Merge pull request #506 from stjepang/cleanup-stream

Cleanup stream module

Author: yoshuawuyts

src/io/mod.rs

@@ -19,8 +19,8 @@
 //! [`File`]s:
 //!
 //! ```no_run
-//! use async_std::prelude::*;
 //! use async_std::fs::File;
+//! use async_std::prelude::*;
 //!
 //! # fn main() -> std::io::Result<()> { async_std::task::block_on(async {
 //! #
@@ -47,9 +47,9 @@
 //! coming from:
 //!
 //! ```no_run
-//! use async_std::io::prelude::*;
-//! use async_std::io::SeekFrom;
 //! use async_std::fs::File;
+//! use async_std::io::SeekFrom;
+//! use async_std::prelude::*;
 //!
 //! # fn main() -> std::io::Result<()> { async_std::task::block_on(async {
 //! #
@@ -82,9 +82,9 @@
 //! methods to any reader:
 //!
 //! ```no_run
-//! use async_std::io::prelude::*;
-//! use async_std::io::BufReader;
 //! use async_std::fs::File;
+//! use async_std::io::BufReader;
+//! use async_std::prelude::*;
 //!
 //! # fn main() -> std::io::Result<()> { async_std::task::block_on(async {
 //! #
@@ -104,9 +104,9 @@
 //! to [`write`][`Write::write`]:
 //!
 //! ```no_run
-//! use async_std::io::prelude::*;
-//! use async_std::io::BufWriter;
 //! use async_std::fs::File;
+//! use async_std::io::BufWriter;
+//! use async_std::io::prelude::*;
 //!
 //! # fn main() -> std::io::Result<()> { async_std::task::block_on(async {
 //! #
@@ -179,9 +179,9 @@
 //! lines:
 //!
 //! ```no_run
-//! use async_std::prelude::*;
-//! use async_std::io::BufReader;
 //! use async_std::fs::File;
+//! use async_std::io::BufReader;
+//! use async_std::prelude::*;
 //!
 //! # fn main() -> std::io::Result<()> { async_std::task::block_on(async {
 //! #

src/stream/extend.rs

@@ -65,10 +65,10 @@ pub trait Extend<A> {
 /// ```
 #[cfg(feature = "unstable")]
 #[cfg_attr(feature = "docs", doc(cfg(unstable)))]
-pub async fn extend<'a, C, A, T>(collection: &mut C, stream: T)
+pub async fn extend<'a, C, T, S>(collection: &mut C, stream: S)
 where
-    C: Extend<A>,
-    T: IntoStream<Item = A> + 'a,
+    C: Extend<T>,
+    S: IntoStream<Item = T> + 'a,
 {
     Extend::extend(collection, stream).await
 }

src/stream/from_fn.rs

@@ -1,28 +1,21 @@
-use std::marker::PhantomData;
 use std::pin::Pin;
-use std::future::Future;
-
-use pin_project_lite::pin_project;
 
 use crate::stream::Stream;
 use crate::task::{Context, Poll};
 
-pin_project! {
-    /// A stream that yields elements by calling a closure.
-    ///
-    /// This stream is created by the [`from_fn`] function. See its
-    /// documentation for more.
-    ///
-    /// [`from_fn`]: fn.from_fn.html
-    #[derive(Debug)]
-    pub struct FromFn<F, Fut, T> {
-        f: F,
-        #[pin]
-        future: Option<Fut>,
-        __t: PhantomData<T>,
-    }
+/// A stream that yields elements by calling a closure.
+///
+/// This stream is created by the [`from_fn`] function. See its
+/// documentation for more.
+///
+/// [`from_fn`]: fn.from_fn.html
+#[derive(Clone, Debug)]
+pub struct FromFn<F> {
+    f: F,
 }
 
