[change] modernize ImageBackground

Rewrite ImageBackground to use function components and hooks.
Rewrite the tests to replace enzyme with testing-library.

packages/react-native-web/src/exports/ImageBackground/__tests__/index.js

@@ -1,36 +1,39 @@
 /* eslint-env jasmine, jest */
 
-import Image from '../../Image';
 import ImageBackground from '..';
 import React from 'react';
-import { shallow } from 'enzyme';
+import { render } from '@testing-library/react';
 import Text from '../../Text';
 
+function findImage(container) {
+  return container.firstChild.firstChild;
+}
+
 describe('components/ImageBackground', () => {
   describe('prop "children"', () => {
-    it('render child content', () => {
-      const component = shallow(
+    test('render child content', () => {
+      const { getByText } = render(
         <ImageBackground>
           <Text>Hello World!</Text>
         </ImageBackground>
       );
-      expect(component.find(Text)).toBeDefined();
+      expect(getByText('Hello World!')).toBeDefined();
     });
   });
 
   describe('prop "imageStyle"', () => {
-    it('sets the style of the underlying Image', () => {
+    test('sets the style of the underlying Image', () => {
       const imageStyle = { width: 40, height: 60 };
-      const component = shallow(<ImageBackground imageStyle={imageStyle} />);
-      expect(component.find(Image).prop('style')).toContain(imageStyle);
+      const { container } = render(<ImageBackground imageStyle={imageStyle} />);
+      expect(findImage(container).getAttribute('style')).toBe('height: 60px; width: 40px;');
     });
   });
 
   describe('prop "style"', () => {
-    it('sets the style of the container View', () => {
+    test('sets the style of the container View', () => {
       const style = { margin: 40 };
-      const component = shallow(<ImageBackground style={style} />);
-      expect(component.prop('style')).toEqual(style);
+      const { container } = render(<ImageBackground style={style} />);
+      expect(container.firstChild.getAttribute('style')).toEqual('margin: 40px 40px 40px 40px;');
     });
   });
 });

packages/react-native-web/src/exports/ImageBackground/index.js

@@ -10,11 +10,11 @@
 import type { ImageProps } from '../Image';
 import type { ViewProps } from '../View';
 
-import ensureComponentIsNative from '../../modules/ensureComponentIsNative';
+import setAndForwardRef from '../../modules/setAndForwardRef';
 import Image from '../Image';
 import StyleSheet from '../StyleSheet';
 import View from '../View';
-import React from 'react';
+import React, { forwardRef, useImperativeHandle, useRef } from 'react';
 
 type ImageBackgroundProps = {
   ...ImageProps,
@@ -28,52 +28,58 @@ const emptyObject = {};
 /**
  * Very simple drop-in replacement for <Image> which supports nesting views.
  */
-class ImageBackground extends React.Component<ImageBackgroundProps> {
-  setNativeProps(props: Object) {
-    // Work-around flow
-    const viewRef = this._viewRef;
-    if (viewRef) {
-      ensureComponentIsNative(viewRef);
-      viewRef.setNativeProps(props);
+const ImageBackground = forwardRef<ImageBackgroundProps, *>((props, ref) => {
+  const { children, style = emptyObject, imageStyle, imageRef, ...rest } = props;
+  const { height, width } = StyleSheet.flatten(style);
+
+  const containerRef = useRef(null);
+
+  useImperativeHandle(
+    ref,
+    () => ({
+      setNativeProps(props) {
+        if (containerRef.current != null) {
+          containerRef.current.setNativeProps(props);
+        }
+      }
+    }),
+    [containerRef]
+  );
+
+  const setRef = setAndForwardRef({
+    getForwardedRef: () => ref,
+    setLocalRef: c => {
+      containerRef.current = c;
     }
-  }
+  });
 
-  _viewRef: ?View = null;
+  return (
+    <View ref={setRef} style={style}>
+      <Image
+        {...rest}
+        ref={imageRef}
+        style={[
+          StyleSheet.absoluteFill,
+          {
+            // Temporary Workaround:
+            // Current (imperfect yet) implementation of <Image> overwrites width and height styles
+            // (which is not quite correct), and these styles conflict with explicitly set styles
+            // of <ImageBackground> and with our internal layout model here.
+            // So, we have to proxy/reapply these styles explicitly for actual <Image> component.
+            // This workaround should be removed after implementing proper support of
+            // intrinsic content size of the <Image>.
+            width,
+            height,
+            zIndex: -1
+          },
+          imageStyle
+        ]}
+      />
+      {children}
+    </View>
+  );
+});
 
-  _captureRef = (ref: View) => {
-    this._viewRef = ref;
-  };
-
-  render() {
-    const { children, style = emptyObject, imageStyle, imageRef, ...props } = this.props;
-    const { height, width } = StyleSheet.flatten(style);
-
-    return (
-      <View ref={this._captureRef} style={style}>
-        <Image
-          {...props}
-          ref={imageRef}
-          style={[
-            StyleSheet.absoluteFill,
-            {
-              // Temporary Workaround:
-              // Current (imperfect yet) implementation of <Image> overwrites width and height styles
-              // (which is not quite correct), and these styles conflict with explicitly set styles
-              // of <ImageBackground> and with our internal layout model here.
-              // So, we have to proxy/reapply these styles explicitly for actual <Image> component.
-              // This workaround should be removed after implementing proper support of
-              // intrinsic content size of the <Image>.
-              width,
-              height,
-              zIndex: -1
-            },
-            imageStyle
-          ]}
-        />
-        {children}
-      </View>
-    );
-  }
-}
+ImageBackground.displayName = 'ImageBackground';
 
 export default ImageBackground;

packages/react-native-web/src/modules/setAndForwardRef/index.js

@@ -0,0 +1,58 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ */
+
+import * as React from 'react';
+
+type Args = $ReadOnly<{|
+  getForwardedRef: () => ?React.Ref<any>,
+  setLocalRef: (ref: React.ElementRef<any>) => mixed
+|}>;
+
+/**
+ * This is a helper function for when a component needs to be able to forward a ref
+ * to a child component, but still needs to have access to that component as part of
+ * its implementation.
+ *
+ * Its main use case is in wrappers for native components.
+ *
+ * Usage:
+ *
+ *   function MyView(props) {
+ *     const ref = useRef(null);
+ *
+ *     function setRef = setAndForwardRef({
+ *       getForwardedRef: () => props.forwardedRef,
+ *       setLocalRef: localRef => {
+ *         ref.current = localRef;
+ *       },
+ *     });
+ *
+ *     return <View ref={setRef} />;
+ *   }
+ *
+ *   const MyViewWithRef = React.forwardRef((props, ref) => (
+ *     <MyView {...props} forwardedRef={ref} />
+ *   ));
+ */
+
+export default function setAndForwardRef({ getForwardedRef, setLocalRef }: Args) {
+  return function forwardRef(ref: React.ElementRef<any>) {
+    const forwardedRef = getForwardedRef();
+    setLocalRef(ref);
+
+    // Forward to user ref prop (if one has been specified)
+    if (typeof forwardedRef === 'function') {
+      // Handle function-based refs. String-based refs are handled as functions.
+      forwardedRef(ref);
+    } else if (typeof forwardedRef === 'object' && forwardedRef != null) {
+      // Handle createRef-based refs
+      forwardedRef.current = ref;
+    }
+  };
+}