Try to wrap stream into SCC to factor the errored and completed checks

netpod/src/lib.rs

@@ -10,6 +10,8 @@ use timeunits::*;
 #[allow(unused_imports)]
 use tracing::{debug, error, info, trace, warn};
 
+pub mod streamext;
+
 #[derive(Clone, Debug, Serialize, Deserialize)]
 pub struct AggQuerySingleChannel {
     pub channel_config: ChannelConfig,

netpod/src/streamext.rs

@@ -0,0 +1,72 @@
+use err::Error;
+use futures_core::Stream;
+use futures_util::StreamExt;
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
+pub struct SCC<S>
+where
+    S: Stream,
+{
+    inp: S,
+    errored: bool,
+    completed: bool,
+}
+
+impl<S> SCC<S>
+where
+    S: Stream,
+{
+    pub fn new(inp: S) -> Self {
+        Self {
+            inp,
+            errored: false,
+            completed: false,
+        }
+    }
+}
+
+impl<S, I> Stream for SCC<S>
+where
+    S: Stream<Item = Result<I, Error>> + Unpin,
+{
+    type Item = <S as Stream>::Item;
+    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<Option<Self::Item>> {
+        use Poll::*;
+        if self.completed {
+            panic!("poll_next on completed");
+        } else if self.errored {
+            self.completed = true;
+            Ready(None)
+        } else {
+            match self.inp.poll_next_unpin(cx) {
+                Ready(Some(Ok(k))) => Ready(Some(Ok(k))),
+                Ready(Some(Err(e))) => {
+                    self.errored = true;
+                    Ready(Some(Err(e)))
+                }
+                Ready(None) => {
+                    self.completed = true;
+                    Ready(None)
+                }
+                Pending => Pending,
+            }
+        }
+    }
+}
+
+pub trait IntoSCC<S>
+where
+    S: Stream,
+{
+    fn into_scc(self) -> SCC<S>;
+}
+
+impl<S> IntoSCC<S> for S
+where
+    S: Stream,
+{
+    fn into_scc(self) -> SCC<S> {
+        SCC::new(self)
+    }
+}