types: Mark most arrays as read-only

Done with:

  $ perl -i -0pe '
          s<( \w+ ) \[\]> (\$ReadOnlyArray<$1>)gsmx;
          s/\bArray\b</\$ReadOnlyArray</g
        ' src/**/*.js
  $ tools/fmt

followed by reviewing the changes, and reverting those that weren't
appropriate (which were perhaps 1/3 of the total) with commands like
`git restore -p src/foo/bar.js`.

src/__tests__/lib/exampleData.js

@@ -360,7 +360,7 @@ const randMessageId: () => number = makeUniqueRandInt('message ID', 10000000);
 export const pmMessage = (args?: {|
   ...$Rest<PmMessage, { ... }>,
   sender?: User,
-  recipients?: User[],
+  recipients?: $ReadOnlyArray<User>,
   sender_id?: number, // accept a plain number, for convenience in tests
 |}): PmMessage => {
   // The `Object.freeze` is to work around a Flow issue:
@@ -395,7 +395,7 @@ export const pmMessage = (args?: {|
 
 export const pmMessageFromTo = (
   from: User,
-  to: User[],
+  to: $ReadOnlyArray<User>,
   extra?: $Rest<PmMessage, { ... }>,
 ): PmMessage => pmMessage({ sender: from, recipients: [from, ...to], ...extra });
 
@@ -444,7 +444,7 @@ export const streamMessage = (args?: {|
 };
 
 /** Construct a MessagesState from a list of messages. */
-export const makeMessagesState = (messages: Message[]): MessagesState =>
+export const makeMessagesState = (messages: $ReadOnlyArray<Message>): MessagesState =>
   Immutable.Map(messages.map(m => [m.id, m]));
 
 /* ========================================================================

src/animation/AnimatedRotateComponent.js

@@ -28,7 +28,7 @@ export default class AnimatedRotateComponent extends PureComponent<Props> {
     const { children, style } = this.props;
     const rotation = this.rotation.interpolate({
       inputRange: [0, 360],
-      outputRange: (['0deg', '360deg']: string[]),
+      outputRange: (['0deg', '360deg']: $ReadOnlyArray<string>),
     });
     const animatedStyle = { transform: [{ rotate: rotation }] };
 

src/api/devListUsers.js

@@ -5,8 +5,8 @@ import { apiGet } from './apiFetch';
 
 type ApiResponseDevListUsers = {|
   ...$Exact<ApiResponseSuccess>,
-  direct_admins: DevUser[],
-  direct_users: DevUser[],
+  direct_admins: $ReadOnlyArray<DevUser>,
+  direct_users: $ReadOnlyArray<DevUser>,
 |};
 
 export default (auth: Auth): Promise<ApiResponseDevListUsers> => apiGet(auth, 'dev_list_users');

src/api/getTopics.js

@@ -5,7 +5,7 @@ import { apiGet } from './apiFetch';
 
 type ApiResponseTopics = {|
   ...$Exact<ApiResponseSuccess>,
-  topics: Topic[],
+  topics: $ReadOnlyArray<Topic>,
 |};
 
 /** See https://zulip.com/api/get-stream-topics */

src/api/messages/__tests__/migrateMessages-test.js

@@ -26,9 +26,9 @@ describe('migrateMessages', () => {
     avatar_url: null,
   };
 
-  const input: ServerMessage[] = [serverMessage];
+  const input: $ReadOnlyArray<ServerMessage> = [serverMessage];
 
-  const expectedOutput: Message[] = [
+  const expectedOutput: $ReadOnlyArray<Message> = [
     {
       ...serverMessage,
       reactions: [
@@ -43,7 +43,7 @@ describe('migrateMessages', () => {
     },
   ];
 
-  const actualOutput: Message[] = migrateMessages(input, identityOfAuth(eg.selfAuth));
+  const actualOutput: $ReadOnlyArray<Message> = migrateMessages(input, identityOfAuth(eg.selfAuth));
 
   test('In reactions, replace user object with `user_id`', () => {
     expect(actualOutput.map(m => m.reactions)).toEqual(expectedOutput.map(m => m.reactions));

src/api/messages/getMessageHistory.js

@@ -5,7 +5,7 @@ import { apiGet } from '../apiFetch';
 
 type ApiResponseMessageHistory = {|
   ...$Exact<ApiResponseSuccess>,
-  message_history: MessageSnapshot[],
+  message_history: $ReadOnlyArray<MessageSnapshot>,
 |};
 
