feat: support notifications

src/client.ts

@@ -30,7 +30,7 @@ export class RpcError extends Error {
 export type RpcTransport = (
   req: JsonRpcRequest,
   abortSignal: AbortSignal
-) => Promise<JsonRpcResponse>;
+) => Promise<JsonRpcResponse | void>;
 
 type RpcClientOptions =
   | string
@@ -78,7 +78,7 @@ export function rpcClient<T extends object>(options: RpcClientOptions) {
     args: any[],
     signal: AbortSignal
   ) => {
-    const req = createRequest(method, args);
+    const req = createRequest(Date.now(), method, args);
     const raw = await transport(serialize(req as any), signal);
     const res = deserialize(raw);
     if ("result" in res) {
@@ -90,6 +90,20 @@ export function rpcClient<T extends object>(options: RpcClientOptions) {
     throw new TypeError("Invalid response");
   };
 
+  async function sendNotification(method: string, ...args: any[]): Promise<Promise<void>> {
+    const req = createRequest(undefined, method, args);
+    const ac = new AbortController();
+    const promise = transport(serialize(req as any), ac.signal);
+    abortControllers.set(promise, ac);
+    promise
+      .finally(() => {
+        // Remove the
+        abortControllers.delete(promise);
+      })
+      .catch(() => {});
+    return promise as Promise<void>;
+  }
+
   // Map of AbortControllers to abort pending requests
   const abortControllers = new WeakMap<Promise<any>, AbortController>();
 
@@ -101,6 +115,7 @@ export function rpcClient<T extends object>(options: RpcClientOptions) {
       const ac = abortControllers.get(promise);
       ac?.abort();
     },
+    $notify: sendNotification,
   };
 
   return new Proxy(target, {
@@ -130,13 +145,16 @@ export function rpcClient<T extends object>(options: RpcClientOptions) {
 /**
  * Create a JsonRpcRequest for the given method.
  */
-export function createRequest(method: string, params?: any[]): JsonRpcRequest {
+function createRequest(id: JsonRpcRequest['id'], method: string, params?: any[]): JsonRpcRequest {
   const req: JsonRpcRequest = {
     jsonrpc: "2.0",
-    id: Date.now(),
     method,
   };
 
+  if (id) {
+    req.id = id;
+  }
+
   if (params?.length) {
     req.params = removeTrailingUndefs(params);
   }

src/test/client.ts

@@ -116,3 +116,28 @@ tap.test("should not relay internal methods", async (t) => {
   //@ts-expect-error
   client[Symbol()];
 });
+
+tap.test("should not notify", async (t) => {
+  let client: ReturnType<typeof rpcClient<Service>>;
+
+  const request = new Promise((resolve) => {
+    client = rpcClient<Service>({
+      url: 'n/a',
+      transport: async (req) => {
+        resolve(req);
+      },
+    });
+  });
+
+  const res = await Promise.all([
+    client!.$notify("hello", "world"),
+    request,
+  ]);
+  t.equal(res[0], undefined);
+  t.same(res[1], {
+    "jsonrpc": "2.0",
+    "method": "hello",
+    "params": ["world"],
+    // no id
+  });
+});