Animated: Minimize AnimatedProps Invalidation (#46386)

Summary:
Pull Request resolved: #46386

Currently, `useAnimatedProps` attempts (and fails) to memoize the `AnimatedProps` instance by using `props` in the dependency array:

https://www.internalfb.com/code/fbsource/[de6bf108ae11fad0e8516617cde6f0cf3152d129]/xplat/js/react-native-github/packages/react-native/Libraries/Animated/useAnimatedProps.js?lines=56-59

However, `props` is very easily invalidated whenever the component is updated by its parent. The only time when it will not be invalidated is if the component that directly uses this hook — `createAnimatedComponent`'s return value — updates state… which never happens.

This changes `useAnimatedProps` so that we memoize `AnimatedProps` using only the nested property values that actually require a new `AnimatedProps` object to be created, which are `AnimatedNode` subclasses.

A minor detail is that in order for `AnimatedProps.prototype.__getValue` to continue working, we must supply `props` when we're actualizing the `AnimatedNode` instances into real values. This is accomplished by introducing a new method to select `AnimatedNode` subclasses: `__getValueFromStatic{Props,Object,Style,Transforms}`

Changelog:
[General][Added] - Created an experimental optimization to improve memoization within `Animated` to improve product performance

Reviewed By: javache

Differential Revision: D61997128

fbshipit-source-id: 2ca3cfb1038ba9a0abd82904acbc5cb4eb41a45d

packages/react-native/Libraries/Animated/nodes/AnimatedObject.js

@@ -19,9 +19,11 @@ import * as React from 'react';
 
 const MAX_DEPTH = 5;
 
-/* $FlowIssue[incompatible-type-guard] - Flow does not know that the prototype
-   and ReactElement checks preserve the type refinement of `value`. */
-function isPlainObject(value: mixed): value is $ReadOnly<{[string]: mixed}> {
+export function isPlainObject(
+  value: mixed,
+  /* $FlowIssue[incompatible-type-guard] - Flow does not know that the prototype
+     and ReactElement checks preserve the type refinement of `value`. */
+): value is $ReadOnly<{[string]: mixed}> {
   return (
     value !== null &&
     typeof value === 'object' &&
@@ -109,6 +111,14 @@ export default class AnimatedObject extends AnimatedWithChildren {
     });
   }
 
+  __getValueWithStaticObject(staticObject: mixed): any {
+    const nodes = this.#nodes;
+    let index = 0;
+    // NOTE: We can depend on `this._value` and `staticObject` sharing a
+    // structure because of `useAnimatedPropsMemo`.
+    return mapAnimatedNodes(staticObject, () => nodes[index++].__getValue());
+  }
+
   __getAnimatedValue(): any {
     return mapAnimatedNodes(this._value, node => {
       return node.__getAnimatedValue();

packages/react-native/Libraries/Animated/nodes/AnimatedProps.js

@@ -113,6 +113,31 @@ export default class AnimatedProps extends AnimatedNode {
     return props;
   }
 
+  /**
+   * Creates a new `props` object that contains the same props as the supplied
+   * `staticProps` object, except with animated nodes for any props that were
+   * created by this `AnimatedProps` instance.
+   */
+  __getValueWithStaticProps(staticProps: Object): Object {
+    const props: {[string]: mixed} = {...staticProps};
+
+    const keys = Object.keys(staticProps);
+    for (let ii = 0, length = keys.length; ii < length; ii++) {
+      const key = keys[ii];
+      const maybeNode = this.#props[key];
+
+      if (key === 'style' && maybeNode instanceof AnimatedStyle) {
+        props[key] = maybeNode.__getValueWithStaticStyle(staticProps.style);
+      } else if (maybeNode instanceof AnimatedNode) {
+        props[key] = maybeNode.__getValue();
+      } else if (maybeNode instanceof AnimatedEvent) {
+        props[key] = maybeNode.__getHandler();
+      }
+    }
+
+    return props;
+  }
+
   __getAnimatedValue(): Object {
     const props: {[string]: mixed} = {};
 

packages/react-native/Libraries/Animated/nodes/AnimatedStyle.js

@@ -138,6 +138,43 @@ export default class AnimatedStyle extends AnimatedWithChildren {
     return Platform.OS === 'web' ? [this.#inputStyle, style] : style;
   }
 
