How to fix EdgeFunctionError: Boot error in Supabase

First, verify your Edge Function code has no syntax errors. Use TypeScript compiler locally:

# Check TypeScript compilation
npx tsc --noEmit --target es2020 --module esnext your-function.ts

# Or use Deno directly to check
deno check your-function.ts

Common syntax issues to check:
1. Missing imports: Ensure all imported modules are available
2. Type errors: Fix TypeScript type mismatches
3. Async/await issues: Ensure proper async function structure
4. Export errors: Make sure handler function is properly exported

Example of correct function structure:

// Correct: Proper async handler with export
import { createClient } from 'https://esm.sh/@supabase/supabase-js@2'

const corsHeaders = {
  'Access-Control-Allow-Origin': '*',
  'Access-Control-Allow-Headers': 'authorization, x-client-info, apikey, content-type',
}

export async function handler(req: Request) {
  // Handle CORS preflight
  if (req.method === 'OPTIONS') {
    return new Response('ok', { headers: corsHeaders })
  }

  try {
    // Your function logic here
    const result = await processRequest(req);
    return new Response(JSON.stringify(result), {
      status: 200,
      headers: { ...corsHeaders, 'Content-Type': 'application/json' }
    });
  } catch (error) {
    console.error('Error:', error);
    return new Response(JSON.stringify({ error: error.message }), {
      status: 500,
      headers: { ...corsHeaders, 'Content-Type': 'application/json' }
    });
  }
}

Check that all imported modules are available and compatible with Deno:

// Common import issues and fixes:

// 1. Check import URLs - use esm.sh for npm packages
// BAD: import { something } from 'some-package'; // Won't work in Deno
// GOOD: import { something } from 'https://esm.sh/some-package';

// 2. Verify version compatibility
import { createClient } from 'https://esm.sh/@supabase/supabase-js@2'; // Specify version

// 3. Check for circular dependencies
// If file A imports B, and B imports A, you'll get boot errors

// 4. Test imports locally
deno cache --reload https://esm.sh/@supabase/supabase-js@2

To diagnose import issues:
1. Check Deno cache: deno cache your-function.ts
2. Look for 404 errors: Missing modules will show as network errors
3. Verify CDN availability: esm.sh or other CDNs might be temporarily unavailable
4. Check version constraints: Some packages may not be compatible with Deno

If using private dependencies, ensure they're properly configured in your Supabase project.

Ensure all required environment variables are set and accessible:

# Check current environment variables in Supabase Dashboard
# Go to: Project Settings → API → Config

# Verify in your function code
console.log('Environment check:', {
  hasSupabaseUrl: !!Deno.env.get('SUPABASE_URL'),
  hasSupabaseKey: !!Deno.env.get('SUPABASE_ANON_KEY'),
  // Add other required variables
});

Common environment issues:
1. Missing variables: Required env vars not set in Supabase Dashboard
2. Incorrect names: Variable names don't match what code expects
3. Permission issues: Function doesn't have access to certain variables
4. Type mismatches: Code expects string but gets number/boolean

To fix:
1. Set variables in Supabase Dashboard:
- Go to Project → Edge Functions → Select function → Settings
- Add required environment variables

2. Use fallback values in code:

const supabaseUrl = Deno.env.get('SUPABASE_URL') || 'https://default.example.com';
const supabaseKey = Deno.env.get('SUPABASE_ANON_KEY') || 'default-key';

if (!supabaseUrl || !supabaseKey) {
  throw new Error('Missing Supabase configuration');
}

3. Test locally with .env file:

# Create .env file
SUPABASE_URL=https://your-project.supabase.co
SUPABASE_ANON_KEY=your-anon-key

# Run function with env vars
supabase functions serve --env-file .env

Use Supabase CLI to test functions locally before deployment:

# Install Supabase CLI if not already installed
# Follow: https://supabase.com/docs/guides/cli

# Start local development
supabase start

# Serve functions locally
supabase functions serve your-function

# Test the function
curl -X POST http://localhost:54321/functions/v1/your-function   -H "Authorization: Bearer $ANON_KEY"   -H "Content-Type: application/json"   -d '{"test": "data"}'

Local testing helps identify:
1. Boot errors before they reach production
2. Environment issues in local setup
3. Dependency problems during local execution
4. Network/connectivity issues

If local testing works but deployment fails:
1. Check Supabase project compatibility: Ensure local and remote versions match
2. Verify deployment command: supabase functions deploy your-function --project-ref your-project-ref
3. Check logs: Use supabase functions logs your-function to see deployment errors
4. Try incremental deployment: Deploy with --no-verify-jwt flag to isolate JWT issues

Ensure your code is compatible with the Deno runtime version used by Supabase:

// Check Deno version and features
console.log('Deno version:', Deno.version);
console.log('Deno features:', {
  hasWebSocket: 'WebSocket' in globalThis,
  hasCrypto: 'crypto' in globalThis,
  hasFetch: 'fetch' in globalThis,
});

// Test Deno-specific APIs
try {
  await Deno.readTextFile('./test.txt');
  console.log('File API available');
} catch (error) {
  console.log('File API error:', error.message);
}

Common Deno compatibility issues:
1. Node.js APIs: Don't use Node.js-specific APIs (require, __dirname, etc.)
2. Global variables: Some browser globals may not be available
3. Permission model: Deno requires explicit permissions (network, env, read, etc.)
4. Module system: Uses ES modules, not CommonJS

Solutions:
1. Use Deno-compatible libraries: Check https://deno.land/x/ for Deno-native packages
2. Polyfill missing APIs: Use compatibility layers if needed
3. Check Supabase documentation: For supported Deno versions and features
4. Simplify code: Remove complex dependencies that may cause compatibility issues

Examine detailed logs to identify the specific boot error cause:

# Get deployment logs
supabase functions logs your-function-name --follow

# Filter for boot/initialization errors
supabase functions logs your-function-name | grep -i "boot|init|error"

# Check Supabase Dashboard logs
# Go to: Edge Functions → Select function → Logs

Common log patterns and fixes:
1. "Module not found": Add missing import or fix import URL
2. "Permission denied": Check file permissions and Deno permissions
3. "SyntaxError": Fix JavaScript/TypeScript syntax
4. "Memory limit exceeded": Reduce initialization memory usage
5. "Network error": Check internet connectivity during deployment

For persistent issues:
1. Create minimal reproduction: Strip function down to bare essentials
2. Deploy empty function: Test with just export async function handler() { return new Response("OK") }
3. Check Supabase status: Visit https://status.supabase.com for service issues
4. Contact support: Use Supabase Discord or GitHub discussions for help