asyncreader: make ErrorStreamAbandoned public

fs/asyncreader/asyncreader.go

@@ -21,7 +21,8 @@ const (
 	bufferCacheFlushTime = 5 * time.Second // flush the cached buffers after this long
 )
 
-var errorStreamAbandoned = errors.New("stream abandoned")
+// ErrorStreamAbandoned is returned when the input is closed before the end of the stream
+var ErrorStreamAbandoned = errors.New("stream abandoned")
 
 // AsyncReader will do async read-ahead from the input reader
 // and make the data available as an io.Reader.
@@ -132,7 +133,7 @@ func (a *AsyncReader) fill() (err error) {
 		if !ok {
 			// Return an error to show fill failed
 			if a.err == nil {
-				return errorStreamAbandoned
+				return ErrorStreamAbandoned
 			}
 			return a.err
 		}

fs/asyncreader/asyncreader_test.go

@@ -279,7 +279,7 @@ func testAsyncReaderClose(t *testing.T, writeto bool) {
 	// Abandon the copy
 	a.Abandon()
 	wg.Wait()
-	assert.Equal(t, errorStreamAbandoned, copyErr)
+	assert.Equal(t, ErrorStreamAbandoned, copyErr)
 	// t.Logf("Copied %d bytes, err %v", copyN, copyErr)
 	assert.True(t, copyN > 0)
 }
@@ -353,7 +353,7 @@ func TestAsyncReaderSkipBytes(t *testing.T) {
 								if initialRead >= len(data) {
 									assert.Equal(t, err, io.EOF)
 								} else {
-									assert.True(t, err == errorStreamAbandoned || err == io.EOF)
+									assert.True(t, err == ErrorStreamAbandoned || err == io.EOF)
 								}
 							}
 						})