fix: allow getPlatformProxy to handle RPC calls returning objects

allow the `getPlatformProxy` to handle RPC calls returning objects by making
sure that the miniflare magic proxy can take into account methods set via
symbols (in the case or RPC objects specifically `Symbol.dispose` and `Symbol.asyncDispose`)

additionally add more RPC test coverage in miniflare

.changeset/polite-dodos-happen.md

@@ -0,0 +1,9 @@
+---
+"miniflare": patch
+---
+
+fix: Allow the magic proxy to proxy objects containing functions indexed by symbols
+
+In https://github.com/cloudflare/workers-sdk/pull/5670 we introduced the possibility
+of the magic proxy to handle object containing functions, the implementation didn't
+account for functions being indexed by symbols, address such issue

fixtures/get-platform-proxy/tests/get-platform-proxy.env.test.ts

@@ -188,9 +188,15 @@ describe("getPlatformProxy - env", () => {
 			rpc = env.MY_RPC as unknown as EntrypointService;
 			return dispose;
 		});
-		it("can call RPC methods directly", async () => {
+		it("can call RPC methods returning a string", async () => {
 			expect(await rpc.sum([1, 2, 3])).toMatchInlineSnapshot(`6`);
 		});
+		it("can call RPC methods returning an object", async () => {
+			expect(await rpc.sumObj([1, 2, 3, 5])).toEqual({
+				isObject: true,
+				value: 11,
+			});
+		});
 		it("can call RPC methods returning a Response", async () => {
 			const resp = await rpc.asJsonResponse([1, 2, 3]);
 			expect(resp.status).toMatchInlineSnapshot(`200`);

fixtures/get-platform-proxy/workers/rpc-worker/index.ts

@@ -12,6 +12,14 @@ export class NamedEntrypoint extends WorkerEntrypoint {
 	sum(args: number[]): number {
 		return args.reduce((a, b) => a + b);
 	}
+
+	sumObj(args: number[]): { isObject: true; value: number } {
+		return {
+			isObject: true,
+			value: args.reduce((a, b) => a + b),
+		};
+	}
+
 	asJsonResponse(args: unknown): {
 		status: number;
 		text: () => Promise<string>;

packages/miniflare/src/workers/core/proxy.worker.ts

@@ -69,7 +69,15 @@ function isPlainObject(value: unknown) {
 	);
 }
 function objectContainsFunctions(obj: Record<string, unknown>): boolean {
-	for (const [, entry] of Object.entries(obj)) {
+	const propertyNames = Object.getOwnPropertyNames(obj);
+	const propertySymbols = Object.getOwnPropertySymbols(obj);
+	const properties = [...propertyNames, ...propertySymbols];
+
+	for (const property of properties) {
+		// @ts-ignore - ignoring the following line since TypeScript seems to
+		//              incorrectly error if `property` is a symbol
+		//              (see: https://github.com/Microsoft/TypeScript/issues/24587)
+		const entry = obj[property];
 		if (typeof entry === "function") {
 			return true;
 		}

packages/miniflare/test/index.spec.ts

@@ -821,6 +821,104 @@ test("Miniflare: service binding to named entrypoint", async (t) => {
 	});
 });
 
+test("Miniflare: service binding to named entrypoint that implements a method returning a plain object", async (t) => {
+	const mf = new Miniflare({
+		workers: [
+			{
+				name: "a",
+				serviceBindings: {
+					RPC_SERVICE: { name: "b", entrypoint: "RpcEntrypoint" },
+				},
+				compatibilityFlags: ["rpc"],
+				modules: true,
+				script: `
+				export default {
+					async fetch(request, env) {
+						const obj = await env.RPC_SERVICE.getObject();
+						return Response.json({ obj });
+					}
+				}
+				`,
+			},
+			{
+				name: "b",
+				modules: true,
+				script: `
+					import { WorkerEntrypoint } from "cloudflare:workers";
+					export class RpcEntrypoint extends WorkerEntrypoint {
+						getObject() {
+							return {
+								isPlainObject: true,
+								value: 123,
+							}
+						}
+					}
+				`,
+			},
+		],
+	});
+	t.teardown(() => mf.dispose());
+
+	const bindings = await mf.getBindings<{ RPC_SERVICE: any }>();
+	const o = await bindings.RPC_SERVICE.getObject();
+	t.deepEqual(o.isPlainObject, true);
+	t.deepEqual(o.value, 123);
+});
+
+test("Miniflare: service binding to named entrypoint that implements a method returning an RpcTarget instance", async (t) => {
+	const mf = new Miniflare({
+		workers: [
+			{
+				name: "a",
+				serviceBindings: {
+					RPC_SERVICE: { name: "b", entrypoint: "RpcEntrypoint" },
+				},
+				compatibilityFlags: ["rpc"],
+				modules: true,
+				script: `
+				export default {
+					async fetch(request, env) {
+						const rpcTarget = await env.RPC_SERVICE.getRpcTarget();
+						return Response.json(rpcTarget.id);
+					}
+				}
+				`,
+			},
+			{
+				name: "b",
+				modules: true,
+				script: `
+					import { WorkerEntrypoint, RpcTarget } from "cloudflare:workers";
+
+					export class RpcEntrypoint extends WorkerEntrypoint {
+						getRpcTarget() {
+							return new SubService("test-id");
+						}
+					}
+
+					class SubService extends RpcTarget {
+						#id
+
+						constructor(id) {
+							super()
+							this.#id = id
+						}
+
+						get id() {
+							return this.#id
+						}
+					}
+				`,
+			},
+		],
+	});
+	t.teardown(() => mf.dispose());
+
+	const bindings = await mf.getBindings<{ RPC_SERVICE: any }>();
+	const rpcTarget = await bindings.RPC_SERVICE.getRpcTarget();
+	t.deepEqual(rpcTarget.id, 'test-id');
+});
+
 test("Miniflare: custom outbound service", async (t) => {
 	const mf = new Miniflare({
 		workers: [