wasm_exec.js doesn't play well with CloudFlare workers

[TPXP]

Summary

Trying to import https://github.com/tinygo-org/tinygo/blob/dev/targets/wasm_exec.js in a cloudflare worker results in a weird error

✘ [ERROR] service core:user:my-first-worker: Uncaught RangeError: Maximum call stack size exceeded

    at null.<anonymous> (index.js:1:1) in get
    at null.<anonymous> (index.js:1:1) in get
    at null.<anonymous> (index.js:1:1) in get
    at null.<anonymous> (index.js:1:1) in get
    at null.<anonymous> (index.js:1:1) in get
    at null.<anonymous> (index.js:1:1) in get
    at null.<anonymous> (index.js:1:1) in get
    at null.<anonymous> (index.js:1:1) in get
    at null.<anonymous> (index.js:1:1) in get
    at null.<anonymous> (index.js:1:1) in get

Minimal reproduction

Create a basic CloudFlare worker

npm create cloudflare@latest -- my-first-worker

> npx
> "create-cloudflare" my-first-worker

─────────────────────────────────────────────────────────────────
👋 Welcome to create-cloudflare v2.68.0!
🧡 Let's get started.
📊 Cloudflare collects telemetry about your usage of Create-Cloudflare.

Learn more at: https://github.com/cloudflare/workers-sdk/blob/main/packages/create-cloudflare/telemetry.md
─────────────────────────────────────────────────────────────────
╭ Create an application with Cloudflare Step 1 of 3
│
├ In which directory do you want to create your application?
│ dir ./my-first-worker
│
├ What would you like to start with?
│ category Hello World example
│
├ Which template would you like to use?
│ type Worker only
│
├ Which language do you want to use?
│ lang TypeScript
│
├ Copying template files
│ files copied to project directory
│
├ Updating name in `package.json`
│ updated `package.json`
│
├ Installing dependencies
│ installed via `npm install`
│
├ Do you want to add an AGENTS.md file to help AI coding tools understand Cloudflare APIs?
│ no agents
│
╰ Application created

╭ Configuring your application for Cloudflare Step 2 of 3
│
├ Installing wrangler A command line tool for building Cloudflare Workers
│ installed via `npm install wrangler --save-dev`
│
├ Retrieving current workerd compatibility date
│ compatibility date 2026-05-05
│
├ Generating types for your application
│ generated to `./worker-configuration.d.ts` via `npm run cf-typegen`
│
├ Installing @types/node
│ installed via npm
│
├ Do you want to use git for version control?
│ yes git
│
├ Initializing git repo
│ initialized git
│
├ Committing new files
│ git commit
│
╰ Application configured

╭ Deploy with Cloudflare Step 3 of 3
│
├ Do you want to deploy your application?
│ no deploy via `npm run deploy`
│
╰ Done

Add wasm_exec.js

cd my-first-worker
wget https://github.com/tinygo-org/tinygo/raw/refs/heads/dev/targets/wasm_exec.js

Update index.ts to load wasm_exec.js

bat src/index.ts
───────┬───────────────────────────────────────────────────────────────────────
       │ File: src/index.ts
───────┼───────────────────────────────────────────────────────────────────────
   1   │ /**
   2   │  * Welcome to Cloudflare Workers! This is your first worker.
   3   │  *
   4   │  * - Run `npm run dev` in your terminal to start a development server
   5   │  * - Open a browser tab at http://localhost:8787/ to see your worker in action
   6   │  * - Run `npm run deploy` to publish your worker
   7   │  *
   8   │  * Bind resources to your worker in `wrangler.jsonc`. After adding bindings, a type definition for the
   9   │  * `Env` object can be regenerated with `npm run cf-typegen`.
  10   │  *
  11   │  * Learn more at https://developers.cloudflare.com/workers/
  12   │  */
  13   │
  14 + │ import '../wasm_exec.js';
  15 + │
  16   │ export default {
  17   │     async fetch(request, env, ctx): Promise<Response> {
  18   │         return new Response("Hello World!");
  19   │     },
  20   │ } satisfies ExportedHandler<Env>;

Try to run it with npm run dev. Error above appears

Analysis and workarounds

The error seems to originate from the global.require = require; assignment. Commenting it avoids the issue, and we can replace global.require usages in the file (notably https://github.com/tinygo-org/tinygo/blob/dev/targets/wasm_exec.js#L31 and https://github.com/tinygo-org/tinygo/blob/dev/targets/wasm_exec.js#L539-L540) to use require directly without issues.

A Go package designed to use go in cloudflare workers has implemented similar workarounds, commenting out the sections causing issues https://github.com/syumai/workers/blob/main/cmd/workers-assets-gen/assets/wasm_exec_tinygo.js

Suggested solution

Golang's version has evolved to rely on globalThis instead of the global object, I think TinyGo should make these changes too golang/go@680caf1

Here's a patched file (tested in cloudflare workers) https://gist.github.com/TPXP/9a53501c459f22e3535a8af1b1bbe557

[labulakalia]

try this package https://github.com/syumai/workers

[TPXP]

Thanks for the suggestion. This package doesn't address my needs but I confirm its version of tinygo's wasm_exec.js has patches to get it to work. I've opened this issue to discuss upstreaming some changes or fixing the file so that tinygo's version works directly, which would remove the need for custom patches in this go package.

[aykevl]

If you have a patch, can you make a PR for TinyGo? That would help other people too!