From a8dfd3908106f5328e0fec82a1b1f86364edcc60 Mon Sep 17 00:00:00 2001
From: k1LoW <k1lowxb@gmail.com>
Date: Fri, 14 Feb 2020 10:36:33 +0900
Subject: [PATCH] Distinguish between empty slice and nil slice

---
 encode.go      |  6 +++++-
 encode_test.go | 28 +++++++++++++++++++++++++++-
 2 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/encode.go b/encode.go
index 413942e..7567bba 100644
--- a/encode.go
+++ b/encode.go
@@ -231,7 +231,11 @@ func (e *Encoder) encodeBool(v bool) ast.Node {
 }
 
 func (e *Encoder) encodeSlice(value reflect.Value) (ast.Node, error) {
-	sequence := ast.Sequence(token.New("-", "-", e.pos(e.column)), e.isFlowStyle)
+	isFlowStyle := e.isFlowStyle
+	if value.Len() == 0 && !value.IsNil() {
+		isFlowStyle = true
+	}
+	sequence := ast.Sequence(token.New("-", "-", e.pos(e.column)), isFlowStyle)
 	for i := 0; i < value.Len(); i++ {
 		node, err := e.encodeValue(value.Index(i), e.column)
 		if err != nil {
diff --git a/encode_test.go b/encode_test.go
index 06fcc26..e618952 100644
--- a/encode_test.go
+++ b/encode_test.go
@@ -189,7 +189,24 @@ func TestEncoder(t *testing.T) {
 				},
 			},
 		},
-
+		{
+			"a: 1\nb:\n\n",
+			struct {
+				A int
+				B []string
+			}{
+				1, ([]string)(nil),
+			},
+		},
+		{
+			"a: 1\nb: []\n",
+			struct {
+				A int
+				B []string
+			}{
+				1, []string{},
+			},
+		},
 		{
 			"a: b\nc: d\n",
 			struct {
@@ -265,6 +282,15 @@ func TestEncoder(t *testing.T) {
 				B float64 `yaml:"b,omitempty"`
 			}{1, 0},
 		},
+		{
+			"a: 1\n",
+			struct {
+				A int
+				B []string `yaml:"b,omitempty"`
+			}{
+				1, []string{},
+			},
+		},
 
 		// Flow flag
 		{