keep non-nil array when last item is removed

Signed-off-by: dmitriy kalinin <dkalinin@pivotal.io>

Author: cppforlife

patch/array_insertion.go

@@ -57,7 +57,7 @@ func (i ArrayInsertion) Concrete() (ArrayInsertionIndex, error) {
 
 func (i ArrayInsertionIndex) Update(array []interface{}, obj interface{}) []interface{} {
 	if i.insert {
-		var newAry []interface{}
+		newAry := []interface{}{}
 		newAry = append(newAry, array[:i.number]...) // not inclusive
 		newAry = append(newAry, obj)
 		newAry = append(newAry, array[i.number:]...) // inclusive

patch/remove_op.go

@@ -34,7 +34,7 @@ func (op RemoveOp) Apply(doc interface{}) (interface{}, error) {
 			}
 
 			if isLast {
-				var newAry []interface{}
+				newAry := []interface{}{}
 				newAry = append(newAry, typedObj[:idx]...)
 				newAry = append(newAry, typedObj[idx+1:]...)
 				prevUpdate(newAry)
@@ -74,7 +74,7 @@ func (op RemoveOp) Apply(doc interface{}) (interface{}, error) {
 			}
 
 			if isLast {
-				var newAry []interface{}
+				newAry := []interface{}{}
 				newAry = append(newAry, typedObj[:idx]...)
 				newAry = append(newAry, typedObj[idx+1:]...)
 				prevUpdate(newAry)

patch/remove_op_test.go

@@ -31,6 +31,10 @@ var _ = Describe("RemoveOp.Apply", func() {
 			res, err = RemoveOp{Path: MustNewPointerFromString("/-1")}.Apply([]interface{}{1, 2, 3})
 			Expect(err).ToNot(HaveOccurred())
 			Expect(res).To(Equal([]interface{}{1, 2}))
+
+			res, err = RemoveOp{Path: MustNewPointerFromString("/0")}.Apply([]interface{}{1})
+			Expect(err).ToNot(HaveOccurred())
+			Expect(res).To(Equal([]interface{}{}))
 		})
 
 		It("removes relative array item", func() {
@@ -110,6 +114,16 @@ var _ = Describe("RemoveOp.Apply", func() {
 			}))
 		})
 
+		It("removes array item if found, leaving empty array", func() {
+			doc := []interface{}{
+				map[interface{}]interface{}{"key": "val"},
+			}
+
+			res, err := RemoveOp{Path: MustNewPointerFromString("/key=val")}.Apply(doc)
+			Expect(err).ToNot(HaveOccurred())
+			Expect(res).To(Equal([]interface{}{}))
+		})
+
 		It("removes relative array item", func() {
 			doc := []interface{}{
 				map[interface{}]interface{}{"key": "val"},