 /** See https://zulip.com/api/get-message-history */

src/api/messages/getMessages.js

@@ -13,7 +13,7 @@ type ApiResponseMessages = {|
   found_anchor: boolean,
   found_newest: boolean,
   found_oldest: boolean,
-  messages: Message[],
+  messages: $ReadOnlyArray<Message>,
 |};
 
 /**
@@ -49,7 +49,7 @@ export type ServerMessage = ServerMessageOf<PmMessage> | ServerMessageOf<StreamM
 // `ApiResponseMessages` before returning it to application code.
 type ServerApiResponseMessages = {|
   ...ApiResponseMessages,
-  messages: ServerMessage[],
+  messages: $ReadOnlyArray<ServerMessage>,
 |};
 
 /** Exported for tests only. */

src/api/messages/messagesFlags.js

@@ -4,7 +4,7 @@ import { apiPost } from '../apiFetch';
 
 export type ApiResponseMessagesFlags = {|
   ...$Exact<ApiResponseSuccess>,
-  messages: number[],
+  messages: $ReadOnlyArray<number>,
 |};
 
 export default (

src/api/messages/toggleMessageStarred.js

@@ -5,7 +5,7 @@ import type { ApiResponseMessagesFlags } from './messagesFlags';
 
 export default (
   auth: Auth,
-  messageIds: number[],
+  messageIds: $ReadOnlyArray<number>,
   starMessage: boolean,
 ): Promise<ApiResponseMessagesFlags> =>
   messagesFlags(auth, messageIds, starMessage ? 'add' : 'remove', 'starred');

src/api/pollForEvents.js

@@ -5,7 +5,7 @@ import { apiGet } from './apiFetch';
 
 type ApiResponsePollEvents = {|
   ...$Exact<ApiResponseSuccess>,
-  events: GeneralEvent[],
+  events: $ReadOnlyArray<GeneralEvent>,
 |};
 
 /** See https://zulip.com/api/get-events */

src/api/queueMarkAsRead.js

@@ -36,7 +36,7 @@ const processQueue = async (auth: Auth) => {
   unackedMessageIds = unackedMessageIds.filter(id => !acked_messages.has(id));
 };
 
-export default (auth: Auth, messageIds: number[]): void => {
+export default (auth: Auth, messageIds: $ReadOnlyArray<number>): void => {
   unackedMessageIds.push(...messageIds);
   processQueue(auth);
 };

src/api/settings/getServerSettings.js

@@ -27,7 +27,7 @@ export type ApiResponseServerSettings = {|
   authentication_methods: AuthenticationMethods,
   // external_authentication_methods added for server v2.1
   // TODO(server-2.1): Mark this as required; simplify downstream.
-  external_authentication_methods?: ExternalAuthenticationMethod[],
+  external_authentication_methods?: $ReadOnlyArray<ExternalAuthenticationMethod>,
   email_auth_enabled: boolean,
   push_notifications_enabled: boolean,
   realm_description: string,

src/api/streams/createStream.js

@@ -7,7 +7,7 @@ export default (
   auth: Auth,
   name: string,
   description?: string = '',
-  principals?: string[] = [],
+  principals?: $ReadOnlyArray<string> = [],
   inviteOnly?: boolean = false,
   announce?: boolean = false,
 ): Promise<ApiResponse> =>

src/api/streams/getStreams.js

@@ -5,7 +5,7 @@ import { apiGet } from '../apiFetch';
 
 type ApiResponseStreams = {|
   ...$Exact<ApiResponseSuccess>,
-  streams: Stream[],
+  streams: $ReadOnlyArray<Stream>,
 |};
 
 /** See https://zulip.com/api/get-streams */

src/api/subscriptions/getSubscriptions.js

@@ -5,7 +5,7 @@ import { apiGet } from '../apiFetch';
 
 type ApiResponseSubscriptions = {|
   ...$Exact<ApiResponseSuccess>,
-  subscriptions: Subscription[],
+  subscriptions: $ReadOnlyArray<Subscription>,
 |};
 
 /** See https://zulip.com/api/get-subscriptions */

src/api/subscriptions/subscriptionAdd.js

@@ -9,8 +9,8 @@ type SubscriptionObj = {|
 /** See https://zulip.com/api/subscribe */
 export default (
   auth: Auth,
-  subscriptions: SubscriptionObj[],
-  principals?: string[],
+  subscriptions: $ReadOnlyArray<SubscriptionObj>,
+  principals?: $ReadOnlyArray<string>,
 ): Promise<ApiResponse> =>
   apiPost(auth, 'users/me/subscriptions', {
     subscriptions: JSON.stringify(subscriptions),

src/api/subscriptions/subscriptionRemove.js

@@ -3,7 +3,11 @@ import type { ApiResponse, Auth } from '../transportTypes';
 import { apiDelete } from '../apiFetch';
 
