fix:withDecay animation not starting if inital value is set to 0

packages/react-native-reanimated/src/animation/decay/decay.ts

@@ -113,6 +113,7 @@ export const withDecay = function (
       onFrame: decay,
       onStart,
       callback,
+      forceRunAnimation: true,
       velocity: config.velocity ?? 0,
       initialVelocity: 0,
       current: 0,

packages/react-native-reanimated/src/animation/decay/utils.ts

@@ -13,16 +13,23 @@ const IS_WEB = isWeb();
 export const VELOCITY_EPS = IS_WEB ? 1 / 20 : 1;
 export const SLOPE_FACTOR = 0.1;
 
+/*
+ * The `forceRunAnimation` prop is necessary to run withDecay animation when
+ * related sharedValue stays as `0`. It allows to skip animation check and start
+ * animation immediately
+ */
+
 export interface DecayAnimation extends Animation<DecayAnimation> {
   lastTimestamp: Timestamp;
   startTimestamp: Timestamp;
   initialVelocity: number;
   velocity: number;
   current: AnimatableValue;
+  forceRunAnimation: boolean;
 }
 
 export interface InnerDecayAnimation
-  extends Omit<DecayAnimation, 'current'>,
+  extends Omit<DecayAnimation, 'current' | 'forceRunAnimation'>,
     AnimationObject {
   current: number;
   springActive?: boolean;

packages/react-native-reanimated/src/valueSetter.ts

@@ -31,6 +31,7 @@ export function valueSetter<Value>(
     // built in animations that are not higher order(withTiming, withSpring) hold target value in .current
     if (
       mutable._value === animation.current &&
+      !animation.forceRunAnimation &&
       !animation.isHigherOrder &&
       !forceUpdate
     ) {