futures: support std::futures::Future with !Unpin futures

- Thank you Eliza Weisman (hawkw) for the solution using the pin-utils crate
- Added feature gates for the futures 0.1, tokio, and std::future implementations

tracing-futures/Cargo.toml

@@ -5,10 +5,13 @@ authors = ["Eliza Weisman <eliza@buoyant.io>"]
 edition = "2018"
 
 [features]
-default = ["tokio"]
+default = ["futures-01", "tokio"]
+futures-01 = ["futures"]
+std-future = ["pin-utils"]
 
 [dependencies]
-futures = "0.1"
+futures = { version = "0.1", optional = true }
+pin-utils = { version = "0.1.0-alpha.4", optional = true }
 tracing = "0.1"
 tokio = { version = "0.1", optional = true }
 tokio-executor = { version = "0.1", optional = true }

tracing-futures/src/executor.rs

@@ -1,15 +1,14 @@
 use crate::{Instrument, Instrumented, WithDispatch};
+#[cfg(feature = "futures-01")]
 use futures::{
-    future::{ExecuteError, Executor},
-    Future,
-};
-
-#[cfg(feature = "tokio")]
-use tokio::{
-    executor::{Executor as TokioExecutor, SpawnError},
-    runtime::{current_thread, Runtime, TaskExecutor},
+  future::{ExecuteError, Executor},
+  Future,
 };
+#[cfg(feature = "futures-01")]
+use tokio::executor::{Executor as TokioExecutor, SpawnError};
+use tokio::runtime::{current_thread, Runtime, TaskExecutor};
 
+#[cfg(feature = "futures-01")]
 macro_rules! deinstrument_err {
     ($e:expr) => {
         $e.map_err(|e| {
@@ -20,6 +19,7 @@ macro_rules! deinstrument_err {
     };
 }
 
+#[cfg(feature = "futures-01")]
 impl<T, F> Executor<F> for Instrumented<T>
 where
     T: Executor<Instrumented<F>>,
@@ -31,7 +31,7 @@ where
     }
 }
 
-#[cfg(feature = "tokio")]
+#[cfg(all(feature = "futures-01", feature = "tokio"))]
 impl<T> TokioExecutor for Instrumented<T>
 where
     T: TokioExecutor,
@@ -56,6 +56,7 @@ impl Instrumented<Runtime> {
     ///
     /// This method simply wraps a call to `tokio::runtime::Runtime::spawn`,
     /// instrumenting the spawned future beforehand.
+    #[cfg(feature = "futures-01")]
     pub fn spawn<F>(&mut self, future: F) -> &mut Self
     where
         F: Future<Item = (), Error = ()> + Send + 'static,
@@ -80,6 +81,7 @@ impl Instrumented<Runtime> {
     ///
     /// This function panics if the executor is at capacity, if the provided
     /// future panics, or if called within an asynchronous execution context.
+    #[cfg(feature = "futures-01")]
     pub fn block_on<F, R, E>(&mut self, future: F) -> Result<R, E>
     where
         F: Send + 'static + Future<Item = R, Error = E>,
@@ -108,6 +110,7 @@ impl Instrumented<current_thread::Runtime> {
     ///
     /// This method simply wraps a call to `current_thread::Runtime::spawn`,
     /// instrumenting the spawned future beforehand.
+    #[cfg(feature = "futures-01")]
     pub fn spawn<F>(&mut self, future: F) -> &mut Self
     where
         F: Future<Item = (), Error = ()> + 'static,
@@ -141,6 +144,7 @@ impl Instrumented<current_thread::Runtime> {
     ///
     /// This function panics if the executor is at capacity, if the provided
     /// future panics, or if called within an asynchronous execution context.
+    #[cfg(feature = "futures-01")]
     pub fn block_on<F, R, E>(&mut self, future: F) -> Result<R, E>
     where
         F: 'static + Future<Item = R, Error = E>,
@@ -165,6 +169,7 @@ impl Instrumented<current_thread::Runtime> {
     }
 }
 
