Fix merge arrays with new value (#502)

Author: nzagorchev

LeanplumSDK/LeanplumSDK/ClassesSwift/ContentMerger.swift

@@ -91,13 +91,15 @@ import Foundation
 
                     let newValue = diffDict[keyStr] ?? NSNull()
                     // Value index is bigger than default array count
-                    // the value is a new one, append it to the array
-                    if merged.count <= i {
-                        merged.append(merge(vars: merged[i], diff: newValue))
-                    } else {
-                        // The new value overrides existing value at index
-                        merged[i] = merge(vars: merged[i], diff: newValue)
+                    // Fill the array with null values
+                    if i >= merged.count {
+                        while i >= merged.count {
+                            merged.append(NSNull())
+                        }
                     }
+                    
+                    // Override the default value at index
+                    merged[i] = merge(vars: merged[i], diff: newValue)
                 }
             }
             return merged

LeanplumSDKApp/LeanplumSDKTests/Classes/ContentMergerTest.swift

@@ -36,14 +36,30 @@ class ContentMergerTest: XCTestCase {
         XCTAssertEqual(arrMixed, result)
     }
 
-    func testMergeArraysWithDict() {
+    func testMergeArrayWithDict() {
         let arr: [AnyHashable] = [1, 2, 3, 4]
         let arrDiff: AnyDictionary = ["[0]": 5, "[3]": 6]
         let expected: [AnyHashable] = [5, 2, 3, 6]
         let result = ContentMerger.merge(vars: arr, diff: arrDiff) as! [AnyHashable]
         XCTAssertEqual(expected, result)
     }
 
+    func testMergeArrayWithDictAdditionalValue() {
+        let arr: [AnyHashable] = [1, 2, 3, 4]
+        let arrDiff: AnyDictionary = ["[4]": 5]
+        let expected: [AnyHashable] = [1, 2, 3, 4, 5]
+        let result = ContentMerger.merge(vars: arr, diff: arrDiff) as! [AnyHashable]
+        XCTAssertEqual(expected, result)
+    }
+    
+    func testMergeEmptyArrayWithDict() {
+        let arr: [AnyHashable] = []
+        let arrDiff: AnyDictionary = ["[4]": 5]
+        let expected: [AnyHashable] = [NSNull(), NSNull(), NSNull(), NSNull(), 5]
+        let result = ContentMerger.merge(vars: arr, diff: arrDiff) as! [AnyHashable]
+        XCTAssertEqual(expected, result)
+    }
+    
     func testMergeArraysMixed() {
         let arr: [AnyHashable] = [1, 2, "value", 4, NSNull()]
         let arrDiff: AnyDictionary = ["[0]": 6, "[2]": "newValue", "[4]": "anotherValue"]