fix: support non-indexed deepObject array unmarshaling (#22)

deepobject.go

@@ -136,11 +136,16 @@ func UnmarshalDeepObject(dst interface{}, paramName string, params url.Values) e
 		if strings.HasPrefix(pName, searchStr) {
 			// trim the parameter name from the full name.
 			pName = pName[len(paramName):]
-			fieldNames = append(fieldNames, pName)
-			if len(pValues) != 1 {
-				return fmt.Errorf("%s has multiple values", pName)
+			if len(pValues) == 1 {
+				fieldNames = append(fieldNames, pName)
+				fieldValues = append(fieldValues, pValues[0])
+			} else {
+				// Non-indexed array format: expand repeated keys into indexed entries
+				for i, value := range pValues {
+					fieldNames = append(fieldNames, pName+"["+strconv.Itoa(i)+"]")
+					fieldValues = append(fieldValues, value)
+				}
 			}
-			fieldValues = append(fieldValues, pValues[0])
 		}
 	}
 

deepobject_test.go

@@ -170,3 +170,38 @@ func TestDeepObject_ArrayOfObjects(t *testing.T) {
 	assert.Equal(t, "second", dstArray[1].Name)
 	assert.Equal(t, "value2", dstArray[1].Value)
 }
+
+func TestDeepObject_NonIndexedArray(t *testing.T) {
+	t.Run("primitive string array", func(t *testing.T) {
+		params := url.Values{}
+		params.Add("p[vals]", "a")
+		params.Add("p[vals]", "b")
+
+		type Obj struct {
+			Vals []string `json:"vals"`
+		}
+
+		var dst Obj
+		err := UnmarshalDeepObject(&dst, "p", params)
+		require.NoError(t, err)
+		assert.Equal(t, []string{"a", "b"}, dst.Vals)
+	})
+
+	t.Run("object with mixed scalar and non-indexed array", func(t *testing.T) {
+		params := url.Values{}
+		params.Set("p[op]", "eq")
+		params.Add("p[vals]", "a")
+		params.Add("p[vals]", "b")
+
+		type Filter struct {
+			Op   string   `json:"op"`
+			Vals []string `json:"vals"`
+		}
+
+		var dst Filter
+		err := UnmarshalDeepObject(&dst, "p", params)
+		require.NoError(t, err)
+		assert.Equal(t, "eq", dst.Op)
+		assert.Equal(t, []string{"a", "b"}, dst.Vals)
+	})
+}