+impl<F> Unpin for FromFn<F> {}
+
 /// Creates a new stream where to produce each new element a provided closure is called.
 ///
 /// This allows creating a custom stream with any behaviour without using the more verbose
@@ -34,21 +27,15 @@ pin_project! {
 /// # async_std::task::block_on(async {
 /// #
 /// use async_std::prelude::*;
-/// use async_std::sync::{Arc, Mutex};
 /// use async_std::stream;
 ///
-/// let count = Arc::new(Mutex::new(0u8));
+/// let mut count = 0u8;
 /// let s = stream::from_fn(|| {
-///     let count = Arc::clone(&count);
-///
-///     async move {
-///         *count.lock().await += 1;
-///
-///         if *count.lock().await > 3 {
-///             None
-///         } else {
-///             Some(*count.lock().await)
-///         }
+///     count += 1;
+///     if count > 3 {
+///         None
+///     } else {
+///         Some(count)
 ///     }
 /// });
 ///
@@ -60,38 +47,21 @@ pin_project! {
 /// #
 /// # })
 /// ```
-pub fn from_fn<T, F, Fut>(f: F) -> FromFn<F, Fut, T>
+pub fn from_fn<T, F>(f: F) -> FromFn<F>
 where
-    F: FnMut() -> Fut,
-    Fut: Future<Output = Option<T>>,
+    F: FnMut() -> Option<T>,
 {
-    FromFn {
-        f,
-        future: None,
-        __t: PhantomData,
-    }
+    FromFn { f }
 }
 
-impl<F, Fut, T> Stream for FromFn<F, Fut, T>
+impl<T, F> Stream for FromFn<F>
 where
-    F: FnMut() -> Fut,
-    Fut: Future<Output = Option<T>>,
+    F: FnMut() -> Option<T>,
 {
     type Item = T;
 
-    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
-        let mut this = self.project();
-        loop {
-            if this.future.is_some() {
-                let next =
-                    futures_core::ready!(this.future.as_mut().as_pin_mut().unwrap().poll(cx));
-                this.future.set(None);
-
-                return Poll::Ready(next);
-            } else {
-                let fut = (this.f)();
-                this.future.set(Some(fut));
-            }
-        }
+    fn poll_next(mut self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        let item = (&mut self.f)();
+        Poll::Ready(item)
     }
 }

src/stream/from_iter.rs

@@ -6,7 +6,7 @@ use crate::stream::Stream;
 use crate::task::{Context, Poll};
 
 pin_project! {
-    /// A stream that created from iterator
+    /// A stream that was created from iterator.
     ///
     /// This stream is created by the [`from_iter`] function.
     /// See it documentation for more.

src/stream/mod.rs

@@ -306,9 +306,7 @@ pub use from_iter::{from_iter, FromIter};
 pub use once::{once, Once};
 pub use repeat::{repeat, Repeat};
 pub use repeat_with::{repeat_with, RepeatWith};
-pub use stream::{
-    Chain, Filter, Fuse, Inspect, Scan, Skip, SkipWhile, StepBy, Stream, Take, TakeWhile, Zip,
-};
+pub use stream::*;
 
 pub(crate) mod stream;
 

src/stream/once.rs

@@ -33,7 +33,7 @@ pin_project! {
     /// documentation for more.
     ///
     /// [`once`]: fn.once.html
-    #[derive(Debug)]
+    #[derive(Clone, Debug)]
     pub struct Once<T> {
         value: Option<T>,
     }

src/stream/repeat.rs

@@ -33,7 +33,7 @@ where
 /// documentation for more.
 ///
 /// [`repeat`]: fn.repeat.html
-#[derive(Debug)]
+#[derive(Clone, Debug)]
 pub struct Repeat<T> {
     item: T,
 }

src/stream/repeat_with.rs

@@ -1,28 +1,21 @@
-use std::marker::PhantomData;
 use std::pin::Pin;
-use std::future::Future;
-
-use pin_project_lite::pin_project;
 
 use crate::stream::Stream;
 use crate::task::{Context, Poll};
 
