tower-util: reduce dependencies, make call-all optional

tower-util/Cargo.toml

@@ -22,14 +22,20 @@ Utilities for working with `Service`.
 categories = ["asynchronous", "network-programming"]
 edition = "2018"
 
+[features]
+call-all = ["futures-util"]
+
 [dependencies]
 tower-service = "0.3"
 pin-project = "0.4"
-futures-util = "0.3"
-futures-core = "0.3"
+futures-core = { version = "0.3", default-features = false }
+
+# Optional
+
+futures-util = { version = "0.3", optional = true, default-features = false }
 
 [dev-dependencies]
 tokio-test = "0.2"
-tokio = { version = "0.2", features = ["stream", "sync", "macros"] } 
+tokio = { version = "0.2", features = ["stream", "sync", "macros"] }
 tower = { version = "0.3", path = "../tower" }
 tower-test = { version = "0.3", path = "../tower-test" }

tower-util/src/either.rs

@@ -2,7 +2,7 @@
 //!
 //! See `Either` documentation for more details.
 
-use futures_util::ready;
+use futures_core::ready;
 use pin_project::{pin_project, project};
 use std::{
     future::Future,

tower-util/src/lib.rs

@@ -10,6 +10,7 @@
 //! Various utility types and functions that are generally with Tower.
 
 mod boxed;
+#[cfg(feature = "call-all")]
 mod call_all;
 mod either;
 mod oneshot;
@@ -20,7 +21,6 @@ mod service_fn;
 
 pub use crate::{
     boxed::{BoxService, UnsyncBoxService},
-    call_all::{CallAll, CallAllUnordered},
     either::Either,
     oneshot::Oneshot,
     optional::Optional,
@@ -28,6 +28,9 @@ pub use crate::{
     service_fn::{service_fn, ServiceFn},
 };
 
+#[cfg(feature = "call-all")]
+pub use crate::call_all::{CallAll, CallAllUnordered};
+
 pub mod error {
     //! Error types
 

tower-util/src/oneshot.rs

@@ -1,4 +1,4 @@
-use futures_util::ready;
+use futures_core::ready;
 use pin_project::{pin_project, project};
 use std::{
     fmt,

tower-util/src/optional/future.rs

@@ -1,5 +1,5 @@
 use super::{error, Error};
-use futures_util::ready;
+use futures_core::ready;
 use pin_project::pin_project;
 use std::{
     future::Future,

tower-util/src/ready.rs

@@ -1,6 +1,6 @@
 use std::{fmt, marker::PhantomData};
 
-use futures_util::ready;
+use futures_core::ready;
 use std::{
     future::Future,
     pin::Pin,

tower/Cargo.toml

@@ -36,7 +36,7 @@ tower-load-shed = { version = "0.3", path = "../tower-load-shed" }
 tower-retry = { version = "0.3", path = "../tower-retry" }
 tower-service = "0.3"
 tower-timeout = { version = "0.3", path = "../tower-timeout" }
-tower-util = { version = "0.3", path = "../tower-util" }
+tower-util = { version = "0.3", path = "../tower-util", features = ["call-all"] }
 futures-core = "0.3"
 
 [dev-dependencies]