bb8: Make parking_lot an optional feature enabled by default

bb8/Cargo.toml

@@ -13,8 +13,12 @@ rust-version = "1.60"
 async-trait = "0.1"
 futures-channel = "0.3.2"
 futures-util = { version = "0.3.2", default-features = false, features = ["channel"] }
-parking_lot = "0.12"
-tokio = { version = "1.0", features = ["rt", "time", "parking_lot"] }
+parking_lot = { version = "0.12", optional = true }
+tokio = { version = "1.0", features = ["rt", "time"] }
 
 [dev-dependencies]
 tokio = { version = "1.0", features = ["macros"] }
+
+[features]
+parking_lot = ["dep:parking_lot", "tokio/parking_lot"]
+default = ["parking_lot"]

bb8/src/internals.rs

@@ -2,8 +2,8 @@ use std::cmp::min;
 use std::sync::Arc;
 use std::time::Instant;
 
+use crate::lock::Mutex;
 use futures_channel::oneshot;
-use parking_lot::Mutex;
 
 use crate::api::{Builder, ManageConnection};
 use std::collections::VecDeque;

bb8/src/lib.rs

@@ -41,3 +41,33 @@ pub use api::{
 
 mod inner;
 mod internals;
+mod lock {
+    #[cfg(feature = "parking_lot")]
+    use parking_lot::Mutex as MutexImpl;
+    #[cfg(feature = "parking_lot")]
+    use parking_lot::MutexGuard;
+
+    #[cfg(not(feature = "parking_lot"))]
+    use std::sync::Mutex as MutexImpl;
+    #[cfg(not(feature = "parking_lot"))]
+    use std::sync::MutexGuard;
+
+    pub(crate) struct Mutex<T>(MutexImpl<T>);
+
+    impl<T> Mutex<T> {
+        pub(crate) fn new(val: T) -> Self {
+            Self(MutexImpl::new(val))
+        }
+
+        pub(crate) fn lock(&self) -> MutexGuard<'_, T> {
+            #[cfg(feature = "parking_lot")]
+            {
+                self.0.lock()
+            }
+            #[cfg(not(feature = "parking_lot"))]
+            {
+                self.0.lock().unwrap()
+            }
+        }
+    }
+}