custom-binding

Custom env binding: env.EMAIL

Demonstrates how a Go embedder adds a binding that Ramune itself does not ship. The same pattern works for queues, object stores, caches, AI providers — any env.FOO you want.

Run

go run .
# in another terminal:
curl -X POST http://localhost:3333/notify \
    -H "Content-Type: application/json" \
    -d '{"user":"alice@example.com","body":"welcome"}'

The Go server prints each EMAIL.send call on stdout:

[EMAIL] to=alice@example.com subject="Hello from Ramune" body="welcome"

What to look at

• main.go — the Go embedder.
  • installEmailBinding registers __env_email_send via rt.RegisterFunc. That's the actual Go → JS bridge.
  • emailFacadeJS is passed to workers.WithExtraEnvJS; it attaches env.EMAIL = { send(opts) { ... } } via the globalThis.__extraEnvBindings(env) composition hook.
  • workers.Register wires the worker up; no Ramune changes needed.
• worker.ts — the Workers-style handler uses env.EMAIL.send(...) exactly like it would use env.KV.get(...).
• workers-env.d.ts — declares the Env.EMAIL type so the editor and ramune check see the binding.

Reuse as a Go package

The installEmailBinding + emailFacadeJS pair is everything a reusable ramune-<x> package needs to expose. Keep the IIFE composition around prev in emailFacadeJS so callers can stack bindings from multiple packages without collisions:

mailbinding.Install(rt, smtp)
queuebinding.Install(rt, nats)
blobbinding.Install(rt, s3)

extraJS := mailbinding.FacadeJS + queuebinding.FacadeJS + blobbinding.FacadeJS
workers.Register(rt, ..., workers.WithExtraEnvJS(extraJS))

See workers/BINDINGS.md for the full guide.