From fea2db42fdbbb4e9cf6420f77048c7dab47b4ef0 Mon Sep 17 00:00:00 2001
From: Christopher Chedeau <vjeux@fb.com>
Date: Wed, 22 Jul 2015 17:20:27 -0700
Subject: [PATCH] [Animated] Send a final update with toValue for spring

Summary:
Animated.spring is not guarantee to stabilize at exactly toValue (determined by restDisplacementThreshold). It is a bit annoying that the last value is not toValue, it makes the logs harder to read and also prevents you from writing code like value === toValue. Instead you need to track it down somewhere else.
---
 Libraries/Animation/Animated/Animated.js            |  6 ++++++
 .../Animation/Animated/__tests__/Animated-test.js   | 13 +++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/Libraries/Animation/Animated/Animated.js b/Libraries/Animation/Animated/Animated.js
index f99913f50..8f3f38398 100644
--- a/Libraries/Animation/Animated/Animated.js
+++ b/Libraries/Animation/Animated/Animated.js
@@ -479,7 +479,13 @@ class SpringAnimation extends Animation {
     if (this._tension !== 0) {
       isDisplacement = Math.abs(this._toValue - position) <= this._restDisplacementThreshold;
     }
+
     if (isOvershooting || (isVelocity && isDisplacement)) {
+      if (this._tension !== 0) {
+        // Ensure that we end up with a round value
+        this._onUpdate(this._toValue);
+      }
+
       this.__debouncedOnEnd({finished: true});
       return;
     }
diff --git a/Libraries/Animation/Animated/__tests__/Animated-test.js b/Libraries/Animation/Animated/__tests__/Animated-test.js
index cad752ff0..d27ff920c 100644
--- a/Libraries/Animation/Animated/__tests__/Animated-test.js
+++ b/Libraries/Animation/Animated/__tests__/Animated-test.js
@@ -127,6 +127,19 @@ describe('Animated', () => {
     Animated.spring(anim, {toValue: 0, velocity: 0}).start(callback);
     expect(callback).toBeCalled();
   });
+
+  it('send toValue when a spring stops', () => {
+    var anim = new Animated.Value(0);
+    var listener = jest.genMockFunction();
+    anim.addListener(listener);
+    Animated.spring(anim, {toValue: 15}).start();
+    jest.runAllTimers();
+    var lastValue = listener.mock.calls[listener.mock.calls.length - 2][0].value;
+    expect(lastValue).not.toBe(15);
+    expect(lastValue).toBeCloseTo(15);
+    expect(anim.__getValue()).toBe(15);
+  });
+
 });