1 files changed, 143 insertions, 0 deletions
diff --git a/helix-lsp/src/select_all.rs b/helix-lsp/src/select_all.rs
new file mode 100644
index 00000000..987f2a10
--- /dev/null
+++ b/helix-lsp/src/select_all.rs
@@ -0,0 +1,143 @@
+//! An unbounded set of streams
+
+use core::fmt::{self, Debug};
+use core::iter::FromIterator;
+use core::pin::Pin;
+
+use smol::ready;
+use smol::stream::Stream;
+use std::task::{Context, Poll};
+
+use futures_util::stream::FusedStream;
+use futures_util::stream::{FuturesUnordered, StreamExt, StreamFuture};
+
+/// An unbounded set of streams
+///
+/// This "combinator" provides the ability to maintain a set of streams
+/// and drive them all to completion.
+///
+/// Streams are pushed into this set and their realized values are
+/// yielded as they become ready. Streams will only be polled when they
+/// generate notifications. This allows to coordinate a large number of streams.
+///
+/// Note that you can create a ready-made `SelectAll` via the
+/// `select_all` function in the `stream` module, or you can start with an
+/// empty set with the `SelectAll::new` constructor.
+#[must_use = "streams do nothing unless polled"]
+pub struct SelectAll<St> {
+    inner: FuturesUnordered<StreamFuture<St>>,
+}
+
+impl<St: Debug> Debug for SelectAll<St> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "SelectAll {{ ... }}")
+    }
+}
+
+impl<St: Stream + Unpin> SelectAll<St> {
+    /// Constructs a new, empty `SelectAll`
+    ///
+    /// The returned `SelectAll` does not contain any streams and, in this
+    /// state, `SelectAll::poll` will return `Poll::Ready(None)`.
+    pub fn new() -> Self {
+        Self {
+            inner: FuturesUnordered::new(),
+        }
+    }
+
+    /// Returns the number of streams contained in the set.
+    ///
+    /// This represents the total number of in-flight streams.
+    pub fn len(&self) -> usize {
+        self.inner.len()
+    }
+
+    /// Returns `true` if the set contains no streams
+    pub fn is_empty(&self) -> bool {
+        self.inner.is_empty()
+    }
+
+    /// Push a stream into the set.
+    ///
+    /// This function submits the given stream to the set for managing. This
+    /// function will not call `poll` on the submitted stream. The caller must
+    /// ensure that `SelectAll::poll` is called in order to receive task
+    /// notifications.
+    pub fn push(&self, stream: St) {
+        self.inner.push(stream.into_future());
+    }
+}
+
+impl<St: Stream + Unpin> Default for SelectAll<St> {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl<St: Stream + Unpin> Stream for SelectAll<St> {
+    type Item = St::Item;
+
+    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        loop {
+            match ready!(self.inner.poll_next_unpin(cx)) {
+                Some((Some(item), remaining)) => {
+                    self.push(remaining);
+                    return Poll::Ready(Some(item));
+                }
+                Some((None, _)) => {
+                    // `FuturesUnordered` thinks it isn't terminated
+                    // because it yielded a Some.
+                    // We do not return, but poll `FuturesUnordered`
+                    // in the next loop iteration.
+                }
+                None => return Poll::Ready(None),
+            }
+        }
+    }
+}
+
+impl<St: Stream + Unpin> FusedStream for SelectAll<St> {
+    fn is_terminated(&self) -> bool {
+        self.inner.is_terminated()
+    }
+}
+
+/// Convert a list of streams into a `Stream` of results from the streams.
+///
+/// This essentially takes a list of streams (e.g. a vector, an iterator, etc.)
+/// and bundles them together into a single stream.
+/// The stream will yield items as they become available on the underlying
+/// streams internally, in the order they become available.
+///
+/// Note that the returned set can also be used to dynamically push more
+/// futures into the set as they become available.
+///
+/// This function is only available when the `std` or `alloc` feature of this
+/// library is activated, and it is activated by default.
+pub fn select_all<I>(streams: I) -> SelectAll<I::Item>
+where
+    I: IntoIterator,
+    I::Item: Stream + Unpin,
+{
+    let mut set = SelectAll::new();
+
+    for stream in streams {
+        set.push(stream);
+    }
+
+    set
+}
+
+impl<St: Stream + Unpin> FromIterator<St> for SelectAll<St> {
+    fn from_iter<T: IntoIterator<Item = St>>(iter: T) -> Self {
+        select_all(iter)
+    }
+}
+
+impl<St: Stream + Unpin> Extend<St> for SelectAll<St> {
+    fn extend<T: IntoIterator<Item = St>>(&mut self, iter: T) {
+        for st in iter {
+            self.push(st)
+        }
+    }
+}