 /** See https://zulip.com/api/unsubscribe */
-export default (auth: Auth, subscriptions: string[], principals?: string[]): Promise<ApiResponse> =>
+export default (
+  auth: Auth,
+  subscriptions: $ReadOnlyArray<string>,
+  principals?: $ReadOnlyArray<string>,
+): Promise<ApiResponse> =>
   apiDelete(auth, 'users/me/subscriptions', {
     subscriptions: JSON.stringify(subscriptions),
     principals: JSON.stringify(principals),

src/boot/store.js

@@ -44,7 +44,7 @@ if (process.env.NODE_ENV === 'development') {
  * the lists of properties we do persist, below.
  */
 // prettier-ignore
-export const discardKeys: Array<$Keys<GlobalState>> = [
+export const discardKeys: $ReadOnlyArray<$Keys<GlobalState>> = [
   'alertWords', 'caughtUp', 'fetching',
   'presence', 'session', 'topics', 'typing', 'userStatus',
 ];
@@ -57,7 +57,7 @@ export const discardKeys: Array<$Keys<GlobalState>> = [
  * persist them.
  */
 // prettier-ignore
-export const storeKeys: Array<$Keys<GlobalState>> = [
+export const storeKeys: $ReadOnlyArray<$Keys<GlobalState>> = [
   'migrations', 'accounts', 'drafts', 'outbox', 'settings',
 ];
 
@@ -69,7 +69,7 @@ export const storeKeys: Array<$Keys<GlobalState>> = [
  * don't have to re-download it.
  */
 // prettier-ignore
-export const cacheKeys: Array<$Keys<GlobalState>> = [
+export const cacheKeys: $ReadOnlyArray<$Keys<GlobalState>> = [
   'flags', 'messages', 'mute', 'mutedUsers', 'narrows', 'pmConversations',
   'realm', 'streams', 'subscriptions', 'unread', 'userGroups', 'users',
 ];

src/chat/narrowsSelectors.js

@@ -65,7 +65,7 @@ export const getFetchedMessageIdsForNarrow = (
   narrow: Narrow,
 ): $ReadOnlyArray<number> => getAllNarrows(state).get(keyFromNarrow(narrow)) || NULL_ARRAY;
 
-const getFetchedMessagesForNarrow: Selector<Message[], Narrow> = createSelector(
+const getFetchedMessagesForNarrow: Selector<$ReadOnlyArray<Message>, Narrow> = createSelector(
   getFetchedMessageIdsForNarrow,
   state => getMessages(state),
   (messageIds, messages) =>

src/common/GroupAvatar.js

@@ -18,7 +18,7 @@ const styles = createStyleSheet({
 });
 
 type Props = $ReadOnly<{|
-  names: string[],
+  names: $ReadOnlyArray<string>,
   size: number,
   children?: Node,
   onPress?: () => void,

src/compose/ComposeBox.js

@@ -235,7 +235,7 @@ class ComposeBoxInner extends PureComponent<Props, State> {
     }
   };
 
-  insertAttachment = async (attachments: DocumentPickerResponse[]) => {
+  insertAttachment = async (attachments: $ReadOnlyArray<DocumentPickerResponse>) => {
     this.setState(({ numUploading }) => ({
       numUploading: numUploading + 1,
     }));

src/compose/ComposeMenu.js

@@ -26,7 +26,7 @@ import { androidEnsureStoragePermission } from '../lightbox/download';
 type OuterProps = $ReadOnly<{|
   expanded: boolean,
   destinationNarrow: Narrow,
-  insertAttachment: (DocumentPickerResponse[]) => Promise<void>,
+  insertAttachment: ($ReadOnlyArray<DocumentPickerResponse>) => Promise<void>,
   insertVideoCallLink: (() => void) | null,
   onExpandContract: () => void,
 |}>;
@@ -206,7 +206,7 @@ class ComposeMenuInner extends PureComponent<Props> {
     try {
       response = (await DocumentPicker.pickMultiple({
         type: [DocumentPicker.types.allFiles],
-      }): DocumentPickerResponse[]);
+      }): $ReadOnlyArray<DocumentPickerResponse>);
     } catch (e) {
       if (!DocumentPicker.isCancel(e)) {
         showErrorAlert(_('Error'), e);

src/compose/MentionWarnings.js

@@ -43,7 +43,7 @@ function MentionWarningsInner(props: Props, ref): Node {
   const auth = useSelector(getAuth);
   const allUsersById = useSelector(getAllUsersById);
 