+  /**
+   * Creates a new `style` object that contains the same style properties as
+   * the supplied `staticStyle` object, except with animated nodes for any
+   * style properties that were created by this `AnimatedStyle` instance.
+   */
+  __getValueWithStaticStyle(staticStyle: Object): Object | Array<Object> {
+    const flatStaticStyle = flattenStyle(staticStyle);
+    const style: {[string]: mixed} =
+      flatStaticStyle == null
+        ? {}
+        : flatStaticStyle === staticStyle
+          ? // Copy the input style, since we'll mutate it below.
+            {...flatStaticStyle}
+          : // Reuse `flatStaticStyle` if it is a newly created object.
+            flatStaticStyle;
+
+    const keys = Object.keys(style);
+    for (let ii = 0, length = keys.length; ii < length; ii++) {
+      const key = keys[ii];
+      const maybeNode = this.#style[key];
+
+      if (key === 'transform' && maybeNode instanceof AnimatedTransform) {
+        style[key] = maybeNode.__getValueWithStaticTransforms(
+          // NOTE: This check should not be necessary, but the types are not
+          // enforced as of this writing.
+          Array.isArray(style[key]) ? style[key] : [],
+        );
+      } else if (maybeNode instanceof AnimatedObject) {
+        style[key] = maybeNode.__getValueWithStaticObject(style[key]);
+      } else if (maybeNode instanceof AnimatedNode) {
+        style[key] = maybeNode.__getValue();
+      }
+    }
+
+    return Platform.OS === 'web' ? [this.#inputStyle, style] : style;
+  }
+
   __getAnimatedValue(): Object {
     const style: {[string]: mixed} = {};
 

packages/react-native/Libraries/Animated/nodes/AnimatedTransform.js

@@ -91,6 +91,18 @@ export default class AnimatedTransform extends AnimatedWithChildren {
     );
   }
 
+  __getValueWithStaticTransforms(
+    staticTransforms: $ReadOnlyArray<Object>,
+  ): $ReadOnlyArray<Object> {
+    const values = [];
+    mapTransforms(this._transforms, node => {
+      values.push(node.__getValue());
+    });
+    // NOTE: We can depend on `this._transforms` and `staticTransforms` sharing
+    // a structure because of `useAnimatedPropsMemo`.
+    return mapTransforms(staticTransforms, () => values.shift());
+  }
+
   __getAnimatedValue(): $ReadOnlyArray<Transform<any>> {
     return mapTransforms(this._transforms, animatedNode =>
       animatedNode.__getAnimatedValue(),

packages/react-native/Libraries/Animated/useAnimatedProps.js

@@ -28,6 +28,7 @@ import {
   useReducer,
   useRef,
 } from 'react';
+import {useAnimatedPropsMemo} from '../../src/private/animated/useAnimatedPropsMemo';
 
 type ReducedProps<TProps> = {
   ...TProps,
@@ -41,23 +42,24 @@ type AnimatedValueListeners = Array<{
   listenerId: string,
 }>;
 
+const useMemoOrAnimatedPropsMemo =
+  ReactNativeFeatureFlags.enableAnimatedPropsMemo()
+    ? useAnimatedPropsMemo
+    : useMemo;
+
 export default function useAnimatedProps<TProps: {...}, TInstance>(
   props: TProps,
   allowlist?: ?AnimatedPropsAllowlist,
 ): [ReducedProps<TProps>, CallbackRef<TInstance | null>] {
   const [, scheduleUpdate] = useReducer<number, void>(count => count + 1, 0);
-  const onUpdateRef = useRef<?() => void>(null);
+  const onUpdateRef = useRef<(() => void) | null>(null);
   const timerRef = useRef<TimeoutID | null>(null);
 
   const allowlistIfEnabled = ReactNativeFeatureFlags.enableAnimatedAllowlist()
     ? allowlist
     : null;
 
