Handle empty indexes for slices and arrays (eg. field[]=1&field[]=2)

Author: Maciej Mucha

decoder.go

@@ -75,6 +75,13 @@ func (d *decoder) parseMapData() {
 					log.Panicf(errMissingStartBracket, k)
 				}
 
+				insideBracket = false
+
+				// ignore empty key
+				if i == idx+1 {
+					continue
+				}
+
 				if rd = d.findAlias(k[:idx]); rd == nil {
 
 					l = len(d.dm) + 1
@@ -122,8 +129,6 @@ func (d *decoder) parseMapData() {
 				}
 
 				rd.keys = append(rd.keys, ke)
-
-				insideBracket = false
 			default:
 				// checking if not a number, 0-9 is 48-57 in byte, see for yourself fmt.Println('0', '1', '2', '3', '4', '5', '6', '7', '8', '9')
 				if insideBracket && (k[i] > 57 || k[i] < 48) {
@@ -356,16 +361,24 @@ func (d *decoder) setFieldByType(current reflect.Value, namespace []byte, idx in
 		d.parseMapData()
 		// slice elements could be mixed eg. number and non-numbers Value[0]=[]string{"10"} and Value=[]string{"10","20"}
 
-		if ok && len(arr) > 0 {
-			var varr reflect.Value
+		// handle also param[]=1&param[]=2 syntax
+		arraySuffix := []byte("[]")
+		suffixNamespace := append(namespace, arraySuffix...)
 
-			var ol int
+		for _, namespace := range [][]byte{namespace, suffixNamespace} {
+			arr, ok := d.values[string(namespace)]
 			l := len(arr)
 
+			if !ok || l == 0 {
+				continue
+			}
+
+			var varr reflect.Value
+			var ol int
+
 			if v.IsNil() {
-				varr = reflect.MakeSlice(v.Type(), len(arr), len(arr))
+				varr = reflect.MakeSlice(v.Type(), l, l)
 			} else {
-
 				ol = v.Len()
 				l += ol
 
@@ -456,14 +469,25 @@ func (d *decoder) setFieldByType(current reflect.Value, namespace []byte, idx in
 
 	case reflect.Array:
 		d.parseMapData()
-
 		// array elements could be mixed eg. number and non-numbers Value[0]=[]string{"10"} and Value=[]string{"10","20"}
 
-		if ok && len(arr) > 0 {
-			var varr reflect.Value
+		// handle also param[]=1&param[]=2 syntax
+		arraySuffix := []byte("[]")
+		suffixNamespace := append(namespace, arraySuffix...)
+
+		var ol int
+
+		for _, namespace := range [][]byte{namespace, suffixNamespace} {
+			arr, ok := d.values[string(namespace)]
 			l := len(arr)
-			overCapacity := v.Len() < l
-			if overCapacity {
+
+			if !ok || l == 0 {
+				continue
+			}
+
+			var varr reflect.Value
+
+			if v.Len() < l {
 				// more values than array capacity, ignore values over capacity as it's possible some would just want
 				// to grab the first x number of elements; in the future strict mode logic should return an error
 				fmt.Println("warning number of post form array values is larger than array capacity, ignoring overflow values")
@@ -474,15 +498,19 @@ func (d *decoder) setFieldByType(current reflect.Value, namespace []byte, idx in
 			if v.Len() < len(arr) {
 				l = v.Len()
 			}
-			for i := 0; i < l; i++ {
+			l += ol
+
+			for i := ol; i < l; i++ {
 				newVal := reflect.New(v.Type().Elem()).Elem()
 
-				if d.setFieldByType(newVal, namespace, i) {
+				if d.setFieldByType(newVal, namespace, i-ol) {
 					set = true
 					varr.Index(i).Set(newVal)
 				}
 			}
+
 			v.Set(varr)
+			ol = l
 		}
 
 		// maybe it's an numbered array i.e. Phone[0].Number

decoder_test.go

@@ -1910,29 +1910,41 @@ func TestDecoder_EmptyArrayBool(t *testing.T) {
 	Equal(t, err, nil)
 }
 
-func TestDecoder_InvalidSliceIndex(t *testing.T) {
+func TestDecoder_ArrayIndexes(t *testing.T) {
 	type PostsRequest struct {
-		PostIds []string
+		StrSlice              []string
+		MapOfStrSlice         map[string][]string
+		StrSliceExplicitField []string `form:"StrArrExplicitField[]"`
+		StrArr                [4]string
 	}
 	in := url.Values{
-		"PostIds[]": []string{"1", "2"},
+		"StrArr":                 []string{"0"},
+		"StrArr[]":               []string{"1", "2"},
+		"StrArr[3]":              []string{"3"},
+		"StrSlice":               []string{"0"},
+		"StrSlice[]":             []string{"1", "2"},
+		"StrSlice[3]":            []string{"3"},
+		"MapOfStrSlice[test1][]": []string{"0", "1"},
+		"StrArrExplicitField[]":  []string{"0", "1"},
 	}
 
 	v := new(PostsRequest)
 	d := NewDecoder()
 	err := d.Decode(v, in)
-	NotEqual(t, err, nil)
-	Equal(t, err.Error(), "Field Namespace:PostIds ERROR:invalid slice index ''")
-
-	// No error with proper name
-	type PostsRequest2 struct {
-		PostIds []string `form:"PostIds[]"`
-	}
-
-	v2 := new(PostsRequest2)
-	err = d.Decode(v2, in)
 	Equal(t, err, nil)
-	Equal(t, len(v2.PostIds), 2)
-	Equal(t, v2.PostIds[0], "1")
-	Equal(t, v2.PostIds[1], "2")
+	Equal(t, len(v.StrSlice), 4)
+	Equal(t, v.StrSlice[0], "0")
+	Equal(t, v.StrSlice[1], "1")
+	Equal(t, v.StrSlice[2], "2")
+	Equal(t, v.StrSlice[3], "3")
+	Equal(t, len(v.StrArr), 4)
+	Equal(t, v.StrArr[0], "0")
+	Equal(t, v.StrArr[1], "1")
+	Equal(t, v.StrArr[2], "2")
+	Equal(t, v.StrArr[3], "3")
+	Equal(t, len(v.MapOfStrSlice["test1"]), 2)
+	Equal(t, v.MapOfStrSlice["test1"][0], "0")
+	Equal(t, v.MapOfStrSlice["test1"][1], "1")
+	Equal(t, v.StrSliceExplicitField[0], "0")
+	Equal(t, v.StrSliceExplicitField[1], "1")
 }