eslint: Fix how we break lines at operators.

This is something Prettier gets wrong, but thanks to prettier-eslint
we can now fix.

prettier-eslint internally consists of two steps: prettier, and
`eslint --fix`.  When the latter fixes a case of this, it can make the
later line a few characters longer.  That causes me to notice that
we're trying to have ESLint enforce a max line length, because we have
one spot where it causes a lint error.  So also turn that off, in
favor of letting prettier do prettier's job.

This change is entirely mechanical outside of the ESLint config;
just reran `yarn run prettier`, which runs prettier-eslint.

.eslintrc.yaml

@@ -28,6 +28,7 @@ rules:
   new-cap: [error, {capIsNew: false}]
   comma-dangle: [error, always-multiline]
   quote-props: off
+  max-len: off  # This is prettier's job.
   indent: off
   arrow-parens: off
   no-confusing-arrow: off
@@ -40,6 +41,21 @@ rules:
   nonblock-statement-body-position: [error, below]
   curly: [error, all]
 
+  # When breaking a line at a binary operator, the operator goes
+  # at the start of a line, not the end.  This makes it much more
+  # conspicuous whether we're using e.g. `&&` or `||`.
+  operator-linebreak:
+  - error
+  - before
+  - overrides:
+      # Assignment operators are a very different beast, which it would make
+      # no sense to format this way.
+      "=": after
+      "+=": after
+      "-=": after
+      # ... There are 10 other assignment operators in JavaScript;
+      # if they come up, add them.
+
   # Tricky code.  We repeal several bans from the Airbnb style.
   no-bitwise: off
   no-continue: off

src/events/eventMiddleware.js

@@ -18,9 +18,9 @@ export default (state: GlobalState, event: Object) => {
       const activeAccount = getActiveAccount(state);
       const { narrow } = getChatScreenParams(state);
       const isUserInSameNarrow =
-        activeAccount &&
-        (narrow !== undefined && // chat screen is not at top
-          (!isHomeNarrow(narrow) && isMessageInNarrow(event.message, narrow, activeAccount.email)));
+        activeAccount
+        && (narrow !== undefined // chat screen is not at top
+          && (!isHomeNarrow(narrow) && isMessageInNarrow(event.message, narrow, activeAccount.email)));
       const isSenderSelf = getOwnEmail(state) === event.message.sender_email;
       if (!isUserInSameNarrow && !isSenderSelf) {
         playMessageSound();

src/message/fetchActions.js

@@ -162,8 +162,8 @@ export const fetchEssentialInitialData = () => async (dispatch: Dispatch, getSta
   const narrow = getTopMostNarrow(getState());
   const [initData, messages] = await Promise.all([
     await tryUntilSuccessful(() => registerForEvents(auth)),
-    narrow &&
-      (await tryUntilSuccessful(() => getMessages(auth, narrow, 0, halfCount, halfCount, true))),
+    narrow
+      && (await tryUntilSuccessful(() => getMessages(auth, narrow, 0, halfCount, halfCount, true))),
   ]);
 
   timing.end('Essential server data');

src/message/messageUpdates.js

@@ -28,27 +28,27 @@ export const getMessageTransitionProps = (prevProps: Props, nextProps: Props): T
   const allNewMessages =
     sameNarrow && prevProps.messages.length === 0 && nextProps.messages.length > 0;
   const oldMessagesAdded =
-    sameNarrow &&
-    prevProps.messages.length > 0 &&
-    nextProps.messages.length > 0 &&
-    prevProps.messages[0].id > nextProps.messages[0].id;
+    sameNarrow
+    && prevProps.messages.length > 0
+    && nextProps.messages.length > 0
+    && prevProps.messages[0].id > nextProps.messages[0].id;
   const newMessagesAdded =
-    sameNarrow &&
-    prevProps.messages.length > 0 &&
-    nextProps.messages.length > 0 &&
-    prevProps.messages[prevProps.messages.length - 1].id <
-      nextProps.messages[nextProps.messages.length - 1].id;
+    sameNarrow
+    && prevProps.messages.length > 0
+    && nextProps.messages.length > 0
+    && prevProps.messages[prevProps.messages.length - 1].id
+      < nextProps.messages[nextProps.messages.length - 1].id;
   const onlyOneNewMessage =
-    sameNarrow &&
-    prevProps.messages.length > 0 &&
-    nextProps.messages.length > 1 &&
-    prevProps.messages[prevProps.messages.length - 1].id ===
-      nextProps.messages[nextProps.messages.length - 2].id;
+    sameNarrow
+    && prevProps.messages.length > 0
+    && nextProps.messages.length > 1
+    && prevProps.messages[prevProps.messages.length - 1].id
+      === nextProps.messages[nextProps.messages.length - 2].id;
   const messagesReplaced =
-    sameNarrow &&
-    prevProps.messages.length > 0 &&
-    nextProps.messages.length > 0 &&
-    prevProps.messages[prevProps.messages.length - 1].id < nextProps.messages[0].id;
+    sameNarrow
+    && prevProps.messages.length > 0
+    && nextProps.messages.length > 0
+    && prevProps.messages[prevProps.messages.length - 1].id < nextProps.messages[0].id;
 
