Replace react-router-scroll-4 with inlined implementation (#36253)

app/javascript/mastodon/components/router.tsx

@@ -1,6 +1,7 @@
 import type { PropsWithChildren } from 'react';
 import type React from 'react';
 
+import type { useLocation } from 'react-router';
 import { Router as OriginalRouter, useHistory } from 'react-router';
 
 import type {
@@ -18,7 +19,9 @@ interface MastodonLocationState {
   mastodonModalKey?: string;
 }
 
-type LocationState = MastodonLocationState | null | undefined;
+export type LocationState = MastodonLocationState | null | undefined;
+
+export type MastodonLocation = ReturnType<typeof useLocation<LocationState>>;
 
 type HistoryPath = Path | LocationDescriptor<LocationState>;
 

app/javascript/mastodon/components/scrollable_list.jsx

@@ -10,7 +10,7 @@ import { connect } from 'react-redux';
 import { supportsPassiveEvents } from 'detect-passive-events';
 import { throttle } from 'lodash';
 
-import ScrollContainer from 'mastodon/containers/scroll_container';
+import { ScrollContainer } from 'mastodon/containers/scroll_container';
 
 import IntersectionObserverArticleContainer from '../containers/intersection_observer_article_container';
 import { attachFullscreenListener, detachFullscreenListener, isFullscreen } from '../features/ui/util/fullscreen';

app/javascript/mastodon/containers/mastodon.jsx

@@ -5,7 +5,6 @@ import { Route } from 'react-router-dom';
 
 import { Provider as ReduxProvider } from 'react-redux';
 
-import { ScrollContext } from 'react-router-scroll-4';
 
 import { fetchCustomEmojis } from 'mastodon/actions/custom_emojis';
 import { hydrateStore } from 'mastodon/actions/store';
@@ -20,6 +19,8 @@ import { store } from 'mastodon/store';
 import { isProduction } from 'mastodon/utils/environment';
 import { BodyScrollLock } from 'mastodon/features/ui/components/body_scroll_lock';
 
+import { ScrollContext } from './scroll_container/scroll_context';
+
 const title = isProduction() ? siteTitle : `${siteTitle} (Dev)`;
 
 const hydrateAction = hydrateStore(initialState);
@@ -45,10 +46,6 @@ export default class Mastodon extends PureComponent {
     }
   }
 
-  shouldUpdateScroll (prevRouterProps, { location }) {
-    return !(location.state?.mastodonModalKey && location.state?.mastodonModalKey !== prevRouterProps?.location?.state?.mastodonModalKey);
-  }
-
   render () {
     return (
       <IdentityContext.Provider value={this.identity}>
@@ -56,7 +53,7 @@ export default class Mastodon extends PureComponent {
           <ReduxProvider store={store}>
             <ErrorBoundary>
               <Router>
-                <ScrollContext shouldUpdateScroll={this.shouldUpdateScroll}>
+                <ScrollContext>
                   <Route path='/' component={UI} />
                 </ScrollContext>
                 <BodyScrollLock />

app/javascript/mastodon/containers/scroll_container.js

@@ -1,18 +0,0 @@
-import { ScrollContainer as OriginalScrollContainer } from 'react-router-scroll-4';
-
-// ScrollContainer is used to automatically scroll to the top when pushing a
-// new history state and remembering the scroll position when going back.
-// There are a few things we need to do differently, though.
-const defaultShouldUpdateScroll = (prevRouterProps, { location }) => {
-  // If the change is caused by opening a modal, do not scroll to top
-  return !(location.state?.mastodonModalKey && location.state?.mastodonModalKey !== prevRouterProps?.location?.state?.mastodonModalKey);
-};
-
-export default
-class ScrollContainer extends OriginalScrollContainer {
-
-  static defaultProps = {
-    shouldUpdateScroll: defaultShouldUpdateScroll,
-  };
-
-}

app/javascript/mastodon/containers/scroll_container/default_should_update_scroll.tsx

@@ -0,0 +1,25 @@
+import type { MastodonLocation } from 'mastodon/components/router';
+
+export type ShouldUpdateScrollFn = (
+  prevLocationContext: MastodonLocation | null,
+  locationContext: MastodonLocation,
+) => boolean;
+
+/**
+ * ScrollBehavior will automatically scroll to the top on navigations
+ * or restore saved scroll positions, but on some location changes we
+ * need to prevent this.
+ */
+
+export const defaultShouldUpdateScroll: ShouldUpdateScrollFn = (
+  prevLocation,
+  location,
+) => {
+  // If the change is caused by opening a modal, do not scroll to top
+  const shouldUpdateScroll = !(
+    location.state?.mastodonModalKey &&
+    location.state.mastodonModalKey !== prevLocation?.state?.mastodonModalKey
+  );
+
+  return shouldUpdateScroll;
+};

app/javascript/mastodon/containers/scroll_container/index.tsx

@@ -0,0 +1,62 @@
+import React, { useContext, useEffect, useRef } from 'react';
+
+import { defaultShouldUpdateScroll } from './default_should_update_scroll';
+import type { ShouldUpdateScrollFn } from './default_should_update_scroll';
+import { ScrollBehaviorContext } from './scroll_context';
+
+interface ScrollContainerProps {
+  /**
+   * This key must be static for the element & not change
+   * while the component is mounted.
+   */
+  scrollKey: string;
+  shouldUpdateScroll?: ShouldUpdateScrollFn;
+  children: React.ReactElement;
+}
+
+/**
+ * `ScrollContainer` is used to manage the scroll position of elements on the page
+ * that can be scrolled independently of the page body.
+ * This component is a port of the unmaintained https://github.com/ytase/react-router-scroll/
+ */
+
+export const ScrollContainer: React.FC<ScrollContainerProps> = ({
+  children,
+  scrollKey,
+  shouldUpdateScroll = defaultShouldUpdateScroll,
+}) => {
+  const scrollBehaviorContext = useContext(ScrollBehaviorContext);
+
+  const containerRef = useRef<HTMLElement>();
+
+  /**
+   * Register/unregister scrollable element with ScrollBehavior
+   */
+  useEffect(() => {
+    if (!scrollBehaviorContext || !containerRef.current) {
+      return;
+    }
+
+    scrollBehaviorContext.registerElement(
+      scrollKey,
+      containerRef.current,
+      (prevLocation, location) => {
+        // Hack to allow accessing scrollBehavior._stateStorage
+        return shouldUpdateScroll.call(
+          scrollBehaviorContext.scrollBehavior,
+          prevLocation,
+          location,
+        );
+      },
+    );
+
+    return () => {
+      scrollBehaviorContext.unregisterElement(scrollKey);
+    };
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, []);
+
+  return React.Children.only(
+    React.cloneElement(children, { ref: containerRef }),
+  );
+};

app/javascript/mastodon/containers/scroll_container/scroll_context.tsx

@@ -0,0 +1,141 @@
+import React, { useEffect, useMemo, useRef, useState } from 'react';
+
+import { useLocation, useHistory } from 'react-router-dom';
+
+import type { LocationBase } from 'scroll-behavior';
+import ScrollBehavior from 'scroll-behavior';
+
+import type {
+  LocationState,
+  MastodonLocation,
+} from 'mastodon/components/router';
+import { usePrevious } from 'mastodon/hooks/usePrevious';
+
+import { defaultShouldUpdateScroll } from './default_should_update_scroll';
+import type { ShouldUpdateScrollFn } from './default_should_update_scroll';
+import { SessionStorage } from './state_storage';
+
+type ScrollBehaviorInstance = InstanceType<
+  typeof ScrollBehavior<LocationBase, MastodonLocation>
+>;
+
+export interface ScrollBehaviorContextType {
+  registerElement: (
+    key: string,
+    element: HTMLElement,
+    shouldUpdateScroll: (
+      prevLocationContext: MastodonLocation | null,
+      locationContext: MastodonLocation,
+    ) => boolean,
+  ) => void;
+  unregisterElement: (key: string) => void;
+  scrollBehavior?: ScrollBehaviorInstance;
+}
+
+export const ScrollBehaviorContext =
+  React.createContext<ScrollBehaviorContextType | null>(null);
+
+interface ScrollContextProps {
+  shouldUpdateScroll?: ShouldUpdateScrollFn;
+  children: React.ReactElement;
+}
+
+/**
+ * A top-level wrapper that provides the app with an instance of the
+ * ScrollBehavior object. scroll-behavior is a library for managing the
+ * scroll position of a single-page app in the same way the browser would
+ * normally do for a multi-page app. This means it'll scroll back to top
+ * when navigating to a new page, and will restore the scroll position
+ * when navigating e.g. using `history.back`.
+ * The library keeps a record of scroll positions in session storage.
+ *
+ * This component is a port of the unmaintained https://github.com/ytase/react-router-scroll/
+ */
+
+export const ScrollContext: React.FC<ScrollContextProps> = ({
+  children,
+  shouldUpdateScroll = defaultShouldUpdateScroll,
+}) => {
+  const location = useLocation<LocationState>();
+  const history = useHistory<LocationState>();
+
+  /**
+   * Keep the current location in a mutable ref so that ScrollBehavior's
+   * `getCurrentLocation` can access it without having to recreate the
+   * whole ScrollBehavior object
+   */
+  const currentLocationRef = useRef(location);
+  useEffect(() => {
+    currentLocationRef.current = location;
+  }, [location]);
+
+  /**
+   * Initialise ScrollBehavior object once – using state rather
+   * than a ref to simplify the types and ensure it's defined immediately.
+   */
+  const [scrollBehavior] = useState(
+    (): ScrollBehaviorInstance =>
+      new ScrollBehavior({
+        addNavigationListener: history.listen.bind(history),
+        stateStorage: new SessionStorage(),
+        getCurrentLocation: () =>
+          currentLocationRef.current as unknown as LocationBase,
+        shouldUpdateScroll: (
+          prevLocationContext: MastodonLocation | null,
+          locationContext: MastodonLocation,
+        ) =>
+          // Hack to allow accessing scrollBehavior._stateStorage
+          shouldUpdateScroll.call(
+            scrollBehavior,
+            prevLocationContext,
+            locationContext,
+          ),
+      }),
+  );
+
+  /**
+   * Handle scroll update when location changes
+   */
+  const prevLocation = usePrevious(location) ?? null;
+  useEffect(() => {
+    scrollBehavior.updateScroll(prevLocation, location);
+  }, [location, prevLocation, scrollBehavior]);
+
+  /**
+   * Stop Scrollbehavior on unmount
+   */
+  useEffect(() => {
+    return () => {
+      scrollBehavior.stop();
+    };
+  }, [scrollBehavior]);
+
+  /**
+   * Provide the app with a way to register separately scrollable
+   * elements to also be tracked by ScrollBehavior. (By default
+   * ScrollBehavior only handles scrolling on the main document body.)
+   */
+  const contextValue = useMemo<ScrollBehaviorContextType>(
+    () => ({
+      registerElement: (key, element, shouldUpdateScroll) => {
+        scrollBehavior.registerElement(
+          key,
+          element,
+          shouldUpdateScroll,
+          location,
+        );
+      },
+      unregisterElement: (key) => {
+        scrollBehavior.unregisterElement(key);
+      },
+      scrollBehavior,
+    }),
+    [location, scrollBehavior],
+  );
+
+  return (
+    <ScrollBehaviorContext.Provider value={contextValue}>
+      {React.Children.only(children)}
+    </ScrollBehaviorContext.Provider>
+  );
+};

app/javascript/mastodon/containers/scroll_container/state_storage.ts

@@ -0,0 +1,46 @@
+import type { LocationBase, ScrollPosition } from 'scroll-behavior';
+
+const STATE_KEY_PREFIX = '@@scroll|';
+
+interface LocationBaseWithKey extends LocationBase {
+  key?: string;
+}
+
+/**
+ * This module is part of our port of https://github.com/ytase/react-router-scroll/
+ * and handles storing scroll positions in SessionStorage.
+ * Stored positions (`[x, y]`) are keyed by the location key and an optional
+ * `scrollKey` that's used for to track separately scrollable elements other
+ * than the document body.
+ */
+
+export class SessionStorage {
+  read(
+    location: LocationBaseWithKey,
+    key: string | null,
+  ): ScrollPosition | null {
+    const stateKey = this.getStateKey(location, key);
+
+    try {
+      const value = sessionStorage.getItem(stateKey);
+      return value ? (JSON.parse(value) as ScrollPosition) : null;
+    } catch {
+      return null;
+    }
+  }
+
+  save(location: LocationBaseWithKey, key: string | null, value: unknown) {
+    const stateKey = this.getStateKey(location, key);
+    const storedValue = JSON.stringify(value);
+
+    try {
+      sessionStorage.setItem(stateKey, storedValue);
+    } catch {}
+  }
+
+  getStateKey(location: LocationBaseWithKey, key: string | null) {
+    const locationKey = location.key;
+    const stateKeyBase = `${STATE_KEY_PREFIX}${locationKey}`;
+    return key == null ? stateKeyBase : `${stateKeyBase}|${key}`;
+  }
+}

app/javascript/mastodon/features/directory/index.tsx

@@ -21,7 +21,7 @@ import { ColumnHeader } from 'mastodon/components/column_header';
 import { LoadMore } from 'mastodon/components/load_more';
 import { LoadingIndicator } from 'mastodon/components/loading_indicator';
 import { RadioButton } from 'mastodon/components/radio_button';
-import ScrollContainer from 'mastodon/containers/scroll_container';
+import { ScrollContainer } from 'mastodon/containers/scroll_container';
 import { useSearchParam } from 'mastodon/hooks/useSearchParam';
 import { useAppDispatch, useAppSelector } from 'mastodon/store';
 
@@ -206,7 +206,6 @@ export const Directory: React.FC<{
       />
 
       {multiColumn && !pinned ? (
-        // @ts-expect-error ScrollContainer is not properly typed yet
         <ScrollContainer scrollKey='directory'>
           {scrollableArea}
         </ScrollContainer>

app/javascript/mastodon/features/status/index.jsx

@@ -16,7 +16,7 @@ import VisibilityOffIcon from '@/material-icons/400-24px/visibility_off.svg?reac
 import { Hotkeys }  from 'mastodon/components/hotkeys';
 import { Icon }  from 'mastodon/components/icon';
 import { LoadingIndicator } from 'mastodon/components/loading_indicator';
-import ScrollContainer from 'mastodon/containers/scroll_container';
+import { ScrollContainer } from 'mastodon/containers/scroll_container';
 import BundleColumnError from 'mastodon/features/ui/components/bundle_column_error';
 import { identityContextPropShape, withIdentity } from 'mastodon/identity_context';
 import { WithRouterPropTypes } from 'mastodon/utils/react_router';
@@ -526,9 +526,9 @@ class Status extends ImmutablePureComponent {
     this.setState({ fullscreen: isFullscreen() });
   };
 
-  shouldUpdateScroll = (prevRouterProps, { location }) => {
+  shouldUpdateScroll = (prevLocation, location) => {
     // Do not change scroll when opening a modal
-    if (location.state?.mastodonModalKey !== prevRouterProps?.location?.state?.mastodonModalKey) {
+    if (location.state?.mastodonModalKey !== prevLocation?.state?.mastodonModalKey) {
       return false;
     }