Fix zero sized document crash

patch.go

@@ -721,6 +721,10 @@ func (p Patch) Apply(doc []byte) ([]byte, error) {
 // ApplyIndent mutates a JSON document according to the patch, and returns the new
 // document indented.
 func (p Patch) ApplyIndent(doc []byte, indent string) ([]byte, error) {
+	if len(doc) == 0 {
+		return doc, nil
+	}
+
 	var pd container
 	if doc[0] == '[' {
 		pd = &partialArray{}

patch_test.go

@@ -56,6 +56,13 @@ func repeatedA(r int) string {
 }
 
 var Cases = []Case{
+	{
+		``,
+		`[
+         { "op": "add", "path": "/baz", "value": "qux" }
+     ]`,
+		``,
+	},
 	{
 		`{ "foo": "bar"}`,
 		`[
@@ -518,8 +525,9 @@ func TestAdd(t *testing.T) {
 			key:  "-1",
 			val:  lazyNode{},
 			arr:  partialArray{},
+			err:  "Unable to access invalid index: -1: invalid index referenced",
+
 			rejectNegativeIndicies: true,
-			err: "Unable to access invalid index: -1: invalid index referenced",
 		},
 	}
 	for _, tc := range testCases {

v5/patch.go

@@ -27,7 +27,7 @@ var (
 	startObject                    = json.Delim('{')
 	endObject                      = json.Delim('}')
 	startArray                     = json.Delim('[')
-	endArray                     = json.Delim(']')
+	endArray                       = json.Delim(']')
 )
 
 var (
@@ -57,7 +57,7 @@ type Patch []Operation
 
 type partialDoc struct {
 	keys []string
-	obj   map[string]*lazyNode
+	obj  map[string]*lazyNode
 }
 
 type partialArray []*lazyNode
@@ -1026,6 +1026,10 @@ func (p Patch) ApplyIndent(doc []byte, indent string) ([]byte, error) {
 // ApplyIndentWithOptions mutates a JSON document according to the patch and the passed in ApplyOptions.
 // It returns the new document indented.
 func (p Patch) ApplyIndentWithOptions(doc []byte, indent string, options *ApplyOptions) ([]byte, error) {
+	if len(doc) == 0 {
+		return doc, nil
+	}
+
 	var pd container
 	if doc[0] == '[' {
 		pd = &partialArray{}

v5/patch_test.go

@@ -90,6 +90,15 @@ func repeatedA(r int) string {
 }
 
 var Cases = []Case{
+	{
+		``,
+		`[
+         { "op": "add", "path": "/baz", "value": "qux" }
+     ]`,
+		``,
+		false,
+		false,
+	},
 	{
 		`{ "foo": "bar"}`,
 		`[