   return {
     sameNarrow,
@@ -66,15 +66,15 @@ export const getMessageUpdateStrategy = (transitionProps: TransitionProps): Upda
   if (transitionProps.noMessages) {
     return 'replace';
   } else if (
-    !transitionProps.sameNarrow ||
-    transitionProps.allNewMessages ||
-    transitionProps.messagesReplaced
+    !transitionProps.sameNarrow
+    || transitionProps.allNewMessages
+    || transitionProps.messagesReplaced
   ) {
     return 'scroll-to-anchor';
   } else if (
-    transitionProps.noNewMessages ||
-    transitionProps.oldMessagesAdded ||
-    (transitionProps.newMessagesAdded && !transitionProps.onlyOneNewMessage)
+    transitionProps.noNewMessages
+    || transitionProps.oldMessagesAdded
+    || (transitionProps.newMessagesAdded && !transitionProps.onlyOneNewMessage)
   ) {
     return 'preserve-position';
   } else if (transitionProps.onlyOneNewMessage) {

src/message/renderMessages.js

@@ -11,8 +11,8 @@ export default (messages: Message[], narrow: Narrow): RenderedSectionDescriptor[
   return messages.reduce(
     (sections, item) => {
       const diffDays =
-        prevItem &&
-        !isSameDay(new Date(prevItem.timestamp * 1000), new Date(item.timestamp * 1000));
+        prevItem
+        && !isSameDay(new Date(prevItem.timestamp * 1000), new Date(item.timestamp * 1000));
       if (!prevItem || diffDays) {
         sections[sections.length - 1].data.push({
           key: `time${item.timestamp}`,
@@ -30,10 +30,10 @@ export default (messages: Message[], narrow: Narrow): RenderedSectionDescriptor[
         });
       }
       const shouldGroupWithPrev =
-        !diffRecipient &&
-        !diffDays &&
-        prevItem &&
-        prevItem.sender_full_name === item.sender_full_name;
+        !diffRecipient
+        && !diffDays
+        && prevItem
+        && prevItem.sender_full_name === item.sender_full_name;
 
       sections[sections.length - 1].data.push({
         key: item.id,

src/nav/ModalSearchNavBar.js

@@ -81,8 +81,8 @@ class ModalSearchNavBar extends PureComponent<Props, State> {
           <Label style={textStyle} text={title} />
         )}
         {!showSearchInput && <NavButton name="search" onPress={this.enableSearchActiveState} />}
-        {showSearchInput &&
-          clearSearchInput && (
+        {showSearchInput
+          && clearSearchInput && (
             <NavButton
               name="md-add"
               style={localStyles.buttonCancel}

src/nav/navSelectors.js

@@ -28,8 +28,8 @@ export const getSameRoutesAndParamsCount = createSelector(getNav, nav => {
   let i = nav.routes.length - 1;
   while (i >= 0) {
     if (
-      nav.routes[i].routeName !== nav.routes[nav.routes.length - 1].routeName ||
-      !isEqual(nav.routes[i].params, nav.routes[nav.routes.length - 1].params)
+      nav.routes[i].routeName !== nav.routes[nav.routes.length - 1].routeName
+      || !isEqual(nav.routes[i].params, nav.routes[nav.routes.length - 1].params)
     ) {
       break;
     }
@@ -58,9 +58,9 @@ export const getPreviousDifferentRouteAndParams = createSelector(getNav, nav =>
 
   let i = nav.routes.length - 2;
   while (
-    i >= 0 &&
-    nav.routes[i].routeName === nav.routes[nav.routes.length - 1].routeName &&
-    isEqual(nav.routes[i].params, nav.routes[nav.routes.length - 1].params)
+    i >= 0
+    && nav.routes[i].routeName === nav.routes[nav.routes.length - 1].routeName
+    && isEqual(nav.routes[i].params, nav.routes[nav.routes.length - 1].params)
   ) {
     i--;
   }

