Managing Local File Access for Next.js 14.1 Server Actions on Vercel

Fixing File Access Problems in Next.js 14.1 Server Actions Using Various Methods

To securely access local files in production, this solution makes use of a Node.js backend with an API route.

const { PDFDocument } = require('pdf-lib');
const fs = require('fs');
const path = require('path');
export default async function handler(req, res) {
  try {
    const pdfDataDir = path.join(process.cwd(), 'actions', 'pdf_data');
    const templatePath = path.join(pdfDataDir, 'template.pdf');
    const pdfDoc = await PDFDocument.load(fs.readFileSync(templatePath));
    const pdfBytes = await pdfDoc.save();
    res.setHeader('Content-Type', 'application/pdf');
    res.status(200).send(pdfBytes);
  } catch (error) {
    res.status(500).send('Error generating PDF');
  }
}

Next, use the Modular Webpack Configuration to copy files.Production Builds for JavaScript

In order to guarantee that local files are properly bundled in production, this approach alters the Webpack settings.

const CopyPlugin = require('copy-webpack-plugin');
const path = require('path');
module.exports = {
  webpack: (config, { dev, isServer }) => {
    if (!dev && isServer) {
      config.plugins.push(
        new CopyPlugin({
          patterns: [{
            from: path.join(__dirname, 'actions', 'pdf_data'),
            to: path.join(__dirname, '.next', 'server', 'actions', 'pdf_data'),
          }],
        })
      );
    }
    return config;
  },
};

Accessing Files Dynamically Using API Routes Instead of Server Actions

With this method, we use API routes instead of dynamic file access to provide production-ready local file serving.

import { promises as fs } from 'fs';
import path from 'path';
export default async function handler(req, res) {
  try {
    const pdfDataDir = path.join(process.cwd(), 'actions', 'pdf_data');
    const filePath = path.join(pdfDataDir, 'template.pdf');
    const file = await fs.readFile(filePath);
    res.setHeader('Content-Type', 'application/pdf');
    res.status(200).send(file);
  } catch (err) {
    res.status(500).send('Error loading file');
  }
}

Unit Test for File Access in API Route

This unit test confirms that a PDF file is appropriately served by the API route.

import handler from '../pages/api/generate-pdf';
import { createMocks } from 'node-mocks-http';
describe('PDF Generation API', () => {
  it('should return a PDF', async () => {
    const { req, res } = createMocks({ method: 'GET' });
    await handler(req, res);
    expect(res._getStatusCode()).toBe(200);
    expect(res._getHeaders()['content-type']).toBe('application/pdf');
  });
});

Common Questions on Handling Local Files in Next.js Server Actions

1. How can I ensure local files are available in production?
2. By include CopyPlugin in your Webpack configuration, you can ensure that local assets, such as PDFs and fonts, are bundled into the build and made accessible.
3. Why do I get ENOENT errors in production?
4. The reason for this error is that in systems such as Vercel, the files or directories you are attempting to access were not included in the production build.
5. I want to access files, however can I utilize API routes instead of server actions?
6. Yes, you may have additional control and guarantee that files are provided correctly in a production environment by transferring the file access functionality to an API route.
7. What is the role of process.cwd() in file paths?
8. process.cwd() provides the current working directory, assisting in the dynamic creation of file paths independent of environment variations.
9. Should I use @vercel/blob for file storage?
10. Although @vercel/blob is an option, it can cause processes like PDF production to lag. Faster options can be API routes or direct file access.

Final Thoughts on Handling Local File Access

Accessing local files can be a big difficulty when using server actions in Next.js 14.1, particularly on Vercel. However, developers may make sure their files are packed and available in production by using technologies like Webpack's CopyPlugin and API routes.

You can steer clear of any problems by concentrating on dynamic file handling techniques, like shifting file functionality to API routes. Further research into file access techniques may result in even more effective solutions for later deployments.