Implement automatic self-referential bindings via ctx.exports.

[kentonv]

For every top-level export, ctx.exports will contain a corresponding property which acts as a binding to that export. If the export is a simple object or WorkerEntrypoint, then the ctx.exports property is a service binding. If the export is a Durable Object class (and it has been configured with storage), the ctx.exports property is a DO namespace binding.

So you can do: ctx.exports.MyEntrypoint.someRpc()

And it calls someRpc() on the entrypoint named MyEntrypoint, as if you had called it over a service binding.

This is marked experimental for now since it won't work on the edge until further changes are made to our control plane.

[kentonv]

cc @geelen @irvinebroque

[github-actions]

The generated output of @cloudflare/workers-types has been changed by this PR. If this is intentional, run bazel build //types && rm -rf types/generated-snapshot && cp -r bazel-bin/types/definitions types/generated-snapshot to update the snapshot. Alternatively, you can download the full generated types: https://github.com/cloudflare/workerd/actions/runs/13209840682/artifacts/2557262691

Full Type Diff

diff -r bazel-bin/types/definitions/experimental/index.d.ts types/generated-snapshot/experimental/index.d.ts
568d567
<   exports: any;
diff -r bazel-bin/types/definitions/experimental/index.ts types/generated-snapshot/experimental/index.ts
573d572
<   exports: any;

[geelen]

I think we need to extend the typedefs for WorkerEntrypoint and DurableObject and ExecutionContext:

type ExportBindings<T> = {
  [K in keyof T]: T[K] extends typeof DurableObject 
    ? DurableObjectNamespace<InstanceType<T[K]>>
    : T[K] extends typeof WorkerEntrypoint
      ? Service<InstanceType<T[K]>>
      : never;
  }

  export abstract class WorkerEntrypoint<Env = unknown, Exports extends Record<string, unknown>>
    implements Rpc.WorkerEntrypointBranded
  {
    [Rpc.__WORKER_ENTRYPOINT_BRAND]: never;
    protected ctx: ExecutionContext<ExportBindings<Exports>>;
    // ...

'tested' here

Similar change required for DurableObject base class

Usage:

import { WorkerEntrypoint, DurableObject } from "cloudflare:workers";

// These can be autogenerated by `wrangler types`
type Env = {}
type Exports = { MyEntrypoint, AnotherEntrypoint, MyActor, UnconfiguredActor }

export default {
  async fetch(request: Request, env: Env, ctx: ExecutionContext<Exports>) {
    // ...
  }
}
export class MyEntrypoint extends WorkerEntrypoint<Env, Exports> {
  foo(i) { return `foo: ${i}` }
}
export class AnotherEntrypoint extends WorkerEntrypoint<Env, Exports> {
  bar(i) { return `bar: ${i}` }
}
export class MyActor extends DurableObject<Env, Exports> {
  setValue(i) { this.value = i; }
  baz() { return `baz: ${this.value}` }
}
export class UnconfiguredActor extends DurableObject<Env, Exports> {
  qux(i) { return `qux: ${i}` }
}

Can bump this to a second PR when we make this non-experimental, if you like? I just wanted to jot down the definition of ExportBindings<Exports> while I thought of it

---

Edit: I just realised we're going to need a type param for ctx.props too, in all three places. Would be nice to have a single argument so you can leave any of them unspecified like Hono: WorkerEntrypoint<{ Env, Exports, Props }>. I wonder how if we can do that without a breaking change :grimace:

[kentonv]

@jasnell Sorry to always assign you on everything but when I looked at the history of the files I'm modifying it's basically all me and you!

[kentonv]

(Added a test for ctx.exports.default.)

[kentonv]

(Added commit to add ctx.exports to Durable Objects' ctx as well.)