Lazy load components (#3879)

* feat: Lazy-load routes

* feat: Lazy-load modals

* feat: Lazy-load columns

* refactor: Simplify Bundle API

* feat: Optimize bundles

* feat: Prevent flashing the waiting state

* feat: Preload commonly used bundles

* feat: Lazy load Compose reducers

* feat: Lazy load Notifications reducer

* refactor: Move all dynamic imports into one file

* fix: Minor bugs

* fix: Manually hydrate the lazy-loaded reducers

* refactor: Move all dynamic imports to async-components

* fix: Loading modal style

* refactor: Avoid converting the raw state for each lazy hydration

* refactor: Remove unused component

* refactor: Maintain modal name

* fix: Add as=script to preload link

* chore: Fix lint error

* fix(components/bundle): Check if timestamp is set when computing elapsed

* fix: Load compose reducers for the onboarding modal

22 files changed, 680 insertions, 111 deletions

diff --git a/app/javascript/mastodon/actions/bundles.js b/app/javascript/mastodon/actions/bundles.js
new file mode 100644
index 000000000..ecc9c8f7d
--- /dev/null
+++ b/app/javascript/mastodon/actions/bundles.js
@@ -0,0 +1,25 @@
+export const BUNDLE_FETCH_REQUEST = 'BUNDLE_FETCH_REQUEST';
+export const BUNDLE_FETCH_SUCCESS = 'BUNDLE_FETCH_SUCCESS';
+export const BUNDLE_FETCH_FAIL = 'BUNDLE_FETCH_FAIL';
+
+export function fetchBundleRequest(skipLoading) {
+  return {
+    type: BUNDLE_FETCH_REQUEST,
+    skipLoading,
+  };
+}
+
+export function fetchBundleSuccess(skipLoading) {
+  return {
+    type: BUNDLE_FETCH_SUCCESS,
+    skipLoading,
+  };
+}
+
+export function fetchBundleFail(error, skipLoading) {
+  return {
+    type: BUNDLE_FETCH_FAIL,
+    error,
+    skipLoading,
+  };
+}
diff --git a/app/javascript/mastodon/actions/store.js b/app/javascript/mastodon/actions/store.js
index 601cea001..08c2810ca 100644
--- a/app/javascript/mastodon/actions/store.js
+++ b/app/javascript/mastodon/actions/store.js
@@ -1,6 +1,7 @@
 import Immutable from 'immutable';
 
 export const STORE_HYDRATE = 'STORE_HYDRATE';
+export const STORE_HYDRATE_LAZY = 'STORE_HYDRATE_LAZY';
 
 const convertState = rawState =>
   Immutable.fromJS(rawState, (k, v) =>
@@ -15,3 +16,10 @@ export function hydrateStore(rawState) {
     state,
   };
 };
+
+export function hydrateStoreLazy(name, state) {
+  return {
+    type: `${STORE_HYDRATE_LAZY}-${name}`,
+    state,
+  };
+};
diff --git a/app/javascript/mastodon/components/status.js b/app/javascript/mastodon/components/status.js
index ff574ab3d..18ce0198e 100644
--- a/app/javascript/mastodon/components/status.js
+++ b/app/javascript/mastodon/components/status.js
@@ -5,8 +5,6 @@ import Avatar from './avatar';
 import AvatarOverlay from './avatar_overlay';
 import RelativeTimestamp from './relative_timestamp';
 import DisplayName from './display_name';
-import MediaGallery from './media_gallery';
-import VideoPlayer from './video_player';
 import StatusContent from './status_content';
 import StatusActionBar from './status_action_bar';
 import { FormattedMessage } from 'react-intl';
@@ -14,6 +12,11 @@ import emojify from '../emoji';
 import escapeTextContentForBrowser from 'escape-html';
 import ImmutablePureComponent from 'react-immutable-pure-component';
 import scheduleIdleTask from '../features/ui/util/schedule_idle_task';
+import { MediaGallery, VideoPlayer } from '../features/ui/util/async-components';
+
+// We use the component (and not the container) since we do not want
+// to use the progress bar to show download progress
+import Bundle from '../features/ui/components/bundle';
 
 export default class Status extends ImmutablePureComponent {
 
@@ -154,6 +157,14 @@ export default class Status extends ImmutablePureComponent {
     this.setState({ isExpanded: !this.state.isExpanded });
   };
 
+  renderLoadingMediaGallery () {
+    return <div className='media_gallery' style={{ height: '110px' }} />;
+  }
+
+  renderLoadingVideoPlayer () {
+    return <div className='media-spoiler-video' style={{ height: '110px' }} />;
+  }
+
   render () {
     let media = null;
     let statusAvatar;
@@ -201,9 +212,17 @@ export default class Status extends ImmutablePureComponent {
       if (status.get('media_attachments').some(item => item.get('type') === 'unknown')) {
 
       } else if (status.getIn(['media_attachments', 0, 'type']) === 'video') {
-        media = <VideoPlayer media={status.getIn(['media_attachments', 0])} sensitive={status.get('sensitive')} onOpenVideo={this.props.onOpenVideo} />;
+        media = (
+          <Bundle fetchComponent={VideoPlayer} loading={this.renderLoadingVideoPlayer} onRender={this.saveHeight} >
+            {Component => <Component media={status.getIn(['media_attachments', 0])} sensitive={status.get('sensitive')} onOpenVideo={this.props.onOpenVideo} />}
+          </Bundle>
+        );
       } else {
-        media = <MediaGallery media={status.get('media_attachments')} sensitive={status.get('sensitive')} height={110} onOpenMedia={this.props.onOpenMedia} autoPlayGif={this.props.autoPlayGif} />;
+        media = (
+          <Bundle fetchComponent={MediaGallery} loading={this.renderLoadingMediaGallery} onRender={this.saveHeight} >
+            {Component => <Component media={status.get('media_attachments')} sensitive={status.get('sensitive')} height={110} onOpenMedia={this.props.onOpenMedia} autoPlayGif={this.props.autoPlayGif} />}
+          </Bundle>
+        );
       }
     }
 
diff --git a/app/javascript/mastodon/containers/mastodon.js b/app/javascript/mastodon/containers/mastodon.js
index 3bd89902f..6e79f9e4f 100644
--- a/app/javascript/mastodon/containers/mastodon.js
+++ b/app/javascript/mastodon/containers/mastodon.js
@@ -22,9 +22,10 @@ import { getLocale } from '../locales';
 const { localeData, messages } = getLocale();
 addLocaleData(localeData);
 