+#[cfg(feature = "futures-01")]
 impl<T, F> Executor<F> for WithDispatch<T>
 where
     T: Executor<WithDispatch<F>>,
@@ -176,7 +181,7 @@ where
     }
 }
 
-#[cfg(feature = "tokio")]
+#[cfg(all(feature = "futures-01", feature = "tokio"))]
 impl<T> TokioExecutor for WithDispatch<T>
 where
     T: TokioExecutor,
@@ -202,6 +207,7 @@ impl WithDispatch<Runtime> {
     ///
     /// This method simply wraps a call to `tokio::runtime::Runtime::spawn`,
     /// instrumenting the spawned future beforehand.
+    #[cfg(feature = "futures-01")]
     pub fn spawn<F>(&mut self, future: F) -> &mut Self
     where
         F: Future<Item = (), Error = ()> + Send + 'static,
@@ -227,6 +233,7 @@ impl WithDispatch<Runtime> {
     ///
     /// This function panics if the executor is at capacity, if the provided
     /// future panics, or if called within an asynchronous execution context.
+    #[cfg(feature = "futures-01")]
     pub fn block_on<F, R, E>(&mut self, future: F) -> Result<R, E>
     where
         F: Send + 'static + Future<Item = R, Error = E>,
@@ -257,6 +264,7 @@ impl WithDispatch<current_thread::Runtime> {
     ///
     /// This method simply wraps a call to `current_thread::Runtime::spawn`,
     /// instrumenting the spawned future beforehand.
+    #[cfg(feature = "futures-01")]
     pub fn spawn<F>(&mut self, future: F) -> &mut Self
     where
         F: Future<Item = (), Error = ()> + 'static,
@@ -290,6 +298,7 @@ impl WithDispatch<current_thread::Runtime> {
     ///
     /// This function panics if the executor is at capacity, if the provided
     /// future panics, or if called within an asynchronous execution context.
+    #[cfg(feature = "futures-01")]
     pub fn block_on<F, R, E>(&mut self, future: F) -> Result<R, E>
     where
         F: 'static + Future<Item = R, Error = E>,

tracing-futures/src/lib.rs

@@ -14,33 +14,37 @@
 //!
 //! [`Instrument`]: trait.Instrument.html
 //! [`WithSubscriber`]: trait.WithSubscriber.html
+#[cfg(feature = "futures-01")]
 extern crate futures;
+#[cfg(feature = "std-future")]
+extern crate pin_utils;
 #[cfg(feature = "tokio")]
 extern crate tokio;
 #[cfg(feature = "tokio-executor")]
 extern crate tokio_executor;
 #[cfg_attr(test, macro_use)]
 extern crate tracing;
 
+#[cfg(feature = "std-future")]
 use std::{
   pin::Pin,
   task::Context,
 };
 
+#[cfg(feature = "futures-01")]
 use futures::{Sink, StartSend, Stream};
-use tracing::{dispatcher, Dispatch, Span};
+#[cfg(feature = "futures-01")]
+use tracing::dispatcher;
+use tracing::{Dispatch, Span};
 
+#[cfg(feature = "tokio")]
 pub mod executor;
 
 // TODO: seal?
 pub trait Instrument: Sized {
     fn instrument(self, span: Span) -> Instrumented<Self> {
         Instrumented { inner: self, span }
     }
-
-    fn boxed_instrument(self, span: Span) -> Instrumented<Pin<Box<Self>>> {
-        Instrumented { inner: Box::pin(self), span }
-    }
 }
 
 pub trait WithSubscriber: Sized {
@@ -69,16 +73,26 @@ pub struct WithDispatch<T> {
 
 impl<T: Sized> Instrument for T {}
 
-impl<P: std::future::Future + Unpin> std::future::Future for Instrumented<P> {
-    type Output = P::Output;
+#[cfg(feature = "std-future")]
+impl<T: std::future::Future> Instrumented<T> {
+    pin_utils::unsafe_pinned!(inner: T);
+}
 