src/start/AuthScreen.js

@@ -59,12 +59,12 @@ class AuthScreen extends PureComponent<Props> {
 
     // callback format expected: zulip://login?realm={}&email={}&otp_encrypted_api_key={}
     if (
-      url.host === 'login' &&
-      url.query.realm === realm &&
-      otp &&
-      url.query.email &&
-      url.query.otp_encrypted_api_key &&
-      url.query.otp_encrypted_api_key.length === otp.length
+      url.host === 'login'
+      && url.query.realm === realm
+      && otp
+      && url.query.email
+      && url.query.otp_encrypted_api_key
+      && url.query.otp_encrypted_api_key.length === otp.length
     ) {
       const apiKey = extractApiKey(url.query.otp_encrypted_api_key, otp);
       actions.loginSuccess(realm, url.query.email, apiKey);

src/start/PasswordAuthScreen.js

@@ -83,9 +83,9 @@ class PasswordAuthView extends PureComponent<Props, State> {
     const { requireEmailFormat } = this.props.navigation.state.params;
     const { email, password, progress, error } = this.state;
     const isButtonDisabled =
-      password.length === 0 ||
-      email.length === 0 ||
-      (requireEmailFormat && !isValidEmailFormat(email));
+      password.length === 0
+      || email.length === 0
+      || (requireEmailFormat && !isValidEmailFormat(email));
 
     return (
       <Screen title="Log in" centerContent padding keyboardShouldPersistTaps="always">

src/start/RealmScreen.js

@@ -103,6 +103,6 @@ class RealmScreen extends PureComponent<Props, State> {
 
 export default connectWithActions((state, props) => ({
   initialRealm:
-    (props.navigation && props.navigation.state.params && props.navigation.state.params.realm) ||
-    '',
+    (props.navigation && props.navigation.state.params && props.navigation.state.params.realm)
+    || '',
 }))(RealmScreen);

src/start/authentications.js

@@ -44,6 +44,6 @@ const authentications = [
 export const activeAuthentications = (authenticationMethods: AuthenticationMethods) =>
   authentications.filter(
     auth =>
-      authenticationMethods[auth.method] &&
-      (auth.method !== 'ldap' || !authenticationMethods.password),
+      authenticationMethods[auth.method]
+      && (auth.method !== 'ldap' || !authenticationMethods.password),
   );

src/streams/StreamItem.js

@@ -83,11 +83,11 @@ export default class StreamItem extends PureComponent<Props> {
     ];
     const iconColor = isSelected
       ? 'white'
-      : color ||
-        foregroundColorFromBackground(
-          backgroundColor || // $FlowFixMe
-            (StyleSheet.flatten(styles.backgroundColor) || {}).backgroundColor ||
-            null,
+      : color
+        || foregroundColorFromBackground(
+          backgroundColor // $FlowFixMe
+            || (StyleSheet.flatten(styles.backgroundColor) || {}).backgroundColor
+            || null,
         );
     const textColorStyle = isSelected
       ? { color: 'white' }

src/users/userHelpers.js

@@ -48,18 +48,18 @@ const statusOrder = (presence: Presence): number => {
 export const sortUserList = (users: any[], presences: PresenceState): User[] =>
   [...users].sort(
     (x1, x2) =>
-      statusOrder(presences[x1.email]) - statusOrder(presences[x2.email]) ||
-      x1.full_name.toLowerCase().localeCompare(x2.full_name.toLowerCase()),
+      statusOrder(presences[x1.email]) - statusOrder(presences[x2.email])
+      || x1.full_name.toLowerCase().localeCompare(x2.full_name.toLowerCase()),
   );
 
 export const filterUserList = (users: User[], filter: string = '', ownEmail: ?string): User[] =>
   users.length > 0
     ? users.filter(
         user =>
-          user.email !== ownEmail &&
-          (filter === '' ||
-            user.full_name.toLowerCase().includes(filter.toLowerCase()) ||
-            user.email.toLowerCase().includes(filter.toLowerCase())),
+          user.email !== ownEmail
+          && (filter === ''
+            || user.full_name.toLowerCase().includes(filter.toLowerCase())
+            || user.email.toLowerCase().includes(filter.toLowerCase())),
       )
     : users;
 
