Optimize makeGetStatus (#11211)

* Optimize makeGetStatus

Because `ImmutableList.filter` always returns a new object and `createSelector`
memoizes based on object identity, the selector returned by `makeGetStatus`
would *always* execute.

To avoid that, we wrap `getFilters` into a new memoizer that memoizes based on
deep equality, thus returning the same object as long as the filters haven't
changed, allowing the memoization of `makeGetStatus` to work.

Furthermore, we memoize the compiled regexs instead of recomputing them each
time the selector is called.

* Fix memoized result being cleared too often

* Make notifications use memoized getFiltersRegex

app/javascript/mastodon/actions/notifications.js

@@ -11,7 +11,7 @@ import { saveSettings } from './settings';
 import { defineMessages } from 'react-intl';
 import { List as ImmutableList } from 'immutable';
 import { unescapeHTML } from '../utils/html';
-import { getFilters, regexFromFilters } from '../selectors';
+import { getFiltersRegex } from '../selectors';
 
 export const NOTIFICATIONS_UPDATE      = 'NOTIFICATIONS_UPDATE';
 export const NOTIFICATIONS_UPDATE_NOOP = 'NOTIFICATIONS_UPDATE_NOOP';
@@ -43,13 +43,13 @@ export function updateNotifications(notification, intlMessages, intlLocale) {
     const showInColumn = getState().getIn(['settings', 'notifications', 'shows', notification.type], true);
     const showAlert    = getState().getIn(['settings', 'notifications', 'alerts', notification.type], true);
     const playSound    = getState().getIn(['settings', 'notifications', 'sounds', notification.type], true);
-    const filters      = getFilters(getState(), { contextType: 'notifications' });
+    const filters      = getFiltersRegex(getState(), { contextType: 'notifications' });
 
     let filtered = false;
 
     if (notification.type === 'mention') {
-      const dropRegex   = regexFromFilters(filters.filter(filter => filter.get('irreversible')));
-      const regex       = regexFromFilters(filters);
+      const dropRegex   = filters[0];
+      const regex       = filters[1];
       const searchIndex = notification.status.spoiler_text + '\n' + unescapeHTML(notification.status.content);
 
       if (dropRegex && dropRegex.test(searchIndex)) {

app/javascript/mastodon/selectors/index.js

@@ -1,5 +1,5 @@
 import { createSelector } from 'reselect';
-import { List as ImmutableList } from 'immutable';
+import { List as ImmutableList, is } from 'immutable';
 import { me } from '../initial_state';
 
 const getAccountBase         = (state, id) => state.getIn(['accounts', id], null);
@@ -36,12 +36,10 @@ const toServerSideType = columnType => {
   }
 };
 
-export const getFilters = (state, { contextType }) => state.get('filters', ImmutableList()).filter(filter => contextType && filter.get('context').includes(toServerSideType(contextType)) && (filter.get('expires_at') === null || Date.parse(filter.get('expires_at')) > (new Date())));
-
 const escapeRegExp = string =>
   string.replace(/[.*+?^${}()|[\]\\]/g, '\\$&'); // $& means the whole matched string
 
-export const regexFromFilters = filters => {
+const regexFromFilters = filters => {
   if (filters.size === 0) {
     return null;
   }
@@ -63,6 +61,27 @@ export const regexFromFilters = filters => {
   }).join('|'), 'i');
 };
 
+// Memoize the filter regexps for each valid server contextType
+const makeGetFiltersRegex = () => {
+  let memo = {};
+
+  return (state, { contextType }) => {
+    if (!contextType) return ImmutableList();
+
+    const serverSideType = toServerSideType(contextType);
+    const filters = state.get('filters', ImmutableList()).filter(filter => filter.get('context').includes(serverSideType) && (filter.get('expires_at') === null || Date.parse(filter.get('expires_at')) > (new Date())));
+
+    if (!memo[serverSideType] || !is(memo[serverSideType].filters, filters)) {
+      const dropRegex = regexFromFilters(filters.filter(filter => filter.get('irreversible')));
+      const regex = regexFromFilters(filters);
+      memo[serverSideType] = { filters: filters, results: [dropRegex, regex] };
+    }
+    return memo[serverSideType].results;
+  };
+};
+
+export const getFiltersRegex = makeGetFiltersRegex();
+
 export const makeGetStatus = () => {
   return createSelector(
     [
@@ -70,10 +89,10 @@ export const makeGetStatus = () => {
       (state, { id }) => state.getIn(['statuses', state.getIn(['statuses', id, 'reblog'])]),
       (state, { id }) => state.getIn(['accounts', state.getIn(['statuses', id, 'account'])]),
       (state, { id }) => state.getIn(['accounts', state.getIn(['statuses', state.getIn(['statuses', id, 'reblog']), 'account'])]),
-      getFilters,
+      getFiltersRegex,
     ],
 
-    (statusBase, statusReblog, accountBase, accountReblog, filters) => {
+    (statusBase, statusReblog, accountBase, accountReblog, filtersRegex) => {
       if (!statusBase) {
         return null;
       }
@@ -84,12 +103,12 @@ export const makeGetStatus = () => {
         statusReblog = null;
       }
 
-      const dropRegex = (accountReblog || accountBase).get('id') !== me && regexFromFilters(filters.filter(filter => filter.get('irreversible')));
+      const dropRegex = (accountReblog || accountBase).get('id') !== me && filtersRegex[0];
       if (dropRegex && dropRegex.test(statusBase.get('reblog') ? statusReblog.get('search_index') : statusBase.get('search_index'))) {
         return null;
       }
 
-      const regex     = (accountReblog || accountBase).get('id') !== me && regexFromFilters(filters);
+      const regex     = (accountReblog || accountBase).get('id') !== me && filtersRegex[1];
       const filtered  = regex && regex.test(statusBase.get('reblog') ? statusReblog.get('search_index') : statusBase.get('search_index'));
 
       return statusBase.withMutations(map => {