-    fn poll(self: Pin<&mut Self>, lw: &mut Context) -> std::task::Poll<Self::Output> {
-        let this = self.get_mut();
-        let _enter = this.span.enter();
-        Pin::new(&mut this.inner).poll(lw)
+#[cfg(feature = "std-future")]
+impl<T: std::future::Future> std::future::Future for Instrumented<T> {
+    type Output = T::Output;
+
+    fn poll(mut self: Pin<&mut Self>, lw: &mut Context) -> std::task::Poll<Self::Output> {
+        let span = self.as_ref().span.clone();
+        let _enter = span.enter();
+        self.as_mut().inner().poll(lw)
     }
 }
 
+#[cfg(feature = "std-future")]
+impl<T: Unpin> Unpin for Instrumented<T> {}
+
+#[cfg(feature = "futures-01")]
 impl<T: futures::Future> futures::Future for Instrumented<T> {
     type Item = T::Item;
     type Error = T::Error;
@@ -89,6 +103,7 @@ impl<T: futures::Future> futures::Future for Instrumented<T> {
     }
 }
 
+#[cfg(feature = "futures-01")]
 impl<T: Stream> Stream for Instrumented<T> {
     type Item = T::Item;
     type Error = T::Error;
@@ -99,6 +114,7 @@ impl<T: Stream> Stream for Instrumented<T> {
     }
 }
 
+#[cfg(feature = "futures-01")]
 impl<T: Sink> Sink for Instrumented<T> {
     type SinkItem = T::SinkItem;
     type SinkError = T::SinkError;
@@ -135,6 +151,7 @@ impl<T> Instrumented<T> {
 
 impl<T: Sized> WithSubscriber for T {}
 
+#[cfg(feature = "futures-01")]
 impl<T: futures::Future> futures::Future for WithDispatch<T> {
     type Item = T::Item;
     type Error = T::Error;
@@ -146,6 +163,7 @@ impl<T: futures::Future> futures::Future for WithDispatch<T> {
 }
 
 impl<T> WithDispatch<T> {
+    #[cfg(feature = "tokio")]
     pub(crate) fn with_dispatch<U: Sized>(&self, inner: U) -> WithDispatch<U> {
         WithDispatch {
             dispatch: self.dispatch.clone(),
@@ -176,6 +194,8 @@ mod tests {
     extern crate tokio;
 
     use super::{test_support::*, *};
+
+    #[cfg(feature = "futures-01")]
     use futures::{future, stream, task, Async, Future};
     use tracing::{subscriber::with_default, Level};
 
@@ -185,6 +205,7 @@ mod tests {
         polls: usize,
     }
 
+    #[cfg(feature = "futures-01")]
     impl<T, E> futures::Future for PollN<T, E> {
         type Item = T;
         type Error = E;
@@ -220,6 +241,7 @@ mod tests {
         }
     }
 
+    #[cfg(feature = "futures-01")]
     #[test]
     fn future_enter_exit_is_reasonable() {
         let (subscriber, handle) = subscriber::mock()
@@ -239,6 +261,7 @@ mod tests {
         handle.assert_finished();
     }
 
+    #[cfg(feature = "futures-01")]
     #[test]
     fn future_error_ends_span() {
         let (subscriber, handle) = subscriber::mock()
@@ -259,6 +282,7 @@ mod tests {
         handle.assert_finished();
     }
 
+    #[cfg(feature = "futures-01")]
     #[test]
     fn stream_enter_exit_is_reasonable() {
         let (subscriber, handle) = subscriber::mock()
@@ -282,6 +306,7 @@ mod tests {
         handle.assert_finished();
     }
 
+    #[cfg(feature = "futures-01")]
     #[test]
     fn span_follows_future_onto_threadpool() {
         let (subscriber, handle) = subscriber::mock()