-const store = configureStore();
+export const store = configureStore();
 const initialState = JSON.parse(document.getElementById('initial-state').textContent);
-store.dispatch(hydrateStore(initialState));
+export const hydrateAction = hydrateStore(initialState);
+store.dispatch(hydrateAction);
 
 export default class Mastodon extends React.PureComponent {
 
diff --git a/app/javascript/mastodon/features/compose/components/emoji_picker_dropdown.js b/app/javascript/mastodon/features/compose/components/emoji_picker_dropdown.js
index c83dbb63e..83c66a5d5 100644
--- a/app/javascript/mastodon/features/compose/components/emoji_picker_dropdown.js
+++ b/app/javascript/mastodon/features/compose/components/emoji_picker_dropdown.js
@@ -2,6 +2,7 @@ import React from 'react';
 import Dropdown, { DropdownTrigger, DropdownContent } from 'react-simple-dropdown';
 import PropTypes from 'prop-types';
 import { defineMessages, injectIntl } from 'react-intl';
+import { EmojiPicker as EmojiPickerAsync } from '../../ui/util/async-components';
 
 const messages = defineMessages({
   emoji: { id: 'emoji_button.label', defaultMessage: 'Insert emoji' },
@@ -50,7 +51,7 @@ export default class EmojiPickerDropdown extends React.PureComponent {
     this.setState({ active: true });
     if (!EmojiPicker) {
       this.setState({ loading: true });
-      import(/* webpackChunkName: "emojione_picker" */ 'emojione-picker').then(TheEmojiPicker => {
+      EmojiPickerAsync().then(TheEmojiPicker => {
         EmojiPicker = TheEmojiPicker.default;
         this.setState({ loading: false });
       }).catch(() => {
diff --git a/app/javascript/mastodon/features/ui/components/bundle.js b/app/javascript/mastodon/features/ui/components/bundle.js
new file mode 100644
index 000000000..e69a32f47
--- /dev/null
+++ b/app/javascript/mastodon/features/ui/components/bundle.js
@@ -0,0 +1,96 @@
+import React from 'react';
+import PropTypes from 'prop-types';
+
+const emptyComponent = () => null;
+const noop = () => { };
+
+class Bundle extends React.Component {
+
+  static propTypes = {
+    fetchComponent: PropTypes.func.isRequired,
+    loading: PropTypes.func,
+    error: PropTypes.func,
+    children: PropTypes.func.isRequired,
+    renderDelay: PropTypes.number,
+    onRender: PropTypes.func,
+    onFetch: PropTypes.func,
+    onFetchSuccess: PropTypes.func,
+    onFetchFail: PropTypes.func,
+  }
+
+  static defaultProps = {
+    loading: emptyComponent,
+    error: emptyComponent,
+    renderDelay: 0,
+    onRender: noop,
+    onFetch: noop,
+    onFetchSuccess: noop,
+    onFetchFail: noop,
+  }
+
+  state = {
+    mod: undefined,
+    forceRender: false,
+  }
+
+  componentWillMount() {
+    this.load(this.props);
+  }
+
+  componentWillReceiveProps(nextProps) {
+    if (nextProps.fetchComponent !== this.props.fetchComponent) {
+      this.load(nextProps);
+    }
+  }
+
+  componentDidUpdate () {
+    this.props.onRender();
+  }
+
+  componentWillUnmount () {
+    if (this.timeout) {
+      clearTimeout(this.timeout);
+    }
+  }
+
+  load = (props) => {
+    const { fetchComponent, onFetch, onFetchSuccess, onFetchFail, renderDelay } = props || this.props;
+
+    this.setState({ mod: undefined });
+    onFetch();
+
+    if (renderDelay !== 0) {
+      this.timestamp = new Date();
+      this.timeout = setTimeout(() => this.setState({ forceRender: true }), renderDelay);
+    }
+
+    return fetchComponent()
+      .then((mod) => {
+        this.setState({ mod: mod.default });
+        onFetchSuccess();
+      })
+      .catch((error) => {
+        this.setState({ mod: null });
+        onFetchFail(error);
+      });
+  }
+
+  render() {
+    const { loading: Loading, error: Error, children, renderDelay } = this.props;
+    const { mod, forceRender } = this.state;
+    const elapsed = this.timestamp ? (new Date() - this.timestamp) : renderDelay;
+
+    if (mod === undefined) {
+      return (elapsed >= renderDelay || forceRender) ? <Loading /> : null;
+    }
+
+    if (mod === null) {
+      return <Error onRetry={this.load} />;
+    }
+
+    return children(mod);
+  }
+
+}
+
+export default Bundle;
diff --git a/app/javascript/mastodon/features/ui/components/bundle_column_error.js b/app/javascript/mastodon/features/ui/components/bundle_column_error.js
new file mode 100644
index 000000000..cd124746a
--- /dev/null
+++ b/app/javascript/mastodon/features/ui/components/bundle_column_error.js
@@ -0,0 +1,44 @@
+import React from 'react';
+import PropTypes from 'prop-types';
+import { defineMessages, injectIntl } from 'react-intl';
+
+import Column from './column';
+import ColumnHeader from './column_header';
+import ColumnBackButtonSlim from '../../../components/column_back_button_slim';
+import IconButton from '../../../components/icon_button';
+
+const messages = defineMessages({
+  title: { id: 'bundle_column_error.title', defaultMessage: 'Network error' },
