@ -125,7 +125,7 @@ use std::{
     any::TypeId,
     borrow::Cow,
     collections::{BTreeMap, HashMap},
-    sync::{Arc, Mutex},
+    sync::{Arc, Mutex, OnceLock},
 };
 use std::{fmt, sync::Weak};
 
@@ -189,8 +189,8 @@ struct Collector {
     without_units: bool,
     without_counter_suffixes: bool,
     disable_scope_info: bool,
-    create_target_info_once: OnceCell<MetricFamily>,
-    resource_labels_once: OnceCell<Vec<LabelPair>>,
+    create_target_info_once: OnceLock<MetricFamily>,
+    resource_labels_once: OnceLock<Vec<LabelPair>>,
     namespace: Option<String>,
     inner: Mutex<CollectorInner>,
     resource_selector: ResourceSelector,