import/export: Make sure Express sees async errors

Express v4.x does not check to see if a Promise returned from a
middleware function will be rejected, so explicitly pass the Promise
rejection reason to `next()`.

We can revert this change after we upgrade to Express v5.0.

See https://expressjs.com/en/guide/error-handling.html for details.

src/node/hooks/express/importexport.js

@@ -21,7 +21,8 @@ const limiter = rateLimit(settings.importExportRateLimiting);
 exports.expressCreateServer = (hookName, args, cb) => {
   // handle export requests
   args.app.use('/p/:pad/:rev?/export/:type', limiter);
-  args.app.get('/p/:pad/:rev?/export/:type', async (req, res, next) => {
+  args.app.get('/p/:pad/:rev?/export/:type', (req, res, next) => {
+    (async () => {
       const types = ['pdf', 'doc', 'txt', 'html', 'odt', 'etherpad'];
       // send a 404 if we don't support this filetype
       if (types.indexOf(req.params.type) === -1) {
@@ -61,11 +62,13 @@ exports.expressCreateServer = (hookName, args, cb) => {
         console.log(`Exporting pad "${req.params.pad}" in ${req.params.type} format`);
         exportHandler.doExport(req, res, padId, readOnlyId, req.params.type);
       }
+    })().catch((err) => next(err || new Error(err)));
   });
 
   // handle import requests
   args.app.use('/p/:pad/import', limiter);
-  args.app.post('/p/:pad/import', async (req, res, next) => {
+  args.app.post('/p/:pad/import', (req, res, next) => {
+    (async () => {
       const {session: {user} = {}} = req;
       const {accessStatus} = await securityManager.checkAccess(
           req.params.pad, req.cookies.sessionID, req.cookies.token, user);
@@ -73,6 +76,7 @@ exports.expressCreateServer = (hookName, args, cb) => {
         return res.status(403).send('Forbidden');
       }
       await importHandler.doImport(req, res, req.params.pad);
+    })().catch((err) => next(err || new Error(err)));
   });
 
   return cb();