streamio.Reader: remember errors

If there has been an error, subsequent calls to Read should keep
returning that error.

Changelog: fixed

2 files changed, 21 insertions, 1 deletions

diff --git a/streamio/stream.go b/streamio/stream.go
index 0aab25315..68e6bd687 100644
--- a/streamio/stream.go
+++ b/streamio/stream.go
@@ -23,7 +23,7 @@ type receiveReader struct {
 }
 
 func (rr *receiveReader) Read(p []byte) (int, error) {
-	if len(rr.data) == 0 {
+	if len(rr.data) == 0 && rr.err == nil {
 		rr.data, rr.err = rr.receiver()
 	}
 
diff --git a/streamio/stream_test.go b/streamio/stream_test.go
index c91d5a58f..8f7c841fd 100644
--- a/streamio/stream_test.go
+++ b/streamio/stream_test.go
@@ -2,6 +2,7 @@ package streamio
 
 import (
 	"bytes"
+	"errors"
 	"fmt"
 	"io"
 	"strings"
@@ -60,6 +61,25 @@ func TestReadSizes(t *testing.T) {
 	})
 }
 
+func TestRead_rememberError(t *testing.T) {
+	firstRead := true
+	myError := errors.New("hello world")
+	r := NewReader(func() ([]byte, error) {
+		if firstRead {
+			firstRead = false
+			return nil, myError
+		}
+		panic("should never be reached")
+	})
+
+	// Intentionally call Read more than once. We want the error to be
+	// sticky.
+	for i := 0; i < 10; i++ {
+		_, err := r.Read(nil)
+		require.Equal(t, err, myError)
+	}
+}
+
 func receiverFromReader(r io.Reader) func() ([]byte, error) {
 	return func() ([]byte, error) {
 		data := make([]byte, 10)