My Node.js application has a feature that allows users to upload files, and the permissions are enforced using Express middleware with the help of multer.
The usual route first authenticates the user, checks if they have the necessary permission, and then processes the file import. Here's an example:
router.post('/:id/import', passport.authenticate('jwt', { session: false }), permit('admin'), function(req, res, next) {
MyClass.doImport(req.file.path).then(function(result) {
res.json(result);
}).catch(function(error) {
res.status(500).json(error);
});
});
Everything works smoothly when there are no errors, and the imported file gets deleted afterwards. However, in case of any errors (such as unauthorized access), the uploaded file remains on the disk.
I want to prevent the creation of any file on disk until all the permission checks by middleware are successfully completed. I've attempted placing multer at the end of the middleware chain like this:
var app = express();
app.use( // ...
app.use(passport.initialize());
app.use(multer({dest:'./tmp/'}).single('file'));
However, even on an authentication error, a file still gets created in the 'tmp' directory.
Is there a way to delay the file creation until all other middleware processes have finished successfully?
If not feasible, can I introduce a new middleware function that runs only if there is a file attachment and an error occurs further up the chain?