fix: PDF export broken in Docker and Serverless (Vercel) environments

[ramanujamgond]

Summary

Fixes #885 - PDF export broken on dillinger.io

This PR fixes the PDF export functionality that fails in both Docker and serverless (Vercel/AWS Lambda) environments.

Issues Addressed

Docker Environment Error

Failed to move to new namespace: PID namespaces supported, Network namespace supported, 
but failed: errno = Operation not permitted

Serverless (Vercel) Environment Error

Could not find Chrome (ver. 142.0.7444.175). This can occur if either
1. you did not perform an installation before running the script
2. your cache path is incorrectly configured (which is: /home/sbx_user1051/.cache/puppeteer)

Root Cause Analysis

1. Incorrect launch_options Format

The md-to-pdf library expects launch_options to be an object matching Puppeteer's launch options format, but it was incorrectly passed as an array.

2. Docker Security Restrictions

Docker's default seccomp profile blocks the system calls that Chromium needs to create namespaces for its sandbox.

3. Serverless Chrome Missing

Serverless platforms like Vercel don't have Chrome pre-installed. The standard Puppeteer package tries to find Chrome in a cache directory that doesn't exist in these environments.

Changes Made

plugins/core/server.js

• Added smart environment detection using @sparticuz/chromium
• Serverless mode: Uses @sparticuz/chromium for Vercel/Lambda environments
• Docker mode: Falls back to system Chrome with proper sandbox flags

let chromium
try {
  chromium = require('@sparticuz/chromium')
} catch (e) {
  chromium = null
}

// In markdown2Pdf:
if (chromium) {
  // Serverless (Vercel, AWS Lambda)
  launchOptions = {
    args: chromium.args,
    executablePath: await chromium.executablePath(),
    headless: chromium.headless
  }
} else {
  // Docker/traditional server
  launchOptions = {
    executablePath: process.env.PUPPETEER_EXECUTABLE_PATH || undefined,
    args: ['--no-sandbox', '--disable-setuid-sandbox', '--disable-dev-shm-usage', 
           '--disable-gpu', '--single-process', '--no-zygote']
  }
}

package.json

• Added @sparticuz/chromium: ^131.0.0 dependency for serverless Chrome support

docker-compose.yml

• Added security_opt: seccomp=unconfined - Disables seccomp filtering
• Added cap_add: SYS_ADMIN - Grants capability for namespace operations

Validation

This fix has been validated against multiple sources:

• Puppeteer Troubleshooting Guide
• @sparticuz/chromium documentation
• Vercel Puppeteer examples
• Stack Overflow: Puppeteer Docker namespace issues
• dev.to: Puppeteer on Vercel

Testing

Docker

docker-compose down
docker-compose build --no-cache
docker-compose up

Vercel

The @sparticuz/chromium package is automatically detected and used when deployed to Vercel.

Note for Maintainers

If Vercel deployment still has issues, you may need to:

1. Ensure the Vercel function has sufficient memory (1024MB+ recommended)
2. Check if libnss3.so or other dependencies are missing (may require custom build)

[vercel]

@ramanujamgond is attempting to deploy a commit to the Joe McCann's projects Team on Vercel.

A member of the Team first needs to authorize it.