[pull] main from facebook:main

.eslintrc.js

@@ -593,6 +593,7 @@ module.exports = {
     mixin$Animatable: 'readonly',
     MouseEventHandler: 'readonly',
     NavigateEvent: 'readonly',
+    Partial: 'readonly',
     PerformanceMeasureOptions: 'readonly',
     PropagationPhases: 'readonly',
     PropertyDescriptor: 'readonly',

flow-typed/environments/bom.js

@@ -826,7 +826,7 @@ declare class WebSocket extends EventTarget {
   bufferedAmount: number;
   extensions: string;
   onopen: (ev: any) => mixed;
-  onmessage: (ev: MessageEvent) => mixed;
+  onmessage: (ev: MessageEvent<>) => mixed;
   onclose: (ev: CloseEvent) => mixed;
   onerror: (ev: any) => mixed;
   binaryType: 'blob' | 'arraybuffer';
@@ -855,8 +855,8 @@ declare class Worker extends EventTarget {
     workerOptions?: WorkerOptions
   ): void;
   onerror: null | ((ev: any) => mixed);
-  onmessage: null | ((ev: MessageEvent) => mixed);
-  onmessageerror: null | ((ev: MessageEvent) => mixed);
+  onmessage: null | ((ev: MessageEvent<>) => mixed);
+  onmessageerror: null | ((ev: MessageEvent<>) => mixed);
   postMessage(message: any, ports?: any): void;
   terminate(): void;
 }
@@ -888,14 +888,14 @@ declare class WorkerGlobalScope extends EventTarget {
 }
 
 declare class DedicatedWorkerGlobalScope extends WorkerGlobalScope {
-  onmessage: (ev: MessageEvent) => mixed;
-  onmessageerror: (ev: MessageEvent) => mixed;
+  onmessage: (ev: MessageEvent<>) => mixed;
+  onmessageerror: (ev: MessageEvent<>) => mixed;
   postMessage(message: any, transfer?: Iterable<any>): void;
 }
 
 declare class SharedWorkerGlobalScope extends WorkerGlobalScope {
   name: string;
-  onconnect: (ev: MessageEvent) => mixed;
+  onconnect: (ev: MessageEvent<>) => mixed;
 }
 
 declare class WorkerLocation {
@@ -2056,8 +2056,8 @@ declare class MessagePort extends EventTarget {
   start(): void;
   close(): void;
 
-  onmessage: null | ((ev: MessageEvent) => mixed);
-  onmessageerror: null | ((ev: MessageEvent) => mixed);
+  onmessage: null | ((ev: MessageEvent<>) => mixed);
+  onmessageerror: null | ((ev: MessageEvent<>) => mixed);
 }
 
 declare class MessageChannel {

flow-typed/environments/dom.js

@@ -151,7 +151,7 @@ type TransitionEventHandler = (event: TransitionEvent) => mixed;
 type TransitionEventListener =
   | {handleEvent: TransitionEventHandler, ...}
   | TransitionEventHandler;
-type MessageEventHandler = (event: MessageEvent) => mixed;
+type MessageEventHandler = (event: MessageEvent<>) => mixed;
 type MessageEventListener =
   | {handleEvent: MessageEventHandler, ...}
   | MessageEventHandler;
@@ -845,8 +845,8 @@ declare class PageTransitionEvent extends Event {
 // https://www.w3.org/TR/2008/WD-html5-20080610/comms.html
 // and
 // https://html.spec.whatwg.org/multipage/comms.html#the-messageevent-interfaces
-declare class MessageEvent extends Event {
-  data: mixed;
+declare class MessageEvent<Data = mixed> extends Event {
+  data: Data;
   origin: string;
   lastEventId: string;
   source: WindowProxy;

flow-typed/environments/html.js

@@ -109,8 +109,8 @@ declare class ErrorEvent extends Event {
 // https://html.spec.whatwg.org/multipage/web-messaging.html#broadcasting-to-other-browsing-contexts
 declare class BroadcastChannel extends EventTarget {
   name: string;
-  onmessage: ?(event: MessageEvent) => void;
-  onmessageerror: ?(event: MessageEvent) => void;
+  onmessage: ?(event: MessageEvent<>) => void;
+  onmessageerror: ?(event: MessageEvent<>) => void;
 
   constructor(name: string): void;
   postMessage(msg: mixed): void;

packages/react-devtools-core/src/backend.js

@@ -293,7 +293,7 @@ export function connectToDevTools(options: ?ConnectOptions) {
     scheduleRetry();
   }
 
