fix(types): Switching Promise to PromiseLike (#1850 by @kav)

packages/mobx-state-tree/__tests__/core/async.test.ts

@@ -1,18 +1,18 @@
+import { configure, reaction } from "mobx"
 import {
-    types,
     addMiddleware,
-    recordActions,
-    flow,
     decorate,
     destroy,
-    IMiddlewareHandler,
+    flow,
     IMiddlewareEvent,
     IMiddlewareEventType,
-    toGeneratorFunction,
-    toGenerator
+    IMiddlewareHandler,
+    recordActions,
+    toGenerator,
     // TODO: export IRawActionCall
+    toGeneratorFunction,
+    types
 } from "../../src"
-import { reaction, configure } from "mobx"
 
 function delay<TV>(time: number, value: TV, shouldThrow = false): Promise<TV> {
     return new Promise((resolve, reject) => {
@@ -27,7 +27,7 @@ function testCoffeeTodo(
     done: () => void,
     generator: (
         self: any
-    ) => (str: string) => Generator<Promise<any>, string | void | undefined, undefined>,
+    ) => (str: string) => Generator<PromiseLike<any>, string | void | undefined, undefined>,
     shouldError: boolean,
     resultValue: string | undefined,
     producedCoffees: any[]

packages/mobx-state-tree/src/core/flow.ts

@@ -1,25 +1,25 @@
+import { argsToArray, fail, setImmediateWithFallback } from "../utils"
 import {
     getCurrentActionContext,
     getNextActionId,
     getParentActionContext,
     IMiddlewareEventType,
     runWithActionContext
 } from "./action"
-import { argsToArray, setImmediateWithFallback, fail } from "../utils"
 
 /**
  * @hidden
  */
-export type FlowReturn<R> = R extends Promise<infer T> ? T : R
+export type FlowReturn<R> = R extends PromiseLike<infer T> ? T : R
 
 /**
  * See [asynchronous actions](concepts/async-actions.md).
  *
  * @returns The flow as a promise.
  */
 export function flow<R, Args extends any[]>(
-    generator: (...args: Args) => Generator<Promise<any>, R, any>
-): (...args: Args) => Promise<FlowReturn<R>> {
+    generator: (...args: Args) => Generator<PromiseLike<any>, R, any>
+): (...args: Args) => PromiseLike<FlowReturn<R>> {
     return createFlowSpawner(generator.name, generator) as any
 }
 
@@ -56,7 +56,7 @@ export function castFlowReturn<T>(val: T): T {
  * }))
  * ```
  */
-export function toGeneratorFunction<R, Args extends any[]>(p: (...args: Args) => Promise<R>) {
+export function toGeneratorFunction<R, Args extends any[]>(p: (...args: Args) => PromiseLike<R>) {
     return function* (...args: Args) {
         return (yield p(...args)) as R
     }