Align StyleSheet Flow with TS types

packages/react-native/Libraries/StyleSheet/StyleSheet.js

@@ -10,25 +10,21 @@
 
 'use strict';
 
+import typeof * as StyleSheetExports from './StyleSheetExports';
 import type {
   ____ColorValue_Internal,
   ____DangerouslyImpreciseStyle_Internal,
   ____DangerouslyImpreciseStyleProp_Internal,
   ____ImageStyle_Internal,
   ____ImageStyleProp_Internal,
-  ____Styles_Internal,
   ____TextStyle_Internal,
   ____TextStyleProp_Internal,
   ____ViewStyle_Internal,
   ____ViewStyleProp_Internal,
 } from './StyleSheetTypes';
-
-import composeStyles from '../../src/private/styles/composeStyles';
-import flatten from './flattenStyle';
-
-const ReactNativeStyleAttributes =
-  require('../Components/View/ReactNativeStyleAttributes').default;
-const PixelRatio = require('../Utilities/PixelRatio').default;
+const StyleSheet: StyleSheetExports = (
+  require('./StyleSheetExports') as $FlowFixMe
+).default;
 
 export type {NativeColorValue} from './StyleSheetTypes';
 
@@ -166,192 +162,4 @@ export type ImageStyle = ____ImageStyle_Internal;
  */
 export type DangerouslyImpreciseStyle = ____DangerouslyImpreciseStyle_Internal;
 
-let hairlineWidth: number = PixelRatio.roundToNearestPixel(0.4);
-if (hairlineWidth === 0) {
-  hairlineWidth = 1 / PixelRatio.get();
-}
-
-const absoluteFill: {
-  +bottom: 0,
-  +left: 0,
-  +position: 'absolute',
-  +right: 0,
-  +top: 0,
-} = {
-  position: 'absolute',
-  left: 0,
-  right: 0,
-  top: 0,
-  bottom: 0,
-};
-if (__DEV__) {
-  Object.freeze(absoluteFill);
-}
-
-/**
- * A StyleSheet is an abstraction similar to CSS StyleSheets
- *
- * Create a new StyleSheet:
- *
- * ```
- * const styles = StyleSheet.create({
- *   container: {
- *     borderRadius: 4,
- *     borderWidth: 0.5,
- *     borderColor: '#d6d7da',
- *   },
- *   title: {
- *     fontSize: 19,
- *     fontWeight: 'bold',
- *   },
- *   activeTitle: {
- *     color: 'red',
- *   },
- * });
- * ```
- *
- * Use a StyleSheet:
- *
- * ```
- * <View style={styles.container}>
- *   <Text style={[styles.title, this.props.isActive && styles.activeTitle]} />
- * </View>
- * ```
- *
- * Code quality:
- *
- *  - By moving styles away from the render function, you're making the code
- *    easier to understand.
- *  - Naming the styles is a good way to add meaning to the low level components
- *  in the render function, and encourage reuse.
- *  - In most IDEs, using `StyleSheet.create()` will offer static type checking
- *  and suggestions to help you write valid styles.
- *
- */
-export default {
-  /**
-   * This is defined as the width of a thin line on the platform. It can be
-   * used as the thickness of a border or division between two elements.
-   * Example:
-   * ```
-   *   {
-   *     borderBottomColor: '#bbb',
-   *     borderBottomWidth: StyleSheet.hairlineWidth
-   *   }
-   * ```
-   *
-   * This constant will always be a round number of pixels (so a line defined
-   * by it look crisp) and will try to match the standard width of a thin line
-   * on the underlying platform. However, you should not rely on it being a
-   * constant size, because on different platforms and screen densities its
-   * value may be calculated differently.
-   *
-   * A line with hairline width may not be visible if your simulator is downscaled.
-   */
-  hairlineWidth,
-
-  /**