+  body: { id: 'bundle_column_error.body', defaultMessage: 'Something went wrong while loading this component.' },
+  retry: { id: 'bundle_column_error.retry', defaultMessage: 'Try again' },
+});
+
+class BundleColumnError extends React.Component {
+
+  static propTypes = {
+    onRetry: PropTypes.func.isRequired,
+    intl: PropTypes.object.isRequired,
+  }
+
+  handleRetry = () => {
+    this.props.onRetry();
+  }
+
+  render () {
+    const { intl: { formatMessage } } = this.props;
+
+    return (
+      <Column>
+        <ColumnHeader icon='exclamation-circle' type={formatMessage(messages.title)} />
+        <ColumnBackButtonSlim />
+        <div className='error-column'>
+          <IconButton title={formatMessage(messages.retry)} icon='refresh' onClick={this.handleRetry} size={64} />
+          {formatMessage(messages.body)}
+        </div>
+      </Column>
+    );
+  }
+
+}
+
+export default injectIntl(BundleColumnError);
diff --git a/app/javascript/mastodon/features/ui/components/bundle_modal_error.js b/app/javascript/mastodon/features/ui/components/bundle_modal_error.js
new file mode 100644
index 000000000..928bfe1f7
--- /dev/null
+++ b/app/javascript/mastodon/features/ui/components/bundle_modal_error.js
@@ -0,0 +1,53 @@
+import React from 'react';
+import PropTypes from 'prop-types';
+import { defineMessages, injectIntl } from 'react-intl';
+
+import IconButton from '../../../components/icon_button';
+
+const messages = defineMessages({
+  error: { id: 'bundle_modal_error.message', defaultMessage: 'Something went wrong while loading this component.' },
+  retry: { id: 'bundle_modal_error.retry', defaultMessage: 'Try again' },
+  close: { id: 'bundle_modal_error.close', defaultMessage: 'Close' },
+});
+
+class BundleModalError extends React.Component {
+
+  static propTypes = {
+    onRetry: PropTypes.func.isRequired,
+    onClose: PropTypes.func.isRequired,
+    intl: PropTypes.object.isRequired,
+  }
+
+  handleRetry = () => {
+    this.props.onRetry();
+  }
+
+  render () {
+    const { onClose, intl: { formatMessage } } = this.props;
+
+    // Keep the markup in sync with <ModalLoading />
+    // (make sure they have the same dimensions)
+    return (
+      <div className='modal-root__modal error-modal'>
+        <div className='error-modal__body'>
+          <IconButton title={formatMessage(messages.retry)} icon='refresh' onClick={this.handleRetry} size={64} />
+          {formatMessage(messages.error)}
+        </div>
+
+        <div className='error-modal__footer'>
+          <div>
+            <button
+              onClick={onClose}
+              className='error-modal__nav onboarding-modal__skip'
+            >
+              {formatMessage(messages.close)}
+            </button>
+          </div>
+        </div>
+      </div>
+    );
+  }
+
+}
+
+export default injectIntl(BundleModalError);
diff --git a/app/javascript/mastodon/features/ui/components/column_loading.js b/app/javascript/mastodon/features/ui/components/column_loading.js
new file mode 100644
index 000000000..9bb9c14a1
--- /dev/null
+++ b/app/javascript/mastodon/features/ui/components/column_loading.js
@@ -0,0 +1,13 @@
+import React from 'react';
+
+import Column from '../../../components/column';
+import ColumnHeader from '../../../components/column_header';
+
+const ColumnLoading = () => (
+  <Column>
+    <ColumnHeader icon=' ' title='' multiColumn={false} />
+    <div className='scrollable' />
+  </Column>
+);
+
+export default ColumnLoading;
diff --git a/app/javascript/mastodon/features/ui/components/columns_area.js b/app/javascript/mastodon/features/ui/components/columns_area.js
index 01167b6e5..5fa27599f 100644
--- a/app/javascript/mastodon/features/ui/components/columns_area.js
+++ b/app/javascript/mastodon/features/ui/components/columns_area.js
@@ -2,15 +2,15 @@ import React from 'react';
 import PropTypes from 'prop-types';
 import ImmutablePropTypes from 'react-immutable-proptypes';
 import ImmutablePureComponent from 'react-immutable-pure-component';
+
 import ReactSwipeable from 'react-swipeable';
-import HomeTimeline from '../../home_timeline';
-import Notifications from '../../notifications';
-import PublicTimeline from '../../public_timeline';
-import CommunityTimeline from '../../community_timeline';
-import HashtagTimeline from '../../hashtag_timeline';
-import Compose from '../../compose';
 import { getPreviousLink, getNextLink } from './tabs_bar';
 
+import BundleContainer from '../containers/bundle_container';
+import ColumnLoading from './column_loading';
+import BundleColumnError from './bundle_column_error';
+import { Compose, Notifications, HomeTimeline, CommunityTimeline, PublicTimeline, HashtagTimeline } from '../../ui/util/async-components';
+
 const componentMap = {
   'COMPOSE': Compose,
   'HOME': HomeTimeline,
@@ -48,6 +48,14 @@ export default class ColumnsArea extends ImmutablePureComponent {
     }
   };
 
