refactor: simplify native state management (#1662)

* refactor: improve native state management

* feat: add fireEvent.scroll support for scroll native events

Author: mdjastrzebski

src/cleanup.ts

@@ -1,12 +1,10 @@
-import { clearNativeState } from './native-state';
 import { clearRenderResult } from './screen';
 
 type CleanUpFunction = () => void;
 
 const cleanupQueue = new Set<CleanUpFunction>();
 
 export default function cleanup() {
-  clearNativeState();
   clearRenderResult();
 
   cleanupQueue.forEach((fn) => fn());

src/fire-event.ts

@@ -8,10 +8,10 @@ import {
 } from 'react-native';
 import act from './act';
 import { isHostElement } from './helpers/component-tree';
-import { isHostTextInput } from './helpers/host-component-names';
+import { isHostScrollView, isHostTextInput } from './helpers/host-component-names';
 import { isPointerEventEnabled } from './helpers/pointer-events';
 import { isTextInputEditable } from './helpers/text-input';
-import { StringWithAutocomplete } from './types';
+import { Point, StringWithAutocomplete } from './types';
 import { nativeState } from './native-state';
 
 type EventHandler = (...args: unknown[]) => unknown;
@@ -147,13 +147,47 @@ fireEvent.scroll = (element: ReactTestInstance, ...data: unknown[]) =>
 
 export default fireEvent;
 
+const scrollEventNames = new Set([
+  'scroll',
+  'scrollBeginDrag',
+  'scrollEndDrag',
+  'momentumScrollBegin',
+  'momentumScrollEnd',
+]);
+
 function setNativeStateIfNeeded(element: ReactTestInstance, eventName: string, value: unknown) {
   if (
     eventName === 'changeText' &&
     typeof value === 'string' &&
     isHostTextInput(element) &&
     isTextInputEditable(element)
   ) {
-    nativeState?.valueForElement.set(element, value);
+    nativeState.valueForElement.set(element, value);
+  }
+
+  if (scrollEventNames.has(eventName) && isHostScrollView(element)) {
+    const contentOffset = tryGetContentOffset(value);
+    if (contentOffset) {
+      nativeState.contentOffsetForElement.set(element, contentOffset);
+    }
   }
 }
+
+function tryGetContentOffset(value: unknown): Point | null {
+  try {
+    // @ts-expect-error: try to extract contentOffset from the event value
+    const contentOffset = value?.nativeEvent?.contentOffset;
+    const x = contentOffset?.x;
+    const y = contentOffset?.y;
+    if (typeof x === 'number' || typeof y === 'number') {
+      return {
+        x: Number.isFinite(x) ? x : 0,
+        y: Number.isFinite(y) ? y : 0,
+      };
+    }
+  } catch {
+    // Do nothing
+  }
+
+  return null;
+}

src/helpers/matchers/match-label-text.ts

@@ -18,10 +18,10 @@ export function matchLabelText(
 
 function matchAccessibilityLabel(
   element: ReactTestInstance,
-  extpectedLabel: TextMatch,
+  expectedLabel: TextMatch,
   options: TextMatchOptions,
 ) {
-  return matches(extpectedLabel, computeAriaLabel(element), options.normalizer, options.exact);
+  return matches(expectedLabel, computeAriaLabel(element), options.normalizer, options.exact);
 }
 
 function matchAccessibilityLabelledBy(

src/helpers/text-input.ts

@@ -17,7 +17,7 @@ export function getTextInputValue(element: ReactTestInstance) {
 
   return (
     element.props.value ??
-    nativeState?.valueForElement.get(element) ??
+    nativeState.valueForElement.get(element) ??
     element.props.defaultValue ??
     ''
   );

src/native-state.ts

@@ -11,15 +11,7 @@ export type NativeState = {
   contentOffsetForElement: WeakMap<ReactTestInstance, Point>;
 };
 