-   * A very common pattern is to create overlays with position absolute and zero positioning,
-   * so `absoluteFill` can be used for convenience and to reduce duplication of these repeated
-   * styles.
-   */
-  absoluteFill: (absoluteFill: any), // TODO: This should be updated after we fix downstream Flow sites.
-
-  /**
-   * Sometimes you may want `absoluteFill` but with a couple tweaks - `absoluteFillObject` can be
-   * used to create a customized entry in a `StyleSheet`, e.g.:
-   *
-   *   const styles = StyleSheet.create({
-   *     wrapper: {
-   *       ...StyleSheet.absoluteFillObject,
-   *       top: 10,
-   *       backgroundColor: 'transparent',
-   *     },
-   *   });
-   */
-  absoluteFillObject: absoluteFill,
-
-  /**
-   * Combines two styles such that `style2` will override any styles in `style1`.
-   * If either style is falsy, the other one is returned without allocating an
-   * array, saving allocations and maintaining reference equality for
-   * PureComponent checks.
-   */
-  compose: composeStyles,
-
-  /**
-   * Flattens an array of style objects, into one aggregated style object.
-   *
-   * Example:
-   * ```
-   * const styles = StyleSheet.create({
-   *   listItem: {
-   *     flex: 1,
-   *     fontSize: 16,
-   *     color: 'white'
-   *   },
-   *   selectedListItem: {
-   *     color: 'green'
-   *   }
-   * });
-   *
-   * StyleSheet.flatten([styles.listItem, styles.selectedListItem])
-   * // returns { flex: 1, fontSize: 16, color: 'green' }
-   * ```
-   */
-  flatten,
-
-  /**
-   * WARNING: EXPERIMENTAL. Breaking changes will probably happen a lot and will
-   * not be reliably announced. The whole thing might be deleted, who knows? Use
-   * at your own risk.
-   *
-   * Sets a function to use to pre-process a style property value. This is used
-   * internally to process color and transform values. You should not use this
-   * unless you really know what you are doing and have exhausted other options.
-   */
-  setStyleAttributePreprocessor(
-    property: string,
-    process: (nextProp: mixed) => mixed,
-  ) {
-    let value;
-
-    if (ReactNativeStyleAttributes[property] === true) {
-      value = {process};
-    } else if (typeof ReactNativeStyleAttributes[property] === 'object') {
-      value = {...ReactNativeStyleAttributes[property], process};
-    } else {
-      console.error(`${property} is not a valid style attribute`);
-      return;
-    }
-
-    if (
-      __DEV__ &&
-      typeof value.process === 'function' &&
-      typeof ReactNativeStyleAttributes[property]?.process === 'function' &&
-      value.process !== ReactNativeStyleAttributes[property]?.process
-    ) {
-      console.warn(`Overwriting ${property} style attribute preprocessor`);
-    }
-
-    ReactNativeStyleAttributes[property] = value;
-  },
-
-  /**
-   * An identity function for creating style sheets.
-   */
-  // $FlowFixMe[unsupported-variance-annotation]
-  create<+S: ____Styles_Internal>(obj: S): $ReadOnly<S> {
-    // TODO: This should return S as the return type. But first,
-    // we need to codemod all the callsites that are typing this
-    // return value as a number (even though it was opaque).
-    if (__DEV__) {
-      for (const key in obj) {
-        if (obj[key]) {
-          Object.freeze(obj[key]);
-        }
-      }
-    }
-    return obj;
-  },
-};
+export default StyleSheet;

