feat(core): Stream extension trait

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### Features
 
+- Added `SentryStream` and `SentryStreamExt` to `sentry-core`, which bind a `Hub` to a `Stream` so that it is polled within the given hub, mirroring the existing `SentryFuture` and `SentryFutureExt`. Use by bringing `SentryStreamExt` in scope and calling `bind_hub` on a stream ([#1214](https://github.com/getsentry/sentry-rust/pull/1214)).
 - The Tower integration's [`SentryHttpLayer`](https://docs.rs/sentry-tower/0.49.3/sentry_tower/struct.SentryHttpLayer.html) now records the [`http.response.status_code`](https://getsentry.github.io/sentry-conventions/attributes/http/) attribute on transactions ([#1253](https://github.com/getsentry/sentry-rust/pull/1253)).
 
 ### Deprecations

Cargo.toml

@@ -48,6 +48,7 @@ erased-serde = "0.3.12"
 esp-idf-svc = "0.51.0"
 findshlibs = "=0.10.2"
 futures = "0.3.24"
+futures-core = "0.3.24"
 futures-util = { version = "0.3.5", default-features = false }
 hex = "0.4.3"
 hostname = "0.4"

sentry-core/Cargo.toml

@@ -31,6 +31,7 @@ logs = []
 metrics = []
 
 [dependencies]
+futures-core = { workspace = true }
 log = { workspace = true, features = ["std"], optional = true }
 rand = { workspace = true, optional = true }
 sentry-types = { workspace = true }

sentry-core/src/lib.rs

@@ -118,6 +118,7 @@
 mod intodsn;
 mod performance;
 mod scope;
+mod stream;
 mod transport;
 
 // public api or exports from this crate
@@ -133,6 +134,7 @@
 pub use crate::intodsn::IntoDsn;
 pub use crate::performance::*;
 pub use crate::scope::{Scope, ScopeGuard};
+pub use crate::stream::{SentryStream, SentryStreamExt};
 pub use crate::transport::{Transport, TransportFactory, TransportOptions};
 #[cfg(feature = "logs")]
 mod logger; // structured logging macros exported with `#[macro_export]`

sentry-core/src/stream.rs

@@ -0,0 +1,131 @@
+use std::pin::Pin;
+use std::sync::Arc;
+use std::task::{Context, Poll};
+
+use futures_core::Stream;
+
+use crate::Hub;
+
+/// A stream that binds a `Hub` to its polling.
+///
+/// This activates the given hub for the duration of the inner stream's `poll_next`
+/// method. Users usually do not need to construct this type manually, but
+/// rather use the [`StreamExt::bind_hub`] method instead.
+///
+/// [`StreamExt::bind_hub`]: trait.StreamExt.html#method.bind_hub
+#[derive(Debug)]
+pub struct SentryStream<S> {
+    hub: Arc<Hub>,
+    stream: S,
+}
+
+impl<S> SentryStream<S> {
+    /// Creates a new bound stream with a `Hub`.
+    pub fn new(hub: Arc<Hub>, stream: S) -> Self {
+        Self { hub, stream }
+    }
+}
+
+impl<S> Stream for SentryStream<S>
+where
+    S: Stream,
+{
+    type Item = S::Item;
+
+    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        let hub = self.hub.clone();
+        // https://doc.rust-lang.org/std/pin/index.html#pinning-is-structural-for-field
+        let stream = unsafe { self.map_unchecked_mut(|s| &mut s.stream) };
+        #[cfg(feature = "client")]
+        {
+            let _guard = crate::hub_impl::SwitchGuard::new(hub);
+            stream.poll_next(cx)
+        }
+        #[cfg(not(feature = "client"))]
+        {
+            let _ = hub;
+            stream.poll_next(cx)
+        }
+    }
+}
+
+/// Stream extensions for Sentry.
+pub trait SentryStreamExt: Sized {
+    /// Binds a hub to this stream.
+    ///
+    /// This ensures that the stream is polled within the given hub.
+    fn bind_hub<H>(self, hub: H) -> SentryStream<Self>
+    where
+        H: Into<Arc<Hub>>,
+    {
+        SentryStream {
+            stream: self,
+            hub: hub.into(),
+        }
+    }
+}
+
+impl<S> SentryStreamExt for S where S: Stream {}
+
+#[cfg(all(test, feature = "test"))]
+mod tests {
+    use crate::test::with_captured_events;
+    use crate::{capture_error, capture_message, configure_scope, Hub, Level, SentryStreamExt};
+    use futures::StreamExt;
+    use tokio::runtime::Runtime;
+
+    #[derive(Debug)]
+    struct TestError(&'static str);
+
+    impl std::fmt::Display for TestError {
+        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            write!(f, "{}", self.0)
+        }
+    }
+
+    impl std::error::Error for TestError {}
+
+    #[test]
+    fn test_streams() {
+        let mut events = with_captured_events(|| {
+            let runtime = Runtime::new().unwrap();
+
+            // Two real streams, each bound to its own hub. The work inside each
+            // stream runs during `poll_next`, so the captured errors must end up
+            // tagged with the scope of the hub the stream was bound to.
+            runtime.block_on(async {
+                let stream1 = futures::stream::once(async {
+                    configure_scope(|scope| scope.set_transaction(Some("transaction1")));
+                    capture_error(&TestError("oh no from 1"));
+                })
+                .bind_hub(Hub::new_from_top(Hub::current()));
+
+                let stream2 = futures::stream::once(async {
+                    configure_scope(|scope| scope.set_transaction(Some("transaction2")));
+                    capture_error(&TestError("oh no from 2"));
+                })
+                .bind_hub(Hub::new_from_top(Hub::current()));
+
+                stream1.collect::<Vec<_>>().await;
+                stream2.collect::<Vec<_>>().await;
+            });
+
+            capture_message("oh hai from outside", Level::Info);
+        });
+
+        events.sort_by(|a, b| a.transaction.cmp(&b.transaction));
+        assert_eq!(events.len(), 3);
+
+        // The message captured outside any bound stream has no transaction and no
+        // exception, and sorts first.
+        assert_eq!(events[0].transaction, None);
+        assert!(events[0].exception.is_empty());
+
+        // The errors captured inside `poll_next` carry the scope of their bound
+        // hub and the expected exception payload.
+        assert_eq!(events[1].transaction, Some("transaction1".into()));
+        assert_eq!(events[1].exception[0].value, Some("oh no from 1".into()));
+        assert_eq!(events[2].transaction, Some("transaction2".into()));
+        assert_eq!(events[2].exception[0].value, Some("oh no from 2".into()));
+    }
+}