+  renderLoading = () => {
+    return <ColumnLoading />;
+  }
+
+  renderError = (props) => {
+    return <BundleColumnError {...props} />;
+  }
+
   render () {
     const { columns, children, singleColumn } = this.props;
 
@@ -62,9 +70,13 @@ export default class ColumnsArea extends ImmutablePureComponent {
     return (
       <div className='columns-area'>
         {columns.map(column => {
-          const SpecificComponent = componentMap[column.get('id')];
           const params = column.get('params', null) === null ? null : column.get('params').toJS();
-          return <SpecificComponent key={column.get('uuid')} columnId={column.get('uuid')} params={params} multiColumn />;
+
+          return (
+            <BundleContainer key={column.get('uuid')} fetchComponent={componentMap[column.get('id')]} loading={this.renderLoading} error={this.renderError}>
+              {SpecificComponent => <SpecificComponent columnId={column.get('uuid')} params={params} multiColumn />}
+            </BundleContainer>
+          );
         })}
 
         {React.Children.map(children, child => React.cloneElement(child, { multiColumn: true }))}
diff --git a/app/javascript/mastodon/features/ui/components/modal_loading.js b/app/javascript/mastodon/features/ui/components/modal_loading.js
new file mode 100644
index 000000000..f403ca4c9
--- /dev/null
+++ b/app/javascript/mastodon/features/ui/components/modal_loading.js
@@ -0,0 +1,20 @@
+import React from 'react';
+
+import LoadingIndicator from '../../../components/loading_indicator';
+
+// Keep the markup in sync with <BundleModalError />
+// (make sure they have the same dimensions)
+const ModalLoading = () => (
+  <div className='modal-root__modal error-modal'>
+    <div className='error-modal__body'>
+      <LoadingIndicator />
+    </div>
+    <div className='error-modal__footer'>
+      <div>
+        <button className='error-modal__nav onboarding-modal__skip' />
+      </div>
+    </div>
+  </div>
+);
+
+export default ModalLoading;
diff --git a/app/javascript/mastodon/features/ui/components/modal_root.js b/app/javascript/mastodon/features/ui/components/modal_root.js
index 48b048eb7..085299038 100644
--- a/app/javascript/mastodon/features/ui/components/modal_root.js
+++ b/app/javascript/mastodon/features/ui/components/modal_root.js
@@ -1,13 +1,18 @@
 import React from 'react';
 import PropTypes from 'prop-types';
-import MediaModal from './media_modal';
-import OnboardingModal from './onboarding_modal';
-import VideoModal from './video_modal';
-import BoostModal from './boost_modal';
-import ConfirmationModal from './confirmation_modal';
-import ReportModal from './report_modal';
 import TransitionMotion from 'react-motion/lib/TransitionMotion';
 import spring from 'react-motion/lib/spring';
+import BundleContainer from '../containers/bundle_container';
+import BundleModalError from './bundle_modal_error';
+import ModalLoading from './modal_loading';
+import {
+  MediaModal,
+  OnboardingModal,
+  VideoModal,
+  BoostModal,
+  ConfirmationModal,
+  ReportModal,
+} from '../../../features/ui/util/async-components';
 
 const MODAL_COMPONENTS = {
   'MEDIA': MediaModal,
@@ -49,6 +54,22 @@ export default class ModalRoot extends React.PureComponent {
     return { opacity: spring(0), scale: spring(0.98) };
   }
 