packages/react-native/Libraries/StyleSheet/StyleSheet.js.flow

@@ -0,0 +1,166 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+export * as default from './StyleSheetExports';
+
+import type {
+  ____ColorValue_Internal,
+  ____DangerouslyImpreciseStyle_Internal,
+  ____DangerouslyImpreciseStyleProp_Internal,
+  ____ImageStyle_Internal,
+  ____ImageStyleProp_Internal,
+  ____TextStyle_Internal,
+  ____TextStyleProp_Internal,
+  ____ViewStyle_Internal,
+  ____ViewStyleProp_Internal,
+} from './StyleSheetTypes';
+
+export type {StyleProp} from './StyleSheetTypes';
+
+export type StyleSheetProperties = {
+  hairlineWidth: number,
+  flatten<T: string>(style: T): T,
+};
+
+export type {NativeColorValue} from './StyleSheetTypes';
+
+/**
+ * This type should be used as the type for anything that is a color. It is
+ * most useful when using DynamicColorIOS which can be a string or a dynamic
+ * color object.
+ *
+ * type props = {backgroundColor: ColorValue};
+ */
+export type ColorValue = ____ColorValue_Internal;
+
+/**
+ * This type should be used as the type for a prop that is passed through
+ * to a <View>'s `style` prop. This ensures call sites of the component
+ * can't pass styles that View doesn't support such as `fontSize`.`
+ *
+ * type Props = {style: ViewStyleProp}
+ * const MyComponent = (props: Props) => <View style={props.style} />
+ */
+export type ViewStyleProp = ____ViewStyleProp_Internal;
+
+/**
+ * This type should be used as the type for a prop that is passed through
+ * to a <Text>'s `style` prop. This ensures call sites of the component
+ * can't pass styles that Text doesn't support such as `resizeMode`.`
+ *
+ * type Props = {style: TextStyleProp}
+ * const MyComponent = (props: Props) => <Text style={props.style} />
+ */
+export type TextStyleProp = ____TextStyleProp_Internal;
+
+/**
+ * This type should be used as the type for a prop that is passed through
+ * to an <Image>'s `style` prop. This ensures call sites of the component
+ * can't pass styles that Image doesn't support such as `fontSize`.`
+ *
+ * type Props = {style: ImageStyleProp}
+ * const MyComponent = (props: Props) => <Image style={props.style} />
+ */
+export type ImageStyleProp = ____ImageStyleProp_Internal;
+
+/**
+ * WARNING: You probably shouldn't be using this type. This type
+ * is similar to the ones above except it allows styles that are accepted
+ * by all of View, Text, or Image. It is therefore very unsafe to pass this
+ * through to an underlying component. Using this is almost always a mistake
+ * and using one of the other more restrictive types is likely the right choice.
+ */
+export type DangerouslyImpreciseStyleProp =
+  ____DangerouslyImpreciseStyleProp_Internal;
+
+/**
+ * Utility type for getting the values for specific style keys.
+ *
+ * The following is bad because position is more restrictive than 'string':
+ * ```
+ * type Props = {position: string};
+ * ```
+ *
+ * You should use the following instead:
+ *
+ * ```
+ * type Props = {position: TypeForStyleKey<'position'>};
+ * ```
+ *
+ * This will correctly give you the type 'absolute' | 'relative'
+ */
+export type TypeForStyleKey<
+  +key: $Keys<____DangerouslyImpreciseStyle_Internal>,
+> = $ElementType<____DangerouslyImpreciseStyle_Internal, key>;
+
+/**
+ * This type is an object of the different possible style
+ * properties that can be specified for View.
+ *
+ * Note that this isn't a safe way to type a style prop for a component as
+ * results from StyleSheet.create return an internal identifier, not
+ * an object of styles.
+ *
+ * If you want to type the style prop of a function,
+ * consider using ViewStyleProp.
+ *
+ * A reasonable usage of this type is for helper functions that return an
+ * object of styles to pass to a View that can't be precomputed with
+ * StyleSheet.create.
+ */
+export type ViewStyle = ____ViewStyle_Internal;
+
+/**
+ * This type is an object of the different possible style
+ * properties that can be specified for Text.
+ *
+ * Note that this isn't a safe way to type a style prop for a component as
+ * results from StyleSheet.create return an internal identifier, not
+ * an object of styles.
+ *
+ * If you want to type the style prop of a function,
+ * consider using TextStyleProp.
+ *
+ * A reasonable usage of this type is for helper functions that return an
+ * object of styles to pass to a Text that can't be precomputed with
+ * StyleSheet.create.
+ */
+export type TextStyle = ____TextStyle_Internal;
+
+/**
+ * This type is an object of the different possible style
+ * properties that can be specified for Image.
+ *
+ * Note that this isn't a safe way to type a style prop for a component as
+ * results from StyleSheet.create return an internal identifier, not
+ * an object of styles.
+ *
+ * If you want to type the style prop of a function,
+ * consider using ImageStyleProp.
+ *
+ * A reasonable usage of this type is for helper functions that return an
+ * object of styles to pass to an Image that can't be precomputed with
+ * StyleSheet.create.
+ */
+export type ImageStyle = ____ImageStyle_Internal;
+
+/**
+ * WARNING: You probably shouldn't be using this type. This type is an object
+ * with all possible style keys and their values. Note that this isn't
+ * a safe way to type a style prop for a component as results from
+ * StyleSheet.create return an internal identifier, not an object of styles.
+ *
+ * If you want to type the style prop of a function, consider using
+ * ViewStyleProp, TextStyleProp, or ImageStyleProp.
+ *
+ * This should only be used by very core utilities that operate on an object
+ * containing any possible style value.
+ */
+export type DangerouslyImpreciseStyle = ____DangerouslyImpreciseStyle_Internal;