Fixed empty array json bug #1880

Author: mikefarah

pkg/yqlib/candidiate_node_json.go

@@ -162,8 +162,13 @@ func (o *CandidateNode) MarshalJSON() ([]byte, error) {
 		buf.WriteByte('}')
 		return buf.Bytes(), nil
 	case SequenceNode:
-		log.Debugf("MarshalJSON SequenceNode")
-		err := enc.Encode(o.Content)
+		log.Debugf("MarshalJSON SequenceNode, %v, len: %v", o.Content, len(o.Content))
+		var err error
+		if len(o.Content) == 0 {
+			buf.WriteString("[]")
+		} else {
+			err = enc.Encode(o.Content)
+		}
 		return buf.Bytes(), err
 	default:
 		err := enc.Encode(nil)

pkg/yqlib/json_test.go

@@ -80,6 +80,27 @@ const roundTripMultiLineJson = `{
 `
 
 var jsonScenarios = []formatScenario{
+	{
+		description:  "array empty",
+		skipDoc:      true,
+		input:        "[]",
+		scenarioType: "roundtrip-ndjson",
+		expected:     "[]\n",
+	},
+	{
+		description:  "array has scalar",
+		skipDoc:      true,
+		input:        "[3]",
+		scenarioType: "roundtrip-ndjson",
+		expected:     "[3]\n",
+	},
+	{
+		description:  "array has object",
+		skipDoc:      true,
+		input:        `[{"x": 3}]`,
+		scenarioType: "roundtrip-ndjson",
+		expected:     "[{\"x\":3}]\n",
+	},
 	{
 		description:  "array null",
 		skipDoc:      true,