+  renderModal = (SpecificComponent) => {
+    const { props, onClose } = this.props;
+
+    return <SpecificComponent {...props} onClose={onClose} />;
+  }
+
+  renderLoading = () => {
+    return <ModalLoading />;
+  }
+
+  renderError = (props) => {
+    const { onClose } = this.props;
+
+    return <BundleModalError {...props} onClose={onClose} />;
+  }
+
   render () {
     const { type, props, onClose } = this.props;
     const visible = !!type;
@@ -70,18 +91,14 @@ export default class ModalRoot extends React.PureComponent {
       >
         {interpolatedStyles =>
           <div className='modal-root'>
-            {interpolatedStyles.map(({ key, data: { type, props }, style }) => {
-              const SpecificComponent = MODAL_COMPONENTS[type];
-
-              return (
-                <div key={key} style={{ pointerEvents: visible ? 'auto' : 'none' }}>
-                  <div role='presentation' className='modal-root__overlay' style={{ opacity: style.opacity }} onClick={onClose} />
-                  <div className='modal-root__container' style={{ opacity: style.opacity, transform: `translateZ(0px) scale(${style.scale})` }}>
-                    <SpecificComponent {...props} onClose={onClose} />
-                  </div>
+            {interpolatedStyles.map(({ key, data: { type }, style }) => (
+              <div key={key} style={{ pointerEvents: visible ? 'auto' : 'none' }}>
+                <div role='presentation' className='modal-root__overlay' style={{ opacity: style.opacity }} onClick={onClose} />
+                <div className='modal-root__container' style={{ opacity: style.opacity, transform: `translateZ(0px) scale(${style.scale})` }}>
+                  <BundleContainer fetchComponent={MODAL_COMPONENTS[type]} loading={this.renderLoading} error={this.renderError} renderDelay={200}>{this.renderModal}</BundleContainer>
                 </div>
-              );
-            })}
+              </div>
+            ))}
           </div>
         }
       </TransitionMotion>
diff --git a/app/javascript/mastodon/features/ui/containers/bundle_container.js b/app/javascript/mastodon/features/ui/containers/bundle_container.js
new file mode 100644
index 000000000..7e3f0c3a6
--- /dev/null
+++ b/app/javascript/mastodon/features/ui/containers/bundle_container.js
@@ -0,0 +1,19 @@
+import { connect } from 'react-redux';
+
+import Bundle from '../components/bundle';
+
+import { fetchBundleRequest, fetchBundleSuccess, fetchBundleFail } from '../../../actions/bundles';
+
+const mapDispatchToProps = dispatch => ({
+  onFetch () {
+    dispatch(fetchBundleRequest());
+  },
+  onFetchSuccess () {
+    dispatch(fetchBundleSuccess());
+  },
+  onFetchFail (error) {
+    dispatch(fetchBundleFail(error));
+  },
+});
+
+export default connect(null, mapDispatchToProps)(Bundle);
diff --git a/app/javascript/mastodon/features/ui/index.js b/app/javascript/mastodon/features/ui/index.js
index 54e623d99..6057d8797 100644
--- a/app/javascript/mastodon/features/ui/index.js
+++ b/app/javascript/mastodon/features/ui/index.js
@@ -1,7 +1,5 @@
 import React from 'react';
 import classNames from 'classnames';
-import Switch from 'react-router-dom/Switch';
-import Route from 'react-router-dom/Route';
 import Redirect from 'react-router-dom/Redirect';
 import NotificationsContainer from './containers/notifications_container';
 import PropTypes from 'prop-types';
@@ -14,64 +12,40 @@ import { debounce } from 'lodash';
 import { uploadCompose } from '../../actions/compose';
 import { refreshHomeTimeline } from '../../actions/timelines';
 import { refreshNotifications } from '../../actions/notifications';
+import { WrappedSwitch, WrappedRoute } from './util/react_router_helpers';
 import UploadArea from './components/upload_area';
+import { store } from '../../containers/mastodon';
 import ColumnsAreaContainer from './containers/columns_area_container';
-import Status from '../../features/status';
-import GettingStarted from '../../features/getting_started';
-import PublicTimeline from '../../features/public_timeline';
-import CommunityTimeline from '../../features/community_timeline';
-import AccountTimeline from '../../features/account_timeline';
-import AccountGallery from '../../features/account_gallery';
-import HomeTimeline from '../../features/home_timeline';
-import Compose from '../../features/compose';
-import Followers from '../../features/followers';
-import Following from '../../features/following';
-import Reblogs from '../../features/reblogs';
-import Favourites from '../../features/favourites';
-import HashtagTimeline from '../../features/hashtag_timeline';
-import Notifications from '../../features/notifications';
-import FollowRequests from '../../features/follow_requests';
-import GenericNotFound from '../../features/generic_not_found';
-import FavouritedStatuses from '../../features/favourited_statuses';
-import Blocks from '../../features/blocks';
-import Mutes from '../../features/mutes';
-
-// Small wrapper to pass multiColumn to the route components
-const WrappedSwitch = ({ multiColumn, children }) => (
-  <Switch>
-    {React.Children.map(children, child => React.cloneElement(child, { multiColumn }))}
-  </Switch>
-);
-
-WrappedSwitch.propTypes = {
-  multiColumn: PropTypes.bool,
-  children: PropTypes.node,
-};
-
-// Small Wraper to extract the params from the route and pass
-// them to the rendered component, together with the content to
-// be rendered inside (the children)
-class WrappedRoute extends React.Component {
-
-  static propTypes = {
-    component: PropTypes.func.isRequired,
-    content: PropTypes.node,
-    multiColumn: PropTypes.bool,
-  }
-
-  renderComponent = ({ match: { params } }) => {
-    const { component: Component, content, multiColumn } = this.props;
-
-    return <Component params={params} multiColumn={multiColumn}>{content}</Component>;
-  }
-
-  render () {
-    const { component: Component, content, ...rest } = this.props;
-
-    return <Route {...rest} render={this.renderComponent} />;
-  }
+import {
+  Compose,
+  Status,
+  GettingStarted,
+  PublicTimeline,
+  CommunityTimeline,
+  AccountTimeline,
+  AccountGallery,
+  HomeTimeline,
+  Followers,
+  Following,
+  Reblogs,
+  Favourites,
+  HashtagTimeline,
+  Notifications as AsyncNotifications,
+  FollowRequests,
+  GenericNotFound,
+  FavouritedStatuses,
+  Blocks,
+  Mutes,
+} from './util/async-components';
+
+const Notifications = () => AsyncNotifications().then(component => {
+  store.dispatch(refreshNotifications());
+  return component;
+});
 
-}
+// Dummy import, to make sure that <Status /> ends up in the application bundle.
+// Without this it ends up in ~8 very commonly used bundles.
+import '../../components/status';
 
 const mapStateToProps = state => ({
   systemFontUi: state.getIn(['meta', 'system_font_ui']),
@@ -162,7 +136,6 @@ export default class UI extends React.PureComponent {
     document.addEventListener('dragend', this.handleDragEnd, false);
 
     this.props.dispatch(refreshHomeTimeline());
-    this.props.dispatch(refreshNotifications());
   }
 
