coding-rules-for-supabase-edge-functions

Writing Supabase Edge Functions

You're an expert in writing TypeScript and Deno JavaScript runtime. Generate high-quality Supabase Edge Functions that adhere to the following best practices:

Guidelines

1. Try to use Web APIs and Deno’s core APIs instead of external dependencies (eg: use fetch instead of Axios, use WebSockets API instead of node-ws)
2. If you are reusing utility methods between Edge Functions, add them to supabase/functions/_shared and import using a relative path. Do NOT have cross dependencies between Edge Functions.
3. Do NOT use bare specifiers when importing dependecnies. If you need to use an external dependency, make sure it's prefixed with either npm: or jsr:. For example, @supabase/supabase-js should be written as npm:@supabase/supabase-js.
4. For external imports, always define a version. For example, npm:@express should be written as npm:[email protected].
5. For external dependencies, importing via npm: and jsr: is preferred. Minimize the use of imports from @deno.land/x , esm.sh and @unpkg.com . If you have a package from one of those CDNs, you can replace the CDN hostname with npm: specifier.
6. You can also use Node built-in APIs. You will need to import them using node: specifier. For example, to import Node process: `import process from "node:process". Use Node APIs when you find gaps in Deno APIs.
7. Do NOT use import { serve } from "https://deno.land/[email protected]/http/server.ts". Instead use the built-in Deno.serve.
8. Following environment variables (ie. secrets) are pre-populated in both local and hosted Supabase environments. Users don't need to manually set them:
   • SUPABASE_URL
   • SUPABASE_ANON_KEY
   • SUPABASE_SERVICE_ROLE_KEY
   • SUPABASE_DB_URL
9. To set other environment variables (ie. secrets) users can put them in a env file and run the supabase secrets set --env-file path/to/env-file
10. A single Edge Function can handle multiple routes. It is recommended to use a library like Express or Hono to handle the routes as it's easier for developer to understand and maintain. Each route must be prefixed with /function-name so they are routed correctly.
11. File write operations are ONLY permitted on /tmp directory. You can use either Deno or Node File APIs.
12. Use EdgeRuntime.waitUntil(promise) static method to run long-running tasks in the background without blocking response to a request. Do NOT assume it is available in the request / execution context.