fix: address review feedback on build and worker startup

- pack-zip: resolve the root with fileURLToPath (import.meta.dirname
  needs Node 20.11+), run in-process and write via temp file + rename
- esbuild: await packing in onEnd so failures exit non-zero and rebuilds
  never pack concurrently; start from a clean dist so stale files are
  not shipped
- main: construct the worker inside try so an unsupported module worker
  shows an error and allows retry instead of leaving init stuck
- worker: only dispatch own action handlers (CodeQL dynamic method call)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: bajrangCoder

esbuild.config.mjs

@@ -1,9 +1,9 @@
-import { execFile } from "node:child_process";
-import { cp, mkdir } from "node:fs/promises";
+import { cp, mkdir, rm } from "node:fs/promises";
 import { createRequire } from "node:module";
 import os from "node:os";
 import path from "node:path";
 import * as esbuild from "esbuild";
+import packZip from "./pack-zip.js";
 
 const require = createRequire(import.meta.url);
 const isServe = process.argv.includes("--serve");
@@ -37,7 +37,9 @@ function serveUrls(hosts, port) {
 	return [...names].map((host) => `http://${host}:${port}`);
 }
 
-async function copyPyodide() {
+// Starts from an empty dist so files from earlier builds are never packaged
+async function prepareDist() {
+	await rm("dist", { recursive: true, force: true });
 	const libDir = path.resolve("dist/lib");
 	await mkdir(libDir, { recursive: true });
 	await Promise.all(
@@ -47,16 +49,6 @@ async function copyPyodide() {
 	);
 }
 
-function packZip() {
-	execFile(process.execPath, ["./pack-zip.js"], (err, stdout) => {
-		if (err) {
-			console.error("Error packing zip:", err);
-			return;
-		}
-		console.log(stdout.trim());
-	});
-}
-
 // Bundles imported CSS (nesting lowered, fonts inlined) and exposes it as a string
 const cssTextPlugin = {
 	name: "css-text",
@@ -85,9 +77,16 @@ const cssTextPlugin = {
 const zipPlugin = {
 	name: "zip-plugin",
 	setup(build) {
-		build.onStart(copyPyodide);
-		build.onEnd((result) => {
-			if (!result.errors.length) packZip();
+		// esbuild waits for this before finishing the build or starting a
+		// rebuild, so packing never overlaps
+		build.onEnd(async (result) => {
+			if (result.errors.length) return;
+			try {
+				await packZip();
+			} catch (error) {
+				console.error("Error packing zip:", error);
+				if (!isServe) process.exitCode = 1;
+			}
 		});
 	},
 };
@@ -114,6 +113,8 @@ const buildConfig = {
 };
 
 (async () => {
+	await prepareDist();
+
 	if (isServe) {
 		console.log("Starting development server...");
 
@@ -129,6 +130,6 @@ const buildConfig = {
 	} else {
 		console.log("Building for production...");
 		await esbuild.build(buildConfig);
-		console.log("Production build complete.");
+		if (!process.exitCode) console.log("Production build complete.");
 	}
 })();

pack-zip.js

@@ -1,84 +1,102 @@
-import fs from "node:fs";
+import fs from "node:fs/promises";
 import path from "node:path";
+import { fileURLToPath } from "node:url";
 import jszip from "jszip";
 
-const root = import.meta.dirname;
-const iconFile = path.join(root, "icon.png");
-const licenseFile = path.join(root, "LICENSE");
-const pluginJSON = path.join(root, "plugin.json");
-const distFolder = path.join(root, "dist");
-const json = JSON.parse(fs.readFileSync(pluginJSON, "utf8"));
-const readmeDotMd = resolveMetadataFile(json.readme, [
-	"readme.md",
-	"README.md",
-]);
-const changelogDotMd = resolveMetadataFile(json.changelogs, [
-	"changelog.md",
-	"changelogs.md",
-	"CHANGELOG.md",
-]);
-
-const zip = new jszip();
-
-zip.file("icon.png", fs.readFileSync(iconFile));
-zip.file("plugin.json", fs.readFileSync(pluginJSON));
-
-if (fs.existsSync(licenseFile)) {
-	zip.file("LICENSE", fs.readFileSync(licenseFile));
-}
+const root = path.dirname(fileURLToPath(import.meta.url));
 
-if (readmeDotMd) {
-	zip.file(
-		json.readme || path.basename(readmeDotMd),
-		fs.readFileSync(readmeDotMd),
-	);
-}
+/**
+ * Packs plugin.json, metadata files and the dist folder into plugin.zip.
+ * The archive is written to a temp file and renamed, so a dev server never
+ * serves a partially written zip.
+ */
+export default async function packZip() {
+	const pluginJSON = path.join(root, "plugin.json");
+	const json = JSON.parse(await fs.readFile(pluginJSON, "utf8"));
+	const readmeDotMd = await resolveMetadataFile(json.readme, [
+		"readme.md",
+		"README.md",
+	]);
+	const changelogDotMd = await resolveMetadataFile(json.changelogs, [
+		"changelog.md",
+		"changelogs.md",
+		"CHANGELOG.md",
+	]);
 
