Support Holes in Array (#41)

* Support Holes in Array

* Use filter(() => true)

* Revert accidently changed line

Author: kateinoigakukun

IntegrationTests/TestSuites/Sources/PrimaryTests/main.swift

@@ -86,22 +86,36 @@ try test("Array Iterator") {
     let globalObject1 = getJSValue(this: .global, name: "globalObject1")
     let globalObject1Ref = try expectObject(globalObject1)
     let prop_4 = getJSValue(this: globalObject1Ref, name: "prop_4")
-    let array = try expectArray(prop_4)
+    let array1 = try expectArray(prop_4)
     let expectedProp_4: [JSValue] = [
         .number(3), .number(4), .string("str_elm_1"), .null, .undefined, .number(5),
     ]
-    try expectEqual(Array(array), expectedProp_4)
+    try expectEqual(Array(array1), expectedProp_4)
+
+    // Ensure that iterator skips empty hole as JavaScript does.
+    let prop_8 = getJSValue(this: globalObject1Ref, name: "prop_8")
+    let array2 = try expectArray(prop_8)
+    let expectedProp_8: [JSValue] = [0, 2, 3, 6]
+    try expectEqual(Array(array2), expectedProp_8)
 }
 
 try test("Array RandomAccessCollection") {
     let globalObject1 = getJSValue(this: .global, name: "globalObject1")
     let globalObject1Ref = try expectObject(globalObject1)
     let prop_4 = getJSValue(this: globalObject1Ref, name: "prop_4")
-    let array = try expectArray(prop_4)
+    let array1 = try expectArray(prop_4)
     let expectedProp_4: [JSValue] = [
         .number(3), .number(4), .string("str_elm_1"), .null, .undefined, .number(5),
     ]
-    try expectEqual([array[0], array[1], array[2], array[3], array[4], array[5]], expectedProp_4)
+    try expectEqual([array1[0], array1[1], array1[2], array1[3], array1[4], array1[5]], expectedProp_4)
+
+    // Ensure that subscript can access empty hole
+    let prop_8 = getJSValue(this: globalObject1Ref, name: "prop_8")
+    let array2 = try expectArray(prop_8)
+    let expectedProp_8: [JSValue] = [
+        0, .undefined, 2, 3, .undefined, .undefined, 6
+    ]
+    try expectEqual([array2[0], array2[1], array2[2], array2[3], array2[4], array2[5], array2[6]], expectedProp_8)
 }
 
 try test("Value Decoder") {

IntegrationTests/bin/primary-tests.js

@@ -23,6 +23,7 @@ global.globalObject1 = {
     }
   },
   "prop_7": 3.14,
+  "prop_8": [0, , 2, 3, , , 6],
 }
 
 global.Animal = function(name, age, isCat) {

Sources/JavaScriptKit/BasicObjects/JSArray.swift

@@ -28,11 +28,15 @@ extension JSArray: RandomAccessCollection {
         }
 
         public func next() -> Element? {
-            defer { index += 1 }
-            guard index < Int(ref.length.number!) else {
+            let currentIndex = index
+            guard currentIndex < Int(ref.length.number!) else {
                 return nil
             }
-            let value = ref[index]
+            index += 1
+            guard ref.hasOwnProperty!(currentIndex).boolean! else {
+                return next()
+            }
+            let value = ref[currentIndex]
             return value
         }
     }
@@ -43,7 +47,36 @@ extension JSArray: RandomAccessCollection {
 
     public var startIndex: Int { 0 }
 
-    public var endIndex: Int { ref.length.number.map(Int.init) ?? 0 }
+    public var endIndex: Int { length }
+
+    /// The number of elements in that array including empty hole.
+    /// Note that `length` respects JavaScript's `Array.prototype.length`
+    ///
+    /// e.g.
+    /// ```javascript
+    /// const array = [1, , 3];
+    /// ```
+    /// ```swift
+    /// let array: JSArray = ...
+    /// array.length // 3
+    /// array.count  // 2
+    /// ```
+    public var length: Int {
+        return Int(ref.length.number!)
+    }
+
+    /// The number of elements in that array **not** including empty hole.
+    /// Note that `count` syncs with the number that `Iterator` can iterate.
+    /// See also: `JSArray.length`
+    public var count: Int {
+        return getObjectValuesLength(ref)
+    }
+}
+
+private let alwaysTrue = JSClosure { _ in .boolean(true) }
+private func getObjectValuesLength(_ object: JSObject) -> Int {
+    let values = object.filter!(alwaysTrue).object!
+    return Int(values.length.number!)
 }
 
 extension JSValue {