Allow setOptions() to set runtime port (#610)

* Allow `setOptions()` to set runtime port

* Automatically pick up existing port when updating

* Only update port, remove 'initial' parameter from update function and use helper function to parse port

* Update packages/miniflare/src/runtime/index.ts

Co-authored-by: MrBBot <[email protected]>

* Add test to ensure port is persisted between updates

---------

Co-authored-by: MrBBot <[email protected]>

Author: GregBrimble

packages/miniflare/src/index.ts

@@ -69,6 +69,7 @@ import {
   Timers,
   defaultTimers,
   formatResponse,
+  maybeApply,
 } from "./shared";
 import { Storage } from "./storage";
 import { CoreHeaders } from "./workers";
@@ -468,7 +469,7 @@ export class Miniflare {
     this.#removeRuntimeExitHook = exitHook(() => void this.#runtime?.dispose());
 
     // Update config and wait for runtime to start
-    await this.#assembleAndUpdateConfig(/* initial */ true);
+    await this.#assembleAndUpdateConfig();
   }
 
   async #handleLoopbackCustomService(
@@ -781,12 +782,14 @@ export class Miniflare {
     return { services: Array.from(services.values()), sockets };
   }
 
-  async #assembleAndUpdateConfig(initial = false) {
+  async #assembleAndUpdateConfig() {
+    const initial = !this.#runtimeEntryURL;
     assert(this.#runtime !== undefined);
     const config = await this.#assembleConfig();
     const configBuffer = serializeConfig(config);
     const maybePort = await this.#runtime.updateConfig(configBuffer, {
       signal: this.#disposeController.signal,
+      entryPort: maybeApply(parseInt, this.#runtimeEntryURL?.port),
     });
     if (this.#disposeController.signal.aborted) return;
     if (maybePort === undefined) {

packages/miniflare/src/runtime/index.ts

@@ -70,12 +70,15 @@ export interface RuntimeOptions {
 
 export class Runtime {
   readonly #command: string;
-  readonly #args: string[];
 
   #process?: childProcess.ChildProcess;
   #processExitPromise?: Promise<void>;
 
   constructor(private opts: RuntimeOptions) {
+    this.#command = workerdPath;
+  }
+
+  get #args() {
     const args: string[] = [
       "serve",
       // Required to use binary capnp config
@@ -98,18 +101,21 @@ export class Runtime {
       args.push("--verbose");
     }
 
-    this.#command = workerdPath;
-    this.#args = args;
+    return args;
   }
 
   async updateConfig(
     configBuffer: Buffer,
-    options?: Abortable
+    options?: Abortable & Partial<Pick<RuntimeOptions, "entryPort">>
   ): Promise<number | undefined> {
     // 1. Stop existing process (if any) and wait for exit
     await this.dispose();
     // TODO: what happens if runtime crashes?
 
+    if (options?.entryPort !== undefined) {
+      this.opts.entryPort = options.entryPort;
+    }
+
     // 2. Start new process
     const runtimeProcess = childProcess.spawn(this.#command, this.#args, {
       stdio: ["pipe", "pipe", "pipe", "pipe"],

packages/miniflare/test/index.spec.ts

@@ -55,6 +55,23 @@ test("Miniflare: validates options", async (t) => {
   );
 });
 
+test("Miniflare: keeps port between updates", async (t) => {
+  const opts: MiniflareOptions = {
+    port: 0,
+    script: `addEventListener("fetch", (event) => {
+      event.respondWith(new Response("a"));
+    })`,
+  };
+  const mf = new Miniflare(opts);
+  const initialURL = await mf.ready;
+
+  await mf.setOptions(opts);
+  const updatedURL = await mf.ready;
+
+  t.not(initialURL.port, "0");
+  t.is(initialURL.port, updatedURL.port);
+});
+
 test("Miniflare: routes to multiple workers with fallback", async (t) => {
   const opts: MiniflareOptions = {
     workers: [