-pin_project! {
-    /// A stream that repeats elements of type `T` endlessly by applying a provided closure.
-    ///
-    /// This stream is created by the [`repeat_with`] function. See its
-    /// documentation for more.
-    ///
-    /// [`repeat_with`]: fn.repeat_with.html
-    #[derive(Debug)]
-    pub struct RepeatWith<F, Fut, A> {
-        f: F,
-        #[pin]
-        future: Option<Fut>,
-        __a: PhantomData<A>,
-    }
+/// A stream that repeats elements of type `T` endlessly by applying a provided closure.
+///
+/// This stream is created by the [`repeat_with`] function. See its
+/// documentation for more.
+///
+/// [`repeat_with`]: fn.repeat_with.html
+#[derive(Clone, Debug)]
+pub struct RepeatWith<F> {
+    f: F,
 }
 
+impl<F> Unpin for RepeatWith<F> {}
+
 /// Creates a new stream that repeats elements of type `A` endlessly by applying the provided closure.
 ///
 /// # Examples
@@ -35,7 +28,7 @@ pin_project! {
 /// use async_std::prelude::*;
 /// use async_std::stream;
 ///
-/// let s = stream::repeat_with(|| async { 1 });
+/// let s = stream::repeat_with(|| 1);
 ///
 /// pin_utils::pin_mut!(s);
 ///
@@ -54,48 +47,38 @@ pin_project! {
 /// use async_std::prelude::*;
 /// use async_std::stream;
 ///
-/// let s = stream::repeat_with(|| async { 1u8 }).take(2);
+/// let mut n = 1;
+/// let s = stream::repeat_with(|| {
+///     let item = n;
+///     n *= 2;
+///     item
+/// })
+/// .take(4);
 ///
 /// pin_utils::pin_mut!(s);
 ///
 /// assert_eq!(s.next().await, Some(1));
-/// assert_eq!(s.next().await, Some(1));
+/// assert_eq!(s.next().await, Some(2));
+/// assert_eq!(s.next().await, Some(4));
+/// assert_eq!(s.next().await, Some(8));
 /// assert_eq!(s.next().await, None);
 /// # })
 /// ```
-pub fn repeat_with<F, Fut, A>(repeater: F) -> RepeatWith<F, Fut, A>
+pub fn repeat_with<T, F>(repeater: F) -> RepeatWith<F>
 where
-    F: FnMut() -> Fut,
-    Fut: Future<Output = A>,
+    F: FnMut() -> T,
 {
-    RepeatWith {
-        f: repeater,
-        future: None,
-        __a: PhantomData,
-    }
+    RepeatWith { f: repeater }
 }
 
-impl<F, Fut, A> Stream for RepeatWith<F, Fut, A>
+impl<T, F> Stream for RepeatWith<F>
 where
-    F: FnMut() -> Fut,
-    Fut: Future<Output = A>,
+    F: FnMut() -> T,
 {
-    type Item = A;
-
-    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
-        let mut this = self.project();
-        loop {
-            if this.future.is_some() {
-                let res = futures_core::ready!(this.future.as_mut().as_pin_mut().unwrap().poll(cx));
-
-                this.future.set(None);
-
-                return Poll::Ready(Some(res));
-            } else {
-                let fut = (this.f)();
+    type Item = T;
 
-                this.future.set(Some(fut));
-            }
-        }
+    fn poll_next(mut self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        let item = (&mut self.f)();
+        Poll::Ready(Some(item))
     }
 }

src/stream/stream/chain.rs

@@ -7,7 +7,7 @@ use crate::prelude::*;
 use crate::task::{Context, Poll};
 
 pin_project! {
-    /// Chains two streams one after another.
+    /// A stream that chains two streams one after another.
     ///
     /// This `struct` is created by the [`chain`] method on [`Stream`]. See its
     /// documentation for more.

src/stream/stream/cloned.rs

@@ -4,6 +4,7 @@ use pin_project_lite::pin_project;
 use std::pin::Pin;
 
 pin_project! {
+    /// A stream that clones the elements of an underlying stream.
     #[derive(Debug)]
     pub struct Cloned<S> {
         #[pin]