-  const [unsubscribedMentions, setUnsubscribedMentions] = useState<UserId[]>([]);
+  const [unsubscribedMentions, setUnsubscribedMentions] = useState<$ReadOnlyArray<UserId>>([]);
 
   const _ = useContext(TranslationContext);
 

src/config.js

@@ -9,7 +9,7 @@ type Config = {|
   enableReduxSlowReducerWarnings: boolean,
   slowReducersThreshold: number,
   enableErrorConsoleLogging: boolean,
-  appOwnDomains: string[],
+  appOwnDomains: $ReadOnlyArray<string>,
 |};
 
 const config: Config = {

src/lightbox/LightboxActionSheet.js

@@ -57,7 +57,7 @@ const shareImageDirectly = ({ src, auth }: DownloadImageType) => {
   shareImage(src, auth);
 };
 
-const actionSheetButtons: ButtonType[] = [
+const actionSheetButtons: $ReadOnlyArray<ButtonType> = [
   { title: 'Download image', onPress: tryToDownloadImage },
   { title: 'Share image', onPress: shareImageDirectly },
   { title: 'Share link to image', onPress: shareLink },

src/message/NoMessages.js

@@ -37,7 +37,7 @@ type EmptyMessage = {|
   text: string,
 |};
 
-const messages: EmptyMessage[] = [
+const messages: $ReadOnlyArray<EmptyMessage> = [
   { isFunc: isHomeNarrow, text: 'No messages on server' },
   { isFunc: isSpecialNarrow, text: 'No messages' },
   { isFunc: isStreamNarrow, text: 'No messages in stream' },

src/message/fetchActions.js

@@ -67,7 +67,7 @@ const messageFetchError = (args: {| narrow: Narrow, error: Error |}): PerAccount
 };
 
 const messageFetchComplete = (args: {|
-  messages: Message[],
+  messages: $ReadOnlyArray<Message>,
   narrow: Narrow,
   anchor: number,
   numBefore: number,
@@ -111,7 +111,7 @@ export const fetchMessages = (fetchArgs: {|
   anchor: number,
   numBefore: number,
   numAfter: number,
-|}): ThunkAction<Promise<Message[]>> => async (dispatch, getState) => {
+|}): ThunkAction<Promise<$ReadOnlyArray<Message>>> => async (dispatch, getState) => {
   dispatch(messageFetchStart(fetchArgs.narrow, fetchArgs.numBefore, fetchArgs.numAfter));
   try {
     const { messages, found_newest, found_oldest } =
@@ -308,7 +308,7 @@ export const isFetchNeededAtAnchor = (
 export const fetchMessagesInNarrow = (
   narrow: Narrow,
   anchor: number = FIRST_UNREAD_ANCHOR,
-): ThunkAction<Promise<Message[] | void>> => async (dispatch, getState) => {
+): ThunkAction<Promise<$ReadOnlyArray<Message> | void>> => async (dispatch, getState) => {
   if (!isFetchNeededAtAnchor(getState(), narrow, anchor)) {
     return undefined;
   }

src/message/messageSelectors.js

@@ -33,7 +33,7 @@ function truncateForLogging<T: JSONable>(arr: $ReadOnlyArray<T>, len = 10): JSON
   };
 }
 
-export const getPrivateMessages: Selector<PmMessage[]> = createSelector(
+export const getPrivateMessages: Selector<$ReadOnlyArray<PmMessage>> = createSelector(
   getAllNarrows,
   getMessages,
   (narrows, messages) => {

src/pm-conversations/PmConversationList.js

@@ -21,7 +21,7 @@ const styles = createStyleSheet({
 });
 
 type Props = $ReadOnly<{|
-  conversations: PmConversationData[],
+  conversations: $ReadOnlyArray<PmConversationData>,
 |}>;
 
 /**

src/pm-conversations/pmConversationsModel.js

@@ -42,7 +42,7 @@ export function keyOfExactUsers(ids: UserId[]): PmConversationKey {
 }
 
 // Input may contain self or not, and needn't be sorted.
-function keyOfUsers(ids: UserId[], ownUserId: UserId): PmConversationKey {
+function keyOfUsers(ids: $ReadOnlyArray<UserId>, ownUserId: UserId): PmConversationKey {
   return keyOfExactUsers(ids.filter(id => id !== ownUserId));
 }