-  function handleMessage(event: MessageEvent) {
+  function handleMessage(event: MessageEvent<>) {
     let data;
     try {
       if (typeof event.data === 'string') {

packages/react-devtools-extensions/src/contentScripts/hookSettingsInjector.js

@@ -1,38 +1,50 @@
 /* global chrome */
+/** @flow */
 
 // We can't use chrome.storage domain from scripts which are injected in ExecutionWorld.MAIN
 // This is the only purpose of this script - to send persisted settings to installHook.js content script
 
-async function messageListener(event: MessageEvent) {
+import type {UnknownMessageEvent} from './messages';
+import type {DevToolsHookSettings} from 'react-devtools-shared/src/backend/types';
+import {postMessage} from './messages';
+
+async function messageListener(event: UnknownMessageEvent) {
   if (event.source !== window) {
     return;
   }
 
   if (event.data.source === 'react-devtools-hook-installer') {
     if (event.data.payload.handshake) {
-      const settings = await chrome.storage.local.get();
+      const settings: Partial<DevToolsHookSettings> =
+        await chrome.storage.local.get();
       // If storage was empty (first installation), define default settings
-      if (typeof settings.appendComponentStack !== 'boolean') {
-        settings.appendComponentStack = true;
-      }
-      if (typeof settings.breakOnConsoleErrors !== 'boolean') {
-        settings.breakOnConsoleErrors = false;
-      }
-      if (typeof settings.showInlineWarningsAndErrors !== 'boolean') {
-        settings.showInlineWarningsAndErrors = true;
-      }
-      if (typeof settings.hideConsoleLogsInStrictMode !== 'boolean') {
-        settings.hideConsoleLogsInStrictMode = false;
-      }
-      if (
-        typeof settings.disableSecondConsoleLogDimmingInStrictMode !== 'boolean'
-      ) {
-        settings.disableSecondConsoleLogDimmingInStrictMode = false;
-      }
+      const hookSettings: DevToolsHookSettings = {
+        appendComponentStack:
+          typeof settings.appendComponentStack === 'boolean'
+            ? settings.appendComponentStack
+            : true,
+        breakOnConsoleErrors:
+          typeof settings.breakOnConsoleErrors === 'boolean'
+            ? settings.breakOnConsoleErrors
+            : false,
+        showInlineWarningsAndErrors:
+          typeof settings.showInlineWarningsAndErrors === 'boolean'
+            ? settings.showInlineWarningsAndErrors
+            : true,
+        hideConsoleLogsInStrictMode:
+          typeof settings.hideConsoleLogsInStrictMode === 'boolean'
+            ? settings.hideConsoleLogsInStrictMode
+            : false,
+        disableSecondConsoleLogDimmingInStrictMode:
+          typeof settings.disableSecondConsoleLogDimmingInStrictMode ===
+          'boolean'
+            ? settings.disableSecondConsoleLogDimmingInStrictMode
+            : false,
+      };
 
-      window.postMessage({
+      postMessage({
         source: 'react-devtools-hook-settings-injector',
-        payload: {settings},
+        payload: {settings: hookSettings},
       });
 
       window.removeEventListener('message', messageListener);
@@ -41,7 +53,7 @@ async function messageListener(event: MessageEvent) {
 }
 
 window.addEventListener('message', messageListener);
-window.postMessage({
+postMessage({
   source: 'react-devtools-hook-settings-injector',
   payload: {handshake: true},
 });

packages/react-devtools-extensions/src/contentScripts/installHook.js

@@ -1,39 +1,46 @@
+/** @flow */
+
+import type {UnknownMessageEvent} from './messages';
+import type {DevToolsHookSettings} from 'react-devtools-shared/src/backend/types';
+
 import {installHook} from 'react-devtools-shared/src/hook';
 import {
   getIfReloadedAndProfiling,
   getProfilingSettings,
 } from 'react-devtools-shared/src/utils';
+import {postMessage} from './messages';
 
-let resolveHookSettingsInjection;
+let resolveHookSettingsInjection: (settings: DevToolsHookSettings) => void;
 
