NextJS/Vercel not serving .pdf file in public folder in production

I have a PDF file in my public folder (next js app), which I'm attaching to an email (sendgrid).

In development, everything is working fine. Also when I run build + run start. So I suppose this has something to do with Vercel. When I check the logs in production (Vercel), I see following error:

> Error: ENOENT: no such file or directory, open 'public/assets/Bonus_1.pdf'

Any ideas on how to solve this problem?

Here's the relevant code:

const pathToAttachment1 = path.join("public", "assets", "Bonus_1.pdf")
const attachment1 = fs.readFileSync(pathToAttachment1).toString("base64");
    
sgMail.setApiKey(process.env.SENDGRID_API_KEY);
const msg = {
     to: process.env.NODE_ENV === "development" ? "info@test.com" : email,
     from: "test",
     attachments: [
            {
              content: attachment1,
              filename: "Bonus_1.pdf",
              type: "application/pdf",
              disposition: "attachment",
            },
          ],
          templateId: "xxx",
        };
sgMail.send(msg).then(() => {res.status(200).json({ message: "Mail sen!" });
});

To check the assets in the public directory I've added following code:

const files = fs.readdirSync(path.join("public", "assets"))
console.log("files:", files)

The output looks as follows:

files: [
  '1.png',
  'Bonus_1.pdf' ]

If the file is contained in the public directory, the path you have provided is wrong. The public folder does not to be included in the resource path.

Taking that into account your path should be: /assets/Bonus_1.pdf.

Remember

Vercel's deployment file system is read only, so any actions that will cause the file to be opened or modified like when using certain methods of the fs module, will error when deployed to the cloud.

I initially assumed that you are running your code under the app dir (and your code worked perfectly fine there in my tests), but I was finally able to replicate your issue under the pages/api.

path.resolve should resolve your error:

const file = fs
  .readFileSync(path.resolve("public/assets/Bonus_1.pdf"))
  .toString("base64");