WIP testing cbor output

crates/streams/src/firsterr.rs

@@ -0,0 +1,32 @@
+use crate::cbor::CborBytes;
+use futures_util::future;
+use futures_util::Stream;
+use futures_util::StreamExt;
+
+pub fn non_empty<S, E>(inp: S) -> impl Stream<Item = Result<CborBytes, E>>
+where
+    S: Stream<Item = Result<CborBytes, E>>,
+{
+    inp.filter(|x| {
+        future::ready(match x {
+            Ok(x) => x.len() > 0,
+            Err(_) => true,
+        })
+    })
+}
+
+pub fn only_first_err<S, T, E>(inp: S) -> impl Stream<Item = Result<T, E>>
+where
+    S: Stream<Item = Result<T, E>>,
+{
+    inp.take_while({
+        let mut state = true;
+        move |x| {
+            let ret = state;
+            if x.is_err() {
+                state = false;
+            }
+            future::ready(ret)
+        }
+    })
+}