fix(compareArray): fix adding duplicate items to arrays not generating a add operation

Previously it was only checked if an object was in an array. We now keep track of indexes of objects that have been found and only allow an object to be found once. This fixes adding duplicate arrays because the objects are essentially seen as being different now.

Author: epelc

jsonpatch.go

@@ -214,9 +214,10 @@ func handleValues(av, bv interface{}, p string, patch []JsonPatchOperation) ([]J
 
 func compareArray(av, bv []interface{}, p string) []JsonPatchOperation {
 	retval := []JsonPatchOperation{}
-	//	var err error
+
 	for i, v := range av {
 		found := false
+		// NOTE it is fine to range over all of bv since we are just removing elements.
 		for _, v2 := range bv {
 			if reflect.DeepEqual(v, v2) {
 				found = true
@@ -227,14 +228,27 @@ func compareArray(av, bv []interface{}, p string) []JsonPatchOperation {
 		}
 	}
 
+	// Find elements that need to be added.
+	// NOTE we keep track of which indexes we've already found so that duplicate objects work correctly.
+	foundIndexes := make(map[int]int, len(bv))
 	for i, v := range bv {
-		found := false
-		for _, v2 := range av {
+		for i2, v2 := range av {
+			alreadyFoundThisIndex := true
+			for _, foundI2 := range foundIndexes {
+				if foundI2 == i2 {
+					alreadyFoundThisIndex = false
+					break
+				}
+			}
+			if !alreadyFoundThisIndex {
+				continue
+			}
 			if reflect.DeepEqual(v, v2) {
-				found = true
+				foundIndexes[i] = i2
+				break
 			}
 		}
-		if !found {
+		if _, ok := foundIndexes[i]; !ok {
 			retval = append(retval, NewPatch("add", makePath(p, i), v))
 		}
 	}

jsonpatch_array_test.go

@@ -0,0 +1,37 @@
+package jsonpatch
+
+import (
+	"sort"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+var arrayBase = `{
+  "persons": [{"name":"Ed"},{}]
+}`
+
+var arrayUpdated = `{
+  "persons": [{"name":"Ed"},{},{}]
+}`
+
+func TestArrayAddMultipleEmptyObjects(t *testing.T) {
+	patch, e := CreatePatch([]byte(arrayBase), []byte(arrayUpdated))
+	assert.NoError(t, e)
+	t.Log("Patch:", patch)
+	assert.Equal(t, 1, len(patch), "they should be equal")
+	sort.Sort(ByPath(patch))
+
+	change := patch[0]
+	assert.Equal(t, "add", change.Operation, "they should be equal")
+	assert.Equal(t, "/persons/2", change.Path, "they should be equal")
+	assert.Equal(t, map[string]interface{}{}, change.Value, "they should be equal")
+	// change = patch[1]
+	// assert.Equal(t, "add", change.Operation, "they should be equal")
+	// assert.Equal(t, "/goods/2/batters/batter/2", change.Path, "they should be equal")
+	// assert.Equal(t, map[string]interface{}{"id": "1003", "type": "Vanilla"}, change.Value, "they should be equal")
+	// change = patch[2]
+	// assert.Equal(t, change.Operation, "remove", "they should be equal")
+	// assert.Equal(t, change.Path, "/goods/2/topping/2", "they should be equal")
+	// assert.Equal(t, nil, change.Value, "they should be equal")
+}