From 47588ba8f9a2ceb05acef2ec2c69263cf057405d Mon Sep 17 00:00:00 2001
From: Igor Oleinikov <igor@oleinikov.ru>
Date: Wed, 14 Sep 2016 11:27:33 -0700
Subject: [PATCH] [knockout] Introduce specialized signatures for subscribe
 method, specifically common "change" and "beforeChange" Add subscribe for
 "arrayChange" event for observable array (fixes #11203) Improve
 KnockoutArrayChange status typing.

---
 knockout/knockout.d.ts           | 11 ++++++++--
 knockout/knockoutamd-tests.ts    |  2 +-
 knockout/tests/knockout-tests.ts | 35 ++++++++++++++++++++++++++++++++
 3 files changed, 45 insertions(+), 3 deletions(-)

diff --git a/knockout/knockout.d.ts b/knockout/knockout.d.ts
index 6321cff0a5..f0e9fe023f 100644
--- a/knockout/knockout.d.ts
+++ b/knockout/knockout.d.ts
@@ -61,8 +61,10 @@ interface KnockoutSubscription {
 }
 
 interface KnockoutSubscribable<T> extends KnockoutSubscribableFunctions<T> {
-	subscribe(callback: (newValue: T) => void, target?: any, event?: string): KnockoutSubscription;
+    subscribe(callback: (newValue: T) => void, target: any, event: "beforeChange"): KnockoutSubscription;
+	subscribe(callback: (newValue: T) => void, target?: any, event?: "change"): KnockoutSubscription;
 	subscribe<TEvent>(callback: (newValue: TEvent) => void, target: any, event: string): KnockoutSubscription;
+
 	extend(requestedExtenders: { [key: string]: any; }): KnockoutSubscribable<T>;
 	getSubscriptionsCount(): number;
 }
@@ -91,6 +93,11 @@ interface KnockoutObservableArrayStatic {
 }
 
 interface KnockoutObservableArray<T> extends KnockoutObservable<T[]>, KnockoutObservableArrayFunctions<T> {
+    subscribe(callback: (newValue: KnockoutArrayChange<T>[]) => void, target: any, event: "arrayChange"): KnockoutSubscription;
+    subscribe(callback: (newValue: T[]) => void, target: any, event: "beforeChange"): KnockoutSubscription;
+    subscribe(callback: (newValue: T[]) => void, target?: any, event?: "change"): KnockoutSubscription;
+    subscribe<TEvent>(callback: (newValue: TEvent) => void, target: any, event: string): KnockoutSubscription;
+
     extend(requestedExtenders: { [key: string]: any; }): KnockoutObservableArray<T>;
 }
 
@@ -325,7 +332,7 @@ interface KnockoutUtils {
 }
 
 interface KnockoutArrayChange<T> {
-    status: string;
+    status: "added" | "deleted";
     value: T;
     index: number;
     moved?: number;
diff --git a/knockout/knockoutamd-tests.ts b/knockout/knockoutamd-tests.ts
index c874c6208b..9ee6658335 100644
--- a/knockout/knockoutamd-tests.ts
+++ b/knockout/knockoutamd-tests.ts
@@ -1,6 +1,6 @@
 /// <reference path="./knockout.d.ts" />
 
-import ko = require("knockout");
+import ko = require("knockout");
 
 var myArray = ko.observableArray([1, 2, 3]);
 
diff --git a/knockout/tests/knockout-tests.ts b/knockout/tests/knockout-tests.ts
index 8da6c12950..122617b180 100644
--- a/knockout/tests/knockout-tests.ts
+++ b/knockout/tests/knockout-tests.ts
@@ -680,3 +680,38 @@ function test_tasks() {
         setTimeout(callback, 0);
     };
 }
+
+function observableEventsTests() {
+    var observable = ko.observable(1);
+    observable.subscribe(value => {
+        var num: number = value;
+    });
+    observable.subscribe(value => {
+        var num: number = value;
+    }, null, "change");
+    observable.subscribe(value => {
+        var num: number = value;
+    }, null, "beforeChange");
+}
+
+function observableArrayEventsTests() {
+    var observableArray = ko.observableArray([1, 2, 3, 4]);
+    observableArray.subscribe(array => {
+        var arr: number[] = array;
+    });
+    observableArray.subscribe(array => {
+        var arr: number[] = array;
+    }, null, "change");
+    observableArray.subscribe(array => {
+        var arr: number[] = array;
+    }, null, "beforeChange");
+    var count = 0;
+    observableArray.subscribe(changes => {
+        changes.forEach(change => {
+            if (change.status == "added")
+                count++;
+            else if (change.status == "deleted")
+                count--;
+        });
+    }, null, "arrayChange");
+}
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