   componentWillUnmount () {
diff --git a/app/javascript/mastodon/features/ui/util/async-components.js b/app/javascript/mastodon/features/ui/util/async-components.js
new file mode 100644
index 000000000..c9f81136d
--- /dev/null
+++ b/app/javascript/mastodon/features/ui/util/async-components.js
@@ -0,0 +1,143 @@
+import { store } from '../../../containers/mastodon';
+import { injectAsyncReducer } from '../../../store/configureStore';
+
+// NOTE: When lazy-loading reducers, make sure to add them
+// to application.html.haml (if the component is preloaded there)
+
+export function EmojiPicker () {
+  return import(/* webpackChunkName: "emojione_picker" */'emojione-picker');
+}
+
+export function Compose () {
+  return Promise.all([
+    import(/* webpackChunkName: "features/compose" */'../../compose'),
+    import(/* webpackChunkName: "reducers/compose" */'../../../reducers/compose'),
+    import(/* webpackChunkName: "reducers/media_attachments" */'../../../reducers/media_attachments'),
+    import(/* webpackChunkName: "reducers/search" */'../../../reducers/search'),
+  ]).then(([component, composeReducer, mediaAttachmentsReducer, searchReducer]) => {
+    injectAsyncReducer(store, 'compose', composeReducer.default);
+    injectAsyncReducer(store, 'media_attachments', mediaAttachmentsReducer.default);
+    injectAsyncReducer(store, 'search', searchReducer.default);
+
+    return component;
+  });
+}
+
+export function Notifications () {
+  return Promise.all([
+    import(/* webpackChunkName: "features/notifications" */'../../notifications'),
+    import(/* webpackChunkName: "reducers/notifications" */'../../../reducers/notifications'),
+  ]).then(([component, notificationsReducer]) => {
+    injectAsyncReducer(store, 'notifications', notificationsReducer.default);
+
+    return component;
+  });
+}
+
+export function HomeTimeline () {
+  return import(/* webpackChunkName: "features/home_timeline" */'../../home_timeline');
+}
+
+export function PublicTimeline () {
+  return import(/* webpackChunkName: "features/public_timeline" */'../../public_timeline');
+}
+
+export function CommunityTimeline () {
+  return import(/* webpackChunkName: "features/community_timeline" */'../../community_timeline');
+}
+
+export function HashtagTimeline () {
+  return import(/* webpackChunkName: "features/hashtag_timeline" */'../../hashtag_timeline');
+}
+
+export function Status () {
+  return import(/* webpackChunkName: "features/status" */'../../status');
+}
+
+export function GettingStarted () {
+  return import(/* webpackChunkName: "features/getting_started" */'../../getting_started');
+}
+
+export function AccountTimeline () {
+  return import(/* webpackChunkName: "features/account_timeline" */'../../account_timeline');
+}
+
+export function AccountGallery () {
+  return import(/* webpackChunkName: "features/account_gallery" */'../../account_gallery');
+}
+
+export function Followers () {
+  return import(/* webpackChunkName: "features/followers" */'../../followers');
+}
+
+export function Following () {
+  return import(/* webpackChunkName: "features/following" */'../../following');
+}
+
+export function Reblogs () {
+  return import(/* webpackChunkName: "features/reblogs" */'../../reblogs');
+}
+
+export function Favourites () {
+  return import(/* webpackChunkName: "features/favourites" */'../../favourites');
+}
+
+export function FollowRequests () {
+  return import(/* webpackChunkName: "features/follow_requests" */'../../follow_requests');
+}
+
+export function GenericNotFound () {
+  return import(/* webpackChunkName: "features/generic_not_found" */'../../generic_not_found');
+}
+
+export function FavouritedStatuses () {
+  return import(/* webpackChunkName: "features/favourited_statuses" */'../../favourited_statuses');
+}
+
+export function Blocks () {
+  return import(/* webpackChunkName: "features/blocks" */'../../blocks');
+}
+
+export function Mutes () {
+  return import(/* webpackChunkName: "features/mutes" */'../../mutes');
+}
+
+export function MediaModal () {
+  return import(/* webpackChunkName: "modals/media_modal" */'../components/media_modal');
+}
+
+export function OnboardingModal () {
+  return Promise.all([
+    import(/* webpackChunkName: "modals/onboarding_modal" */'../components/onboarding_modal'),
+    import(/* webpackChunkName: "reducers/compose" */'../../../reducers/compose'),
+    import(/* webpackChunkName: "reducers/media_attachments" */'../../../reducers/media_attachments'),
+  ]).then(([component, composeReducer, mediaAttachmentsReducer]) => {
+    injectAsyncReducer(store, 'compose', composeReducer.default);
+    injectAsyncReducer(store, 'media_attachments', mediaAttachmentsReducer.default);
+    return component;
+  });
+}
+
+export function VideoModal () {
+  return import(/* webpackChunkName: "modals/video_modal" */'../components/video_modal');
+}
+
+export function BoostModal () {
+  return import(/* webpackChunkName: "modals/boost_modal" */'../components/boost_modal');
+}
+
+export function ConfirmationModal () {
+  return import(/* webpackChunkName: "modals/confirmation_modal" */'../components/confirmation_modal');
+}
+
+export function ReportModal () {
+  return import(/* webpackChunkName: "modals/report_modal" */'../components/report_modal');
+}
+
+export function MediaGallery () {
+  return import(/* webpackChunkName: "status/MediaGallery" */'../../../components/media_gallery');
+}
+
+export function VideoPlayer () {
+  return import(/* webpackChunkName: "status/VideoPlayer" */'../../../components/video_player');
+}
diff --git a/app/javascript/mastodon/features/ui/util/react_router_helpers.js b/app/javascript/mastodon/features/ui/util/react_router_helpers.js
new file mode 100644
index 000000000..e33a6df6f
--- /dev/null
+++ b/app/javascript/mastodon/features/ui/util/react_router_helpers.js
@@ -0,0 +1,65 @@
+import React from 'react';
+import PropTypes from 'prop-types';
+import Switch from 'react-router-dom/Switch';
+import Route from 'react-router-dom/Route';
+
+import ColumnLoading from '../components/column_loading';
+import BundleColumnError from '../components/bundle_column_error';
+import BundleContainer from '../containers/bundle_container';
+
+// Small wrapper to pass multiColumn to the route components
+export const WrappedSwitch = ({ multiColumn, children }) => (
+  <Switch>
+    {React.Children.map(children, child => React.cloneElement(child, { multiColumn }))}
+  </Switch>
+);
+
+WrappedSwitch.propTypes = {
+  multiColumn: PropTypes.bool,
+  children: PropTypes.node,
+};
+
+// Small Wraper to extract the params from the route and pass
+// them to the rendered component, together with the content to
+// be rendered inside (the children)
+export class WrappedRoute extends React.Component {
+
+  static propTypes = {
+    component: PropTypes.func.isRequired,
+    content: PropTypes.node,
+    multiColumn: PropTypes.bool,
+  }
+
+  renderComponent = ({ match }) => {
+    this.match = match; // Needed for this.renderBundle
+
+    const { component } = this.props;
+
+    return (
+      <BundleContainer fetchComponent={component} loading={this.renderLoading} error={this.renderError}>
+        {this.renderBundle}
+      </BundleContainer>
+    );
+  }
+
+  renderLoading = () => {
+    return <ColumnLoading />;
+  }
+
+  renderError = (props) => {
+    return <BundleColumnError {...props} />;
+  }
+
+  renderBundle = (Component) => {
+    const { match: { params }, props: { content, multiColumn } } = this;
+
+    return <Component params={params} multiColumn={multiColumn}>{content}</Component>;
+  }
+
+  render () {
+    const { component: Component, content, ...rest } = this.props;
+
+    return <Route {...rest} render={this.renderComponent} />;
+  }
+
+}
diff --git a/app/javascript/mastodon/reducers/compose.js b/app/javascript/mastodon/reducers/compose.js
index d0b47a85c..09db95e2d 100644
--- a/app/javascript/mastodon/reducers/compose.js
+++ b/app/javascript/mastodon/reducers/compose.js
@@ -23,7 +23,7 @@ import {
   COMPOSE_EMOJI_INSERT,
 } from '../actions/compose';
 import { TIMELINE_DELETE } from '../actions/timelines';
-import { STORE_HYDRATE } from '../actions/store';
+import { STORE_HYDRATE_LAZY } from '../actions/store';
 import Immutable from 'immutable';
 import uuid from '../uuid';
 