-function messageListener(event: MessageEvent) {
+function messageListener(event: UnknownMessageEvent) {
   if (event.source !== window) {
     return;
   }
 
   if (event.data.source === 'react-devtools-hook-settings-injector') {
+    const payload = event.data.payload;
     // In case handshake message was sent prior to hookSettingsInjector execution
     // We can't guarantee order
-    if (event.data.payload.handshake) {
-      window.postMessage({
+    if (payload.handshake) {
+      postMessage({
         source: 'react-devtools-hook-installer',
         payload: {handshake: true},
       });
-    } else if (event.data.payload.settings) {
+    } else if (payload.settings) {
       window.removeEventListener('message', messageListener);
-      resolveHookSettingsInjection(event.data.payload.settings);
+      resolveHookSettingsInjection(payload.settings);
     }
   }
 }
 
 // Avoid double execution
 if (!window.hasOwnProperty('__REACT_DEVTOOLS_GLOBAL_HOOK__')) {
-  const hookSettingsPromise = new Promise(resolve => {
+  const hookSettingsPromise = new Promise<DevToolsHookSettings>(resolve => {
     resolveHookSettingsInjection = resolve;
   });
 
   window.addEventListener('message', messageListener);
-  window.postMessage({
+  postMessage({
     source: 'react-devtools-hook-installer',
     payload: {handshake: true},
   });

packages/react-devtools-extensions/src/contentScripts/messages.js

@@ -0,0 +1,42 @@
+/** @flow */
+
+import type {DevToolsHookSettings} from 'react-devtools-shared/src/backend/types';
+
+export function postMessage(event: UnknownMessageEventData): void {
+  window.postMessage(event);
+}
+
+export interface UnknownMessageEvent
+  extends MessageEvent<UnknownMessageEventData> {}
+
+export type UnknownMessageEventData =
+  | HookSettingsInjectorEventData
+  | HookInstallerEventData;
+
+export type HookInstallerEventData = {
+  source: 'react-devtools-hook-installer',
+  payload: HookInstallerEventPayload,
+};
+
+export type HookInstallerEventPayload = HookInstallerEventPayloadHandshake;
+
+export type HookInstallerEventPayloadHandshake = {
+  handshake: true,
+};
+
+export type HookSettingsInjectorEventData = {
+  source: 'react-devtools-hook-settings-injector',
+  payload: HookSettingsInjectorEventPayload,
+};
+
+export type HookSettingsInjectorEventPayload =
+  | HookSettingsInjectorEventPayloadHandshake
+  | HookSettingsInjectorEventPayloadSettings;
+
+export type HookSettingsInjectorEventPayloadHandshake = {
+  handshake: true,
+};
+
+export type HookSettingsInjectorEventPayloadSettings = {
+  settings: DevToolsHookSettings,
+};

packages/react-reconciler/src/ReactFiberTreeReflection.js

@@ -33,25 +33,24 @@ import {NoFlags, Placement, Hydrating} from './ReactFiberFlags';
 export function getNearestMountedFiber(fiber: Fiber): null | Fiber {
   let node = fiber;
   let nearestMounted: null | Fiber = fiber;
-  if (!fiber.alternate) {
-    // If there is no alternate, this might be a new tree that isn't inserted
-    // yet. If it is, then it will have a pending insertion effect on it.
-    let nextNode: Fiber = node;
-    do {
-      node = nextNode;
-      if ((node.flags & (Placement | Hydrating)) !== NoFlags) {
-        // This is an insertion or in-progress hydration. The nearest possible
-        // mounted fiber is the parent but we need to continue to figure out
-        // if that one is still mounted.
-        nearestMounted = node.return;
-      }
-      // $FlowFixMe[incompatible-type] we bail out when we get a null
-      nextNode = node.return;
-    } while (nextNode);
-  } else {
-    while (node.return) {
-      node = node.return;
+  // If there is no alternate, this might be a new tree that isn't inserted
+  // yet. If it is, then it will have a pending insertion effect on it.
+  let nextNode: Fiber = node;
+  while (nextNode && !nextNode.alternate) {
+    node = nextNode;
+    if ((node.flags & (Placement | Hydrating)) !== NoFlags) {
+      // This is an insertion or in-progress hydration. The nearest possible
+      // mounted fiber is the parent but we need to continue to figure out
+      // if that one is still mounted.
+      nearestMounted = node.return;
     }
+    // $FlowFixMe[incompatible-type] we bail out when we get a null
+    nextNode = node.return;
+  }
+  // After we've reached an alternate, go the rest of the way to see if the
+  // tree is still mounted. If it's not, its return pointer will be disconnected.
+  while (node.return) {
+    node = node.return;
   }
   if (node.tag === HostRoot) {
     // TODO: Check if this was a nested HostRoot when used with