chore: checkpoint before Python removal

vendor/tower/src/discover/list.rs

@@ -0,0 +1,62 @@
+use super::Change;
+use futures_core::Stream;
+use pin_project_lite::pin_project;
+use std::convert::Infallible;
+use std::iter::{Enumerate, IntoIterator};
+use std::{
+    pin::Pin,
+    task::{Context, Poll},
+};
+use tower_service::Service;
+
+pin_project! {
+    /// Static service discovery based on a predetermined list of services.
+    ///
+    /// [`ServiceList`] is created with an initial list of services. The discovery
+    /// process will yield this list once and do nothing after.
+    #[derive(Debug)]
+    pub struct ServiceList<T>
+    where
+        T: IntoIterator,
+    {
+        inner: Enumerate<T::IntoIter>,
+    }
+}
+
+impl<T, U> ServiceList<T>
+where
+    T: IntoIterator<Item = U>,
+{
+    #[allow(missing_docs)]
+    pub fn new<Request>(services: T) -> ServiceList<T>
+    where
+        U: Service<Request>,
+    {
+        ServiceList {
+            inner: services.into_iter().enumerate(),
+        }
+    }
+}
+
+impl<T, U> Stream for ServiceList<T>
+where
+    T: IntoIterator<Item = U>,
+{
+    type Item = Result<Change<usize, U>, Infallible>;
+
+    fn poll_next(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        match self.project().inner.next() {
+            Some((i, service)) => Poll::Ready(Some(Ok(Change::Insert(i, service)))),
+            None => Poll::Ready(None),
+        }
+    }
+}
+
+// check that List can be directly over collections
+#[cfg(test)]
+#[allow(dead_code)]
+type ListVecTest<T> = ServiceList<Vec<T>>;
+
+#[cfg(test)]
+#[allow(dead_code)]
+type ListVecIterTest<T> = ServiceList<::std::vec::IntoIter<T>>;

vendor/tower/src/discover/mod.rs

@@ -0,0 +1,107 @@
+//! Service discovery
+//!
+//! This module provides the [`Change`] enum, which indicates the arrival or departure of a service
+//! from a collection of similar services. Most implementations should use the [`Discover`] trait
+//! in their bounds to indicate that they can handle services coming and going. [`Discover`] itself
+//! is primarily a convenience wrapper around [`TryStream<Ok = Change>`][`TryStream`].
+//!
+//! Every discovered service is assigned an identifier that is distinct among the currently active
+//! services. If that service later goes away, a [`Change::Remove`] is yielded with that service's
+//! identifier. From that point forward, the identifier may be re-used.
+//!
+//! # Examples
+//!
+//! ```rust
+//! use std::future::poll_fn;
+//! use futures_util::pin_mut;
+//! use tower::discover::{Change, Discover};
+//! async fn services_monitor<D: Discover>(services: D) {
+//!     pin_mut!(services);
+//!     while let Some(Ok(change)) = poll_fn(|cx| services.as_mut().poll_discover(cx)).await {
+//!         match change {
+//!             Change::Insert(key, svc) => {
+//!                 // a new service with identifier `key` was discovered
+//!                 # let _ = (key, svc);
+//!             }
+//!             Change::Remove(key) => {
+//!                 // the service with identifier `key` has gone away
+//!                 # let _ = (key);
+//!             }
+//!         }
+//!     }
+//! }
+//! ```
+//!
+//! [`TryStream`]: https://docs.rs/futures/latest/futures/stream/trait.TryStream.html
+
+mod list;
+
+pub use self::list::ServiceList;
+
+use crate::sealed::Sealed;
+use futures_core::TryStream;
+use std::{
+    pin::Pin,
+    task::{Context, Poll},
+};
+
+/// A dynamically changing set of related services.
+///
+/// As new services arrive and old services are retired,
+/// [`Change`]s are returned which provide unique identifiers
+/// for the services.
+///
+/// See the module documentation for more details.
+pub trait Discover: Sealed<Change<(), ()>> {
+    /// A unique identifier for each active service.
+    ///
+    /// An identifier can be re-used once a [`Change::Remove`] has been yielded for its service.
+    type Key: Eq;
+
+    /// The type of [`Service`] yielded by this [`Discover`].
+    ///
+    /// [`Service`]: crate::Service
+    type Service;
+
+    /// Error produced during discovery
+    type Error;
+
+    /// Yields the next discovery change set.
+    fn poll_discover(
+        self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+    ) -> Poll<Option<Result<Change<Self::Key, Self::Service>, Self::Error>>>;
+}
+
+impl<K, S, E, D: ?Sized> Sealed<Change<(), ()>> for D
+where
+    D: TryStream<Ok = Change<K, S>, Error = E>,
+    K: Eq,
+{
+}
+
+impl<K, S, E, D: ?Sized> Discover for D
+where
+    D: TryStream<Ok = Change<K, S>, Error = E>,
+    K: Eq,
+{
+    type Key = K;
+    type Service = S;
+    type Error = E;
+
+    fn poll_discover(
+        self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+    ) -> Poll<Option<Result<D::Ok, D::Error>>> {
+        TryStream::try_poll_next(self, cx)
+    }
+}
+
+/// A change in the service set.
+#[derive(Debug, Clone)]
+pub enum Change<K, V> {
+    /// A new service identified by key `K` was identified.
+    Insert(K, V),
+    /// The service identified by key `K` disappeared.
+    Remove(K),
+}