@@ -79,8 +79,8 @@ export const filterUserByInitials = (
 ): User[] =>
   users.filter(
     user =>
-      user.email !== ownEmail &&
-      user.full_name
+      user.email !== ownEmail
+      && user.full_name
         .replace(/(\s|[a-z])/g, '')
         .toLowerCase()
         .startsWith(filter.toLowerCase()),

src/utils/message.js

@@ -37,13 +37,13 @@ export const isSameRecipient = (message1: Message, message2: Message): boolean =
   switch (message1.type) {
     case 'private':
       return (
-        normalizeRecipients(message1.display_recipient).toLowerCase() ===
-        normalizeRecipients(message2.display_recipient).toLowerCase()
+        normalizeRecipients(message1.display_recipient).toLowerCase()
+        === normalizeRecipients(message2.display_recipient).toLowerCase()
       );
     case 'stream':
       return (
-        message1.display_recipient.toLowerCase() === message2.display_recipient.toLowerCase() &&
-        message1.subject.toLowerCase() === message2.subject.toLowerCase()
+        message1.display_recipient.toLowerCase() === message2.display_recipient.toLowerCase()
+        && message1.subject.toLowerCase() === message2.subject.toLowerCase()
       );
     case 'outbox': {
       return message2.isOutbox;

src/utils/misc.js

@@ -28,10 +28,10 @@ export const removeEmptyValues = (obj: Object): Object => {
 };
 
 export const isStateGoingBack = (cur: GlobalState, prev: GlobalState): boolean =>
-  cur.nav.routes.length < prev.nav.routes.length ||
-  cur.nav.isTransitioning ||
-  prev.nav.isTransitioning ||
-  isEqual(cur, prev);
+  cur.nav.routes.length < prev.nav.routes.length
+  || cur.nav.isTransitioning
+  || prev.nav.isTransitioning
+  || isEqual(cur, prev);
 
 export const groupItemsById = (items: ObjectWithId[]): ObjectsMappedById =>
   items.reduce((itemsById, item) => {

src/utils/narrow.js

@@ -20,10 +20,10 @@ export const privateNarrow = (email: string): Narrow => [
 ];
 
 export const isPrivateNarrow = (narrow: Narrow): boolean =>
-  Array.isArray(narrow) &&
-  narrow.length === 1 &&
-  narrow[0].operator === 'pm-with' &&
-  narrow[0].operand.indexOf(',') === -1;
+  Array.isArray(narrow)
+  && narrow.length === 1
+  && narrow[0].operator === 'pm-with'
+  && narrow[0].operand.indexOf(',') === -1;
 
 export const groupNarrow = (emails: string[]): Narrow => [
   {
@@ -33,10 +33,10 @@ export const groupNarrow = (emails: string[]): Narrow => [
 ];
 
 export const isGroupNarrow = (narrow: Narrow): boolean =>
-  Array.isArray(narrow) &&
-  narrow.length === 1 &&
-  narrow[0].operator === 'pm-with' &&
-  narrow[0].operand.indexOf(',') >= 0;
+  Array.isArray(narrow)
+  && narrow.length === 1
+  && narrow[0].operator === 'pm-with'
+  && narrow[0].operand.indexOf(',') >= 0;
 
 export const isPrivateOrGroupNarrow = (narrow: Narrow): boolean =>
   Array.isArray(narrow) && narrow.length === 1 && narrow[0].operator === 'pm-with';
@@ -56,10 +56,10 @@ export const allPrivateNarrow = specialNarrow('private');
 export const allPrivateNarrowStr = JSON.stringify(allPrivateNarrow);
 
 export const isAllPrivateNarrow = (narrow: Narrow): boolean =>
-  Array.isArray(narrow) &&
-  narrow.length === 1 &&
-  narrow[0].operator === 'is' &&
-  narrow[0].operand === 'private';
+  Array.isArray(narrow)
+  && narrow.length === 1
+  && narrow[0].operator === 'is'
+  && narrow[0].operand === 'private';
 
 export const streamNarrow = (stream: string): Narrow => [
   {
@@ -108,9 +108,9 @@ export const isMessageInNarrow = (message: Message, narrow: Narrow, ownEmail: st
   }
 
   if (
-    isTopicNarrow(narrow) &&
-    message.display_recipient === narrow[0].operand &&
-    message.subject === narrow[1].operand
+    isTopicNarrow(narrow)
+    && message.display_recipient === narrow[0].operand
+    && message.subject === narrow[1].operand
   ) {
     return true;
   }
@@ -130,10 +130,10 @@ export const isMessageInNarrow = (message: Message, narrow: Narrow, ownEmail: st
 };
 
 export const canSendToNarrow = (narrow: Narrow): boolean =>
-  isPrivateNarrow(narrow) ||
-  isGroupNarrow(narrow) ||
-  isStreamNarrow(narrow) ||
-  isTopicNarrow(narrow);
+  isPrivateNarrow(narrow)
+  || isGroupNarrow(narrow)
+  || isStreamNarrow(narrow)
+  || isTopicNarrow(narrow);
 
 export const getNarrowFromMessage = (message: Message, email: string) => {
   if (Array.isArray(message.display_recipient)) {