facebook/flow v0.232.0

on GitHub

Likely to cause new Flow errors:

• Support for $Compose and $ComposeReverse types are removed. We recommend to use overloads to approximate their behavior instead. e.g.

declare export function compose(): <T>(a: T) => T;
declare export function compose<F: (...$ReadOnlyArray<empty>) => mixed>(
  f: F,
): F;
declare export function compose<A, T: $ReadOnlyArray<any>, R>(
  f1: (a: A) => R,
  f2: (...T) => A,
): (...T) => R;
declare export function compose<A, B, T: $ReadOnlyArray<any>, R>(
  f1: (b: B) => R,
  f2: (a: A) => B,
  f3: (...T) => A,
): (...T) => R;
declare export function compose<A, B, C, T: $ReadOnlyArray<any>, R>(
  f1: (c: C) => R,
  f2: (b: B) => C,
  f3: (a: A) => B,
  f4: (...T) => A,
): (...T) => R;
declare export function compose<R>(
  f1: (b: any) => R,
  ...funcs: $ReadOnlyArray<(...$ReadOnlyArray<empty>) => mixed>
): (...$ReadOnlyArray<any>) => R;
declare export function compose<R>(
  ...funcs: $ReadOnlyArray<(...$ReadOnlyArray<empty>) => mixed>
): (...$ReadOnlyArray<any>) => R;

• You might see more errors around type application. example
• Fix subtyping of indexers in instances/interfaces. example

New Features:

• Updated the isValid Flow Enums method to use a type guard, allowing it to refine its input to the enum type in a conditional context.
  E.g.

enum Status {Active, Off}
const s = "Active";
if (Status.isValid(s)) {
  s as Status; // Should work
}

• export type Foo = ... and export interface Bar {...} statements are now allowed in declare module and declare namespace bodies.
• We added a new codemod flow codemod remove-unnecessary-react-import which can help remove unnecessary react imports under react.runtime=automatic

Notable bug fixes:

• Fixed issue when explicitly supplied JSX type arguments are ignored
• Fixed code action output of casting syntax when LHS of as or as const has low precedence

Library Definitions:

• Added definitions for the following APIs:
  • window.showOpenFilePicker(): MDN, WICG
  • window.showSaveFilePicker(): MDN, WICG
  • window.showDirectoryPicker(): MDN, WICG
  • DataTransferItem.getAsFileSystemHandle(): MDN, WICG
  • StorageManager.getDirectory(): MDN, WHATWG