fix json conversion interface

- return partial data on conversion error in StatefulDecoder,
  to be in line with PlainDecoder and golang convention
- add err as return value for NewStatefulDecoder

2 files changed, 12 insertions, 8 deletions

diff --git a/src/hub/src/spreadspace.org/sfive/s5cvt.go b/src/hub/src/spreadspace.org/sfive/s5cvt.go
index 5a2ef70..d828af7 100644
--- a/src/hub/src/spreadspace.org/sfive/s5cvt.go
+++ b/src/hub/src/spreadspace.org/sfive/s5cvt.go
@@ -20,13 +20,14 @@ type PlainDecoder struct{}
 
 type PlainEncoder struct{}
 
-func NewStatefulDecoder(jsonString []byte) (decoder StatsDecoder) {
+func NewStatefulDecoder(jsonString []byte) (decoder StatsDecoder, err error) {
 	res := new(StatefulDecoder)
-	err := json.Unmarshal(jsonString, &res.sourceId)
+	err = json.Unmarshal(jsonString, &res.sourceId)
 	if err != nil {
-		return nil
+		return
 	}
-	return res
+	decoder = res
+	return
 }
 
 func NewPlainDecoder() (decoder StatsDecoder) {
@@ -35,10 +36,9 @@ func NewPlainDecoder() (decoder StatsDecoder) {
 
 func (self *StatefulDecoder) Decode(jsonString []byte) (dat StatisticsData, err error) {
 	err = json.Unmarshal(jsonString, &dat)
-	if err != nil {
-		return
-	}
 	dat.CopyFrom(&self.sourceId)
+	// like in PlainDecoder, let the client decide how to use partial results
+	// (Unmarshal returns partial results in case of errors)
 	return
 }
 
diff --git a/src/hub/src/spreadspace.org/sfive/s5cvt_test.go b/src/hub/src/spreadspace.org/sfive/s5cvt_test.go
index 5b53160..418d154 100644
--- a/src/hub/src/spreadspace.org/sfive/s5cvt_test.go
+++ b/src/hub/src/spreadspace.org/sfive/s5cvt_test.go
@@ -24,7 +24,11 @@ func GetExpected() *StatisticsData {
 }
 
 func TestDecodeStateful(t *testing.T) {
-	dc := NewStatefulDecoder([]byte(sourceIdData))
+	dc, err := NewStatefulDecoder([]byte(sourceIdData))
+	if err != nil {
+		t.Errorf("Creating decoder failed with %v", err)
+		return
+	}
 	dat, err := dc.Decode([]byte(testData))
 	if err != nil {
 		t.Errorf("Decode failed with %v", err)