-if (changelogDotMd) {
-	zip.file(
-		json.changelogs || path.basename(changelogDotMd),
-		fs.readFileSync(changelogDotMd),
-	);
-}
+	const zip = new jszip();
 
-loadFile("", distFolder);
+	zip.file("icon.png", await fs.readFile(path.join(root, "icon.png")));
+	zip.file("plugin.json", await fs.readFile(pluginJSON));
 
-zip
-	.generateNodeStream({ type: "nodebuffer", streamFiles: true })
-	.pipe(fs.createWriteStream(path.join(root, "plugin.zip")))
-	.on("finish", () => {
-		console.log("Plugin plugin.zip written.");
-	});
+	const licenseFile = path.join(root, "LICENSE");
+	if (await exists(licenseFile)) {
+		zip.file("LICENSE", await fs.readFile(licenseFile));
+	}
+
+	if (readmeDotMd) {
+		zip.file(
+			json.readme || path.basename(readmeDotMd),
+			await fs.readFile(readmeDotMd),
+		);
+	}
 
-function loadFile(base, folder) {
-	for (const file of fs.readdirSync(folder)) {
+	if (changelogDotMd) {
+		zip.file(
+			json.changelogs || path.basename(changelogDotMd),
+			await fs.readFile(changelogDotMd),
+		);
+	}
+
+	await loadFile(zip, "", path.join(root, "dist"));
+
+	const output = path.join(root, "plugin.zip");
+	const tempOutput = `${output}.tmp`;
+	await fs.writeFile(
+		tempOutput,
+		await zip.generateAsync({ type: "nodebuffer", streamFiles: true }),
+	);
+	await fs.rename(tempOutput, output);
+	console.log("Plugin plugin.zip written.");
+}
+
+async function loadFile(zip, base, folder) {
+	for (const file of await fs.readdir(folder)) {
 		if (file === ".DS_Store" || /LICENSE.txt/.test(file)) continue;
 
 		const filePath = path.join(folder, file);
 		const zipPath = path.posix.join(base, file);
 
-		if (fs.statSync(filePath).isDirectory()) {
+		if ((await fs.stat(filePath)).isDirectory()) {
 			zip.folder(zipPath);
-			loadFile(zipPath, filePath);
+			await loadFile(zip, zipPath, filePath);
 			continue;
 		}
 
-		zip.file(zipPath, fs.readFileSync(filePath));
+		zip.file(zipPath, await fs.readFile(filePath));
 	}
 }
 
-function resolveMetadataFile(configuredPath, fallbacks) {
+async function resolveMetadataFile(configuredPath, fallbacks) {
 	if (configuredPath) {
 		const file = path.join(root, configuredPath);
-		if (!fs.existsSync(file)) {
+		if (!(await exists(file))) {
 			throw new Error(`Missing plugin metadata file: ${configuredPath}`);
 		}
 		return file;
 	}
 
 	for (const fallback of fallbacks) {
 		const file = path.join(root, fallback);
-		if (fs.existsSync(file)) return file;
+		if (await exists(file)) return file;
 	}
 	return null;
 }
+
+async function exists(file) {
+	try {
+		await fs.access(file);
+		return true;
+	} catch {
+		return false;
+	}
+}

plugin.zip

@@ -93,10 +93,11 @@ class Python {
 		this.#state = this.INITIALIZING;
 		this.$page.settitle(strings["loading..."]);
 		this.#worker?.terminate();
-		this.#worker = new Worker(`${this.baseUrl}worker.js`, { type: "module" });
-		this.#worker.onmessage = this.#workerOnMessage.bind(this);
 
 		try {
+			// inside try: construction throws if module workers are unsupported
+			this.#worker = new Worker(`${this.baseUrl}worker.js`, { type: "module" });
+			this.#worker.onmessage = this.#workerOnMessage.bind(this);
 			await new Promise((resolve, reject) => {
 				this.#onInitSuccess = resolve;
 				this.#onInitError = reject;
@@ -116,7 +117,7 @@ class Python {
 		} catch (error) {
 			// allow the next run to retry
 			this.#state = this.NOT_INTIALIZED;
-			this.print(error, "error");
+			this.print(error?.message ?? error, "error");
 			return false;
 		} finally {
 			this.$page.settitle("Python");

src/main.js

@@ -121,7 +121,8 @@ __builtins__.input = input
 self.onmessage = async (e) => {
 	const { action } = e.data;
 
-	if (actions[action]) {
+	// only the handlers defined above, never inherited Object methods
+	if (Object.hasOwn(actions, action)) {
 		await actions[action](e.data);
 	}
 };