-export let nativeState: NativeState | null = null;
-
-export function initNativeState(): void {
-  nativeState = {
-    valueForElement: new WeakMap(),
-    contentOffsetForElement: new WeakMap(),
-  };
-}
-
-export function clearNativeState(): void {
-  nativeState = null;
-}
+export let nativeState: NativeState = {
+  valueForElement: new WeakMap(),
+  contentOffsetForElement: new WeakMap(),
+};

src/render.tsx

@@ -12,7 +12,6 @@ import { validateStringsRenderedWithinText } from './helpers/string-validation';
 import { renderWithAct } from './render-act';
 import { setRenderResult } from './screen';
 import { getQueriesForElement } from './within';
-import { initNativeState } from './native-state';
 
 export interface RenderOptions {
   wrapper?: React.ComponentType<any>;
@@ -128,7 +127,6 @@ function buildRenderResult(
   });
 
   setRenderResult(result);
-  initNativeState();
 
   return result;
 }

src/user-event/paste.ts

@@ -33,7 +33,7 @@ export async function paste(
   dispatchEvent(element, 'selectionChange', EventBuilder.TextInput.selectionChange(rangeToClear));
 
   // 3. Paste the text
-  nativeState?.valueForElement.set(element, text);
+  nativeState.valueForElement.set(element, text);
   dispatchEvent(element, 'change', EventBuilder.TextInput.change(text));
   dispatchEvent(element, 'changeText', text);
 

src/user-event/scroll/__tests__/scroll-to.test.tsx

@@ -1,7 +1,7 @@
 import * as React from 'react';
 import { ScrollView, ScrollViewProps, View } from 'react-native';
 import { EventEntry, createEventLogger } from '../../../test-utils';
-import { render, screen } from '../../..';
+import { fireEvent, render, screen } from '../../..';
 import { userEvent } from '../..';
 
 function mapEventsToShortForm(events: EventEntry[]) {
@@ -103,7 +103,7 @@ describe('scrollTo()', () => {
     ]);
   });
 
-  test('remembers previous scroll position', async () => {
+  test('remembers previous scroll offset', async () => {
     const { events } = renderScrollViewWithToolkit();
     const user = userEvent.setup();
 
@@ -123,6 +123,24 @@ describe('scrollTo()', () => {
     ]);
   });
 
+  test('remembers previous scroll offset from "fireEvent.scroll"', async () => {
+    const { events } = renderScrollViewWithToolkit();
+    const user = userEvent.setup();
+
+    fireEvent.scroll(screen.getByTestId('scrollView'), {
+      nativeEvent: { contentOffset: { y: 100 } },
+    });
+    await user.scrollTo(screen.getByTestId('scrollView'), { y: 200 });
+    expect(mapEventsToShortForm(events)).toEqual([
+      ['scroll', 100, undefined],
+      ['scrollBeginDrag', 100, 0],
+      ['scroll', 125, 0],
+      ['scroll', 150, 0],
+      ['scroll', 175, 0],
+      ['scrollEndDrag', 200, 0],
+    ]);
+  });
+
   it('validates vertical scroll direction', async () => {
     renderScrollViewWithToolkit();
     const user = userEvent.setup();

src/user-event/scroll/scroll-to.ts

@@ -56,24 +56,24 @@ export async function scrollTo(
     options.contentSize?.height ?? 0,
   );
 
-  const initialPosition = nativeState?.contentOffsetForElement.get(element) ?? { x: 0, y: 0 };
+  const initialOffset = nativeState.contentOffsetForElement.get(element) ?? { x: 0, y: 0 };
   const dragSteps = createScrollSteps(
     { y: options.y, x: options.x },
-    initialPosition,
+    initialOffset,
     linearInterpolator,
   );
   await emitDragScrollEvents(this.config, element, dragSteps, options);
 
-  const momentumStart = dragSteps.at(-1) ?? initialPosition;
+  const momentumStart = dragSteps.at(-1) ?? initialOffset;
   const momentumSteps = createScrollSteps(
     { y: options.momentumY, x: options.momentumX },
     momentumStart,
     inertialInterpolator,
   );
   await emitMomentumScrollEvents(this.config, element, momentumSteps, options);
 
-  const finalPosition = momentumSteps.at(-1) ?? dragSteps.at(-1) ?? initialPosition;
-  nativeState?.contentOffsetForElement.set(element, finalPosition);
+  const finalOffset = momentumSteps.at(-1) ?? dragSteps.at(-1) ?? initialOffset;
+  nativeState.contentOffsetForElement.set(element, finalOffset);
 }
 
 async function emitDragScrollEvents(

src/user-event/type/type.ts

@@ -95,7 +95,7 @@ export async function emitTypingEvents(
     return;
   }
 
-  nativeState?.valueForElement.set(element, text);
+  nativeState.valueForElement.set(element, text);
   dispatchEvent(element, 'change', EventBuilder.TextInput.change(text));
   dispatchEvent(element, 'changeText', text);