@@ -134,7 +134,7 @@ const privacyPreference = (a, b) => {
 
 export default function compose(state = initialState, action) {
   switch(action.type) {
-  case STORE_HYDRATE:
+  case `${STORE_HYDRATE_LAZY}-compose`:
     return clearAll(state.merge(action.state.get('compose')));
   case COMPOSE_MOUNT:
     return state.set('mounted', true);
diff --git a/app/javascript/mastodon/reducers/index.js b/app/javascript/mastodon/reducers/index.js
index be402a16b..79062f2f9 100644
--- a/app/javascript/mastodon/reducers/index.js
+++ b/app/javascript/mastodon/reducers/index.js
@@ -1,7 +1,6 @@
 import { combineReducers } from 'redux-immutable';
 import timelines from './timelines';
 import meta from './meta';
-import compose from './compose';
 import alerts from './alerts';
 import { loadingBarReducer } from 'react-redux-loading-bar';
 import modal from './modal';
@@ -9,20 +8,16 @@ import user_lists from './user_lists';
 import accounts from './accounts';
 import accounts_counters from './accounts_counters';
 import statuses from './statuses';
-import media_attachments from './media_attachments';
 import relationships from './relationships';
-import search from './search';
-import notifications from './notifications';
 import settings from './settings';
 import status_lists from './status_lists';
 import cards from './cards';
 import reports from './reports';
 import contexts from './contexts';
 
-export default combineReducers({
+const reducers = {
   timelines,
   meta,
-  compose,
   alerts,
   loadingBar: loadingBarReducer,
   modal,
@@ -30,13 +25,19 @@ export default combineReducers({
   status_lists,
   accounts,
   accounts_counters,
-  media_attachments,
   statuses,
   relationships,
-  search,
-  notifications,
   settings,
   cards,
   reports,
   contexts,
-});
+};
+
+export function createReducer(asyncReducers) {
+  return combineReducers({
+    ...reducers,
+    ...asyncReducers,
+  });
+}
+
+export default combineReducers(reducers);
diff --git a/app/javascript/mastodon/reducers/media_attachments.js b/app/javascript/mastodon/reducers/media_attachments.js
index 85bea4f0b..d17d465aa 100644
--- a/app/javascript/mastodon/reducers/media_attachments.js
+++ b/app/javascript/mastodon/reducers/media_attachments.js
@@ -1,4 +1,4 @@
-import { STORE_HYDRATE } from '../actions/store';
+import { STORE_HYDRATE_LAZY } from '../actions/store';
 import Immutable from 'immutable';
 
 const initialState = Immutable.Map({
@@ -7,7 +7,7 @@ const initialState = Immutable.Map({
 
 export default function meta(state = initialState, action) {
   switch(action.type) {
-  case STORE_HYDRATE:
+  case `${STORE_HYDRATE_LAZY}-media_attachments`:
     return state.merge(action.state.get('media_attachments'));
   default:
     return state;
diff --git a/app/javascript/mastodon/store/configureStore.js b/app/javascript/mastodon/store/configureStore.js
index 1376d4cba..0fe29f031 100644
--- a/app/javascript/mastodon/store/configureStore.js
+++ b/app/javascript/mastodon/store/configureStore.js
@@ -1,15 +1,36 @@
 import { createStore, applyMiddleware, compose } from 'redux';
 import thunk from 'redux-thunk';
-import appReducer from '../reducers';
+import appReducer, { createReducer } from '../reducers';
+import { hydrateStoreLazy } from '../actions/store';
+import { hydrateAction } from '../containers/mastodon';
 import loadingBarMiddleware from '../middleware/loading_bar';
 import errorsMiddleware from '../middleware/errors';
 import soundsMiddleware from '../middleware/sounds';
 