-  // TODO: Only invalidate `node` if animated props or `style` change. In the
-  // previous implementation, we permitted `style` to override props with the
-  // same name property name as styles, so we can probably continue doing that.
-  // The ordering of other props *should* not matter.
-  const node = useMemo(
+  const node = useMemoOrAnimatedPropsMemo(
     () =>
       new AnimatedProps(
         props,
@@ -66,6 +68,7 @@ export default function useAnimatedProps<TProps: {...}, TInstance>(
       ),
     [allowlistIfEnabled, props],
   );
+
   const useNativePropsInFabric =
     ReactNativeFeatureFlags.shouldUseSetNativePropsInFabric();
   const useSetNativePropsInNativeAnimationsInFabric =
@@ -205,14 +208,19 @@ export default function useAnimatedProps<TProps: {...}, TInstance>(
   );
   const callbackRef = useRefEffect<TInstance>(refEffect);
 
-  return [reduceAnimatedProps<TProps>(node), callbackRef];
+  return [reduceAnimatedProps<TProps>(node, props), callbackRef];
 }
 
-function reduceAnimatedProps<TProps>(node: AnimatedNode): ReducedProps<TProps> {
+function reduceAnimatedProps<TProps>(
+  node: AnimatedProps,
+  props: TProps,
+): ReducedProps<TProps> {
   // Force `collapsable` to be false so that the native view is not flattened.
   // Flattened views cannot be accurately referenced by the native driver.
   return {
-    ...node.__getValue(),
+    ...(ReactNativeFeatureFlags.enableAnimatedPropsMemo()
+      ? node.__getValueWithStaticProps(props)
+      : node.__getValue()),
     collapsable: false,
   };
 }

packages/react-native/Libraries/__tests__/__snapshots__/public-api-test.js.snap

@@ -938,11 +938,15 @@ exports[`public API should not change unintentionally Libraries/Animated/nodes/A
 `;
 
 exports[`public API should not change unintentionally Libraries/Animated/nodes/AnimatedObject.js 1`] = `
-"declare export default class AnimatedObject extends AnimatedWithChildren {
+"declare export function isPlainObject(
+  value: mixed
+): value is $ReadOnly<{ [string]: mixed }>;
+declare export default class AnimatedObject extends AnimatedWithChildren {
   _value: mixed;
   static from(value: mixed): ?AnimatedObject;
   constructor(nodes: $ReadOnlyArray<AnimatedNode>, value: mixed): void;
   __getValue(): any;
+  __getValueWithStaticObject(staticObject: mixed): any;
   __getAnimatedValue(): any;
   __attach(): void;
   __detach(): void;
@@ -964,6 +968,7 @@ declare export default class AnimatedProps extends AnimatedNode {
     allowlist?: ?AnimatedPropsAllowlist
   ): void;
   __getValue(): Object;
+  __getValueWithStaticProps(staticProps: Object): Object;
   __getAnimatedValue(): Object;
   __attach(): void;
   __detach(): void;
@@ -992,6 +997,7 @@ declare export default class AnimatedStyle extends AnimatedWithChildren {
     inputStyle: any
   ): void;
   __getValue(): Object | Array<Object>;
+  __getValueWithStaticStyle(staticStyle: Object): Object | Array<Object>;
   __getAnimatedValue(): Object;
   __attach(): void;
   __detach(): void;
@@ -1061,6 +1067,9 @@ declare export default class AnimatedTransform extends AnimatedWithChildren {
   ): void;
   __makeNative(platformConfig: ?PlatformConfig): void;
   __getValue(): $ReadOnlyArray<Transform<any>>;
+  __getValueWithStaticTransforms(
+    staticTransforms: $ReadOnlyArray<Object>
+  ): $ReadOnlyArray<Object>;
   __getAnimatedValue(): $ReadOnlyArray<Transform<any>>;
   __attach(): void;
   __detach(): void;

packages/react-native/scripts/featureflags/ReactNativeFeatureFlags.config.js

@@ -298,6 +298,11 @@ const definitions: FeatureFlagDefinitions = {
       defaultValue: false,
       description: 'Enables Animated to skip non-allowlisted props and styles.',
     },
+    enableAnimatedPropsMemo: {
+      defaultValue: false,
+      description:
+        'Enables Animated to analyze props to minimize invalidating `AnimatedProps`.',
+    },
     enableOptimisedVirtualizedCells: {
       defaultValue: false,
       description: