fix(materials): display custom error page when file is missing in cou…

…rse materials

client/app/bundles/course/material/folderLoader.ts

@@ -0,0 +1,15 @@
+import { LoaderFunction, redirect } from 'react-router-dom';
+import { getIdFromUnknown } from 'utilities';
+
+import CourseAPI from 'api/course';
+
+const folderLoader: LoaderFunction = async ({ params }) => {
+  const folderId = getIdFromUnknown(params?.folderId);
+  if (!folderId) return redirect('/');
+
+  const { data } = await CourseAPI.folders.fetch(folderId);
+
+  return data;
+};
+
+export default folderLoader;

client/app/bundles/course/material/folders/handles.ts

@@ -7,17 +7,26 @@ const getFolderTitle = async (
   courseUrl: string,
   folderId: number,
 ): Promise<CrumbPath> => {
-  const { data } = await CourseAPI.folders.fetch(folderId);
+  try {
+    const { data } = await CourseAPI.folders.fetch(folderId);
+    const workbinUrl = `${courseUrl}/materials/folders/${data.breadcrumbs[0].id}`;
 
-  const workbinUrl = `${courseUrl}/materials/folders/${data.breadcrumbs[0].id}`;
-
-  return {
-    activePath: workbinUrl,
-    content: data.breadcrumbs.map((crumb) => ({
-      title: crumb.name,
-      url: `materials/folders/${crumb.id}`,
-    })),
-  };
+    return {
+      activePath: workbinUrl,
+      content: data.breadcrumbs.map((crumb) => ({
+        title: crumb.name,
+        url: `materials/folders/${crumb.id}`,
+      })),
+    };
+  } catch (error) {
+    return {
+      activePath: courseUrl,
+      content: {
+        title: 'Folder Not Found',
+        url: courseUrl,
+      },
+    };
+  }
 };
 
 /**

client/app/bundles/course/material/folders/pages/BaseRetrievePage.tsx

@@ -0,0 +1,35 @@
+import { ReactNode } from 'react';
+import { Typography } from '@mui/material';
+
+import Page from 'lib/components/core/layouts/Page';
+
+interface BaseRetrievePageProps {
+  illustration: ReactNode;
+  title: string;
+  description: string;
+  children?: ReactNode;
+}
+
+const BaseRetrievePage = (
+  props: BaseRetrievePageProps,
+): JSX.Element => (
+  <Page className="h-full m-auto flex flex-col items-center justify-center text-center">
+    {props.illustration}
+
+    <Typography className="mt-5" variant="h6">
+      {props.title}
+    </Typography>
+
+    <Typography
+      className="max-w-3xl mt-2"
+      color="text.secondary"
+      variant="body2"
+    >
+      {props.description}
+    </Typography>
+
+    {props.children}
+  </Page>
+);
+
+export default BaseRetrievePage;

client/app/bundles/course/material/folders/pages/ErrorRetrievingFolderPage.tsx

@@ -0,0 +1,55 @@
+import React from 'react';
+import { defineMessages } from 'react-intl';
+import { useParams } from 'react-router-dom';
+import { Cancel, InsertDriveFileOutlined } from '@mui/icons-material';
+
+import Link from 'lib/components/core/Link';
+import useTranslation from 'lib/hooks/useTranslation';
+
+import BaseRetrievePage from './BaseRetrievePage';
+
+const translations = defineMessages({
+  problemRetrievingFolder: {
+    id: 'course.material.folders.ErrorRetrievingFolderPage.problemRetrievingFolder',
+    defaultMessage: 'Problem retrieving folder',
+  },
+  problemRetrievingFolderDescription: {
+    id: 'course.material.folders.ErrorRetrievingFolderPage.problemRetrievingFolderDescription',
+    defaultMessage:
+      "Either it no longer exists, you don't have the permission to access it, or something unexpected happened when we were trying to retrieve it.",
+  },
+  goToTheWorkbin: {
+    id: 'course.material.folders.ErrorRetrievingFolderPage.goToTheWorkbin',
+    defaultMessage: 'Go to the Workbin',
+  },
+});
+
+const ErrorRetrievingFolderPage = (): JSX.Element => {
+  const { t } = useTranslation();
+
+  const params = useParams();
+  const workbinURL = `/courses/${params.courseId}`;
+
+  return (
+    <BaseRetrievePage
+      description={t(translations.problemRetrievingFolderDescription)}
+      illustration={
+        <div className="relative">
+          <InsertDriveFileOutlined className="text-[6rem]" color="disabled" />
+
+          <Cancel
+            className="absolute bottom-0 -right-2 text-[4rem] bg-white rounded-full"
+            color="error"
+          />
+        </div>
+      }
+      title={t(translations.problemRetrievingFolder)}
+    >
+      <Link className="mt-10" to={workbinURL}>
+        {t(translations.goToTheWorkbin)}
+      </Link>
+    </BaseRetrievePage>
+  );
+};
+
+export default ErrorRetrievingFolderPage;

client/app/bundles/course/material/folders/pages/FolderShow/index.tsx

@@ -1,6 +1,6 @@
 import { FC, ReactElement, useEffect, useState } from 'react';
 import { defineMessages } from 'react-intl';
-import { useParams } from 'react-router-dom';
+import {useLoaderData, useParams} from 'react-router-dom';
 
 import EditButton from 'lib/components/core/buttons/EditButton';
 import Page from 'lib/components/core/layouts/Page';
@@ -37,6 +37,8 @@ const FolderShow: FC = () => {
   const { t } = useTranslation();
   const dispatch = useAppDispatch();
 
+  const data = useLoaderData();
+  if (!data) throw new Error('No download data. This should never happen.');
   // For new folder form dialog
   const [isNewFolderOpen, setIsNewFolderOpen] = useState(false);
   // For edit folder form dialog

client/app/routers/AuthenticatedApp.tsx

@@ -67,6 +67,7 @@ import LessonPlanShow from 'bundles/course/lesson-plan/pages/LessonPlanShow';
 import LevelsIndex from 'bundles/course/level/pages/LevelsIndex';
 import DownloadingFilePage from 'bundles/course/material/files/DownloadingFilePage';
 import ErrorRetrievingFilePage from 'bundles/course/material/files/ErrorRetrievingFilePage';
+import ErrorRetrievingFolderPage from 'bundles/course/material/folders/pages/ErrorRetrievingFolderPage';
 import FolderShow from 'bundles/course/material/folders/pages/FolderShow';
 import TimelineDesigner from 'bundles/course/reference-timelines/TimelineDesigner';
 import ResponseEdit from 'bundles/course/survey/pages/ResponseEdit';
@@ -127,6 +128,7 @@ import {
   forumTopicHandle,
 } from 'course/forum/handles';
 import { leaderboardHandle } from 'course/leaderboard/handles';
+import folderLoader from 'course/material/folderLoader';
 import { folderHandle } from 'course/material/folders/handles';
 import materialLoader from 'course/material/materialLoader';
 import { videoWatchHistoryHandle } from 'course/statistics/handles';
@@ -221,7 +223,9 @@ const authenticatedRouter: Translated<RouteObject[]> = (t) =>
               children: [
                 {
                   index: true,
+                  loader: folderLoader,
                   element: <FolderShow />,
+                  errorElement: <ErrorRetrievingFolderPage />,
                 },
                 {
                   path: 'files/:materialId',