 export default function configureStore() {
-  return createStore(appReducer, compose(applyMiddleware(
+  const store = createStore(appReducer, compose(applyMiddleware(
     thunk,
     loadingBarMiddleware({ promiseTypeSuffixes: ['REQUEST', 'SUCCESS', 'FAIL'] }),
     errorsMiddleware(),
     soundsMiddleware()
   ), window.devToolsExtension ? window.devToolsExtension() : f => f));
+
+  store.asyncReducers = { };
+
+  return store;
 };
+
+export function injectAsyncReducer(store, name, asyncReducer) {
+  if (!store.asyncReducers[name]) {
+    // Keep track that we injected this reducer
+    store.asyncReducers[name] = asyncReducer;
+
+    // Add the current reducer to the store
+    store.replaceReducer(createReducer(store.asyncReducers));
+
+    // The state this reducer handles defaults to its initial state (stored inside the reducer)
+    // But that state may be out of date because of the server-side hydration, so we replay
+    // the hydration action but only for this reducer (all async reducers must listen for this dynamic action)
+    store.dispatch(hydrateStoreLazy(name, hydrateAction.state));
+  }
+}
diff --git a/app/javascript/styles/components.scss b/app/javascript/styles/components.scss
index a87aa5d79..9b500c7ad 100644
--- a/app/javascript/styles/components.scss
+++ b/app/javascript/styles/components.scss
@@ -2300,7 +2300,8 @@ button.icon-button.active i.fa-retweet {
   vertical-align: middle;
 }
 
-.empty-column-indicator {
+.empty-column-indicator,
+.error-column {
   color: lighten($ui-base-color, 20%);
   background: $ui-base-color;
   text-align: center;
@@ -2326,6 +2327,10 @@ button.icon-button.active i.fa-retweet {
   }
 }
 
+.error-column {
+  flex-direction: column;
+}
+
 @keyframes pulse {
   0% {
     opacity: 1;
@@ -2909,7 +2914,8 @@ button.icon-button.active i.fa-retweet {
   z-index: 100;
 }
 
-.onboarding-modal {
+.onboarding-modal,
+.error-modal {
   background: $ui-secondary-color;
   color: $ui-base-color;
   border-radius: 8px;
@@ -2918,7 +2924,8 @@ button.icon-button.active i.fa-retweet {
   flex-direction: column;
 }
 
-.onboarding-modal__pager {
+.onboarding-modal__pager,
+.error-modal__body {
   height: 80vh;
   width: 80vw;
   max-width: 520px;
@@ -2943,6 +2950,14 @@ button.icon-button.active i.fa-retweet {
   }
 }
 
+.error-modal__body {
+  display: flex;
+  flex-direction: column;
+  justify-content: center;
+  align-items: center;
+  text-align: center;
+}
+
 @media screen and (max-width: 550px) {
   .onboarding-modal {
     width: 100%;
@@ -2959,7 +2974,8 @@ button.icon-button.active i.fa-retweet {
   }
 }
 
-.onboarding-modal__paginator {
+.onboarding-modal__paginator,
+.error-modal__footer {
   flex: 0 0 auto;
   background: darken($ui-secondary-color, 8%);
   display: flex;
@@ -2969,7 +2985,8 @@ button.icon-button.active i.fa-retweet {
     min-width: 33px;
   }
 
-  .onboarding-modal__nav {
+  .onboarding-modal__nav,
+  .error-modal__nav {
     color: darken($ui-secondary-color, 34%);
     background-color: transparent;
     border: 0;
@@ -2992,6 +3009,10 @@ button.icon-button.active i.fa-retweet {
   }
 }
 
+.error-modal__footer {
+  justify-content: center;
+}
+
 .onboarding-modal__dots {
   flex: 1 1 auto;
   display: flex;
diff --git a/app/views/layouts/application.html.haml b/app/views/layouts/application.html.haml
index f991bc74f..68d346859 100755
--- a/app/views/layouts/application.html.haml
+++ b/app/views/layouts/application.html.haml
@@ -20,6 +20,23 @@
 
     = stylesheet_pack_tag 'application', media: 'all'
     = javascript_pack_tag 'common', integrity: true, crossorigin: 'anonymous'
+
+    = javascript_pack_tag 'features/getting_started', integrity: true, crossorigin: 'anonymous', rel: 'preload', as: 'script'
+
+    = javascript_pack_tag 'features/compose', integrity: true, crossorigin: 'anonymous', rel: 'preload', as: 'script'
+    = javascript_pack_tag 'reducers/compose', integrity: true, crossorigin: 'anonymous', rel: 'preload', as: 'script'
+    = javascript_pack_tag 'reducers/media_attachments', integrity: true, crossorigin: 'anonymous', rel: 'preload', as: 'script'
+    = javascript_pack_tag 'reducers/search', integrity: true, crossorigin: 'anonymous', rel: 'preload', as: 'script'
+
+    = javascript_pack_tag 'features/home_timeline', integrity: true, crossorigin: 'anonymous', rel: 'preload', as: 'script'
+
+    = javascript_pack_tag 'features/notifications', integrity: true, crossorigin: 'anonymous', rel: 'preload', as: 'script'
+    = javascript_pack_tag 'reducers/notifications', integrity: true, crossorigin: 'anonymous', rel: 'preload', as: 'script'
+
+    = javascript_pack_tag 'features/community_timeline', integrity: true, crossorigin: 'anonymous', rel: 'preload', as: 'script'
+
+    = javascript_pack_tag 'features/public_timeline', integrity: true, crossorigin: 'anonymous', rel: 'preload', as: 'script'
+
     = javascript_pack_tag "locale_#{I18n.locale}", integrity: true, crossorigin: 'anonymous'
     = csrf_meta_tags