Add type support to react useAgent().call

[ruifigueira]

Proposal to add type support to react useAgent() RPC calls. It can infer argument tyoes and ensure we pass all required values.

Usage example:

// server.ts
class MyAgent extends Agent<typeof env, {}> {
  @callable()
  sayHello(name?: string): string {
    return `Hello, ${name ?? 'World'}!`;
  }
  
  @callable()
  async perform(task: string, p1?: number): Promise<void> {
    // do something
  }

  // not annotated with @callable()
  nonRpc(): void {
  }
}

// index.tsx
import type { MyAgent } from './server.ts';

// ...

const agent = useAgent<{}, MyAgent>({ agent: 'my-agent' });
// return type is promisified
agent.call('sayHello') satisfies Promise<string>;

// @ts-expect-error first argument is not a string
await agent.call('sayHello', [1]);

await agent.call('perform', ['some task', 1]);
await agent.call('perform', ['another task']);
// @ts-expect-error requires parameters
await agent.call('perform');

// we cannot exclude it because typescript doesn't have a way
// to exclude based on decorators
await agent.call('nonRpc');

Intellisense in vscode:

Unfortunately, I didn't find a way to restrict calls to methods decorated with @callable(), so it will also suggest non-RPC methods.
Nevertheless, I excluded the ones declared in the base Agent class to ensure intellisense is as clean as possible.

If there are public methods to exclude, it's always possible to exclude the non-RPC ones with Omit<MyAgent, 'noRpc'>:

[changeset-bot]

🦋 Changeset detected

Latest commit: ac80e64

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
agents	Patch
hono-agents	Patch

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Click here if you're a maintainer who wants to add another changeset to this PR

[threepointone]

this is great, thanks so much! a couple of questions

[threepointone]

I fixed some lint checks, and rebased on top of previous changes. There are a bunch of explicit anys, which I try to keep out of the codebase. If possible, could you replace them? If not possible, it's fine to skip the check with a //biome-ignore statement

You can run npm run check at the root to see whether it would pass checks btw

[ruifigueira]

I had to ignore those errors for now. Maybe in the future we can improve type checking for RPC and restrict types to the ones that are JSON compatible.

[threepointone]

there's still a type failure in rpc.tsx, which shows that it fails if you don't have an explicit type param passed, can we make it so that's still acceptable? a default <Agent, State> value?

[ruifigueira]

It seems that switching the order of overload functions fixes it.

[threepointone]

This is awesome, thanks for iterating on it. I'll do one final review and test it out tomorrow and land it. Great PR!