feat: JSON-RPC responses async iterable iterator

wasm-node/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+### Added
+
+- Add `jsonRpcResponses` async iterable iterator to `Chain`, as a more convenient alternative to the `nextJsonRpcResponse` function. ([#1937](https://github.com/smol-dot/smoldot/pull/1937))
+
 ### Fixed
 
 - Fix potential panic in parachain syncing code. ([#1912](https://github.com/smol-dot/smoldot/pull/1912))

wasm-node/javascript/demo/demo-deno.ts

@@ -69,8 +69,7 @@ while(true) {
 
     (async () => {
         try {
-            while(true) {
-                const response = await chain.nextJsonRpcResponse();
+            for await (const response of chain.jsonRpcResponses) {
                 socket.send(response);
             }
         } catch(_error) {}

wasm-node/javascript/demo/demo.mjs

@@ -162,8 +162,7 @@ wsServer.on('connection', function (connection, request) {
 
             (async () => {
                 try {
-                    while(true) {
-                        const response = await para.nextJsonRpcResponse();
+                    for await (const response of para.jsonRpcResponses) {
                         connection.send(response);
                     }
                 } catch(_error) {}
@@ -177,8 +176,7 @@ wsServer.on('connection', function (connection, request) {
 
             (async () => {
                 try {
-                    while(true) {
-                        const response = await relay.nextJsonRpcResponse();
+                    for await (const response of relay.jsonRpcResponses) {
                         connection.send(response);
                     }
                 } catch(_error) {}

wasm-node/javascript/src/internals/client.ts

@@ -552,27 +552,41 @@ export function start(options: ClientOptions, wasmModule: SmoldotBytecode | Prom
                         default: throw new Error("Internal error: unknown json_rpc_send error code: " + retVal)
                     }
                 },
+                jsonRpcResponses: {
+                    next: async () => {
+                        while (true) {
+                            if (!state.chains.has(chainId))
+                                return { done: true, value: undefined };
+                            if (options.disableJsonRpc)
+                                throw new JsonRpcDisabledError();
+                            if (state.instance.status === "destroyed")
+                                throw state.instance.error;
+                            if (state.instance.status !== "ready")
+                                throw new Error(); // Internal error. Never supposed to happen.
+
+                            // Try to pop a message from the queue.
+                            const message = state.instance.instance.peekJsonRpcResponse(chainId);
+                            if (message)
+                                return { done: false, value: message };
+
+                            // If no message is available, wait for one to be.
+                            await new Promise<void>((resolve) => {
+                                state.chains.get(chainId)!.jsonRpcResponsesPromises.push(resolve)
+                            });
+                        }
+                    },
+                    [Symbol.asyncIterator]() {
+                        return this
+                    }
+                },
                 nextJsonRpcResponse: async () => {
-                    while (true) {
-                        if (!state.chains.has(chainId))
-                            throw new AlreadyDestroyedError();
-                        if (options.disableJsonRpc)
-                            return Promise.reject(new JsonRpcDisabledError());
-                        if (state.instance.status === "destroyed")
-                            throw state.instance.error;
-                        if (state.instance.status !== "ready")
-                            throw new Error(); // Internal error. Never supposed to happen.
+                    const result = await newChain.jsonRpcResponses.next();
 
-                        // Try to pop a message from the queue.
-                        const message = state.instance.instance.peekJsonRpcResponse(chainId);
-                        if (message)
-                            return message;
-
-                        // If no message is available, wait for one to be.
-                        await new Promise<void>((resolve) => {
-                            state.chains.get(chainId)!.jsonRpcResponsesPromises.push(resolve)
-                        });
+                    if (result.done) {
+                        throw new AlreadyDestroyedError();
                     }
+
+                    return result.value;
                 },
                 remove: () => {
                     if (state.instance.status === "destroyed")

wasm-node/javascript/src/public-types.ts

@@ -177,6 +177,20 @@ export interface Chain {
      */
     nextJsonRpcResponse(): Promise<string>;
 
+    /**
+     * JSON-RPC responses or notifications async iterable.
+     *
+     * Each chain contains a buffer of the responses waiting to be sent out. Iterating over this
+     * pulls one element from the buffer. If the iteration happen at a slower rate than
+     * responses are generated, then the buffer will eventually become full, at which point calling
+     * {@link Chain.sendJsonRpc} will throw an exception. The size of this buffer can be configured
+     * through {@link AddChainOptions.jsonRpcMaxPendingRequests}.
+     *
+     * @throws {@link JsonRpcDisabledError} If the JSON-RPC system was disabled in the options of the chain.
+     * @throws {@link CrashError} If the background client has crashed.
+     */
+    readonly jsonRpcResponses: AsyncIterableIterator<string>
+
     /**
      * Disconnects from the blockchain.
      *