Cannot deploy to cloudflare worker when using cloudflare vite / tanstack start (wasm bug?)

[devnomic]

Probably related to wasm

Repo Reproduction:
https://github.com/devnomic/cloudflare-worker-tanstack-restate-bug-repro

Check src/server.ts

Works on npm run dev, but when try to deploy npm run deploy. Cloudflare triggers errors.

  Uncaught TypeError: Cannot read properties of undefined (reading 'set_log_level')
    at null.<anonymous> (index.js:2244:8) in set_log_level
    at null.<anonymous> (index.js:1762:5) in GenericHandler
    at null.<anonymous> (index.js:4526:28) in handler
    at null.<anonymous> (index.js:4554:5) in createEndpointHandler
    at null.<anonymous> (index.js:9275:25)
   [code: 10021]
  To learn more about this error, visit:
  https://developers.cloudflare.com/workers/observability/errors/#validation-errors-10021

  
  If you think this is a bug, please open an issue at:
  https://github.com/cloudflare/workers-sdk/issues/new/choose

This repo is using tanstack which using cloudflare vite plugin, so i'm not sure which part reproducing this bug.

I tried the official example is using raw cloudflare worker / without vite, which is works.

[nikrooz]

This is what I think is the issue:

The SDK has a WASM loader file that initializes the WebAssembly module before re exporting the wasm bindings.

The important bit is the sequence: the file creates a WebAssembly instance, calls imports.__wbg_set_wasm(instance.exports) to wire everything up, and only then does export * from "./sdk_shared_core_wasm_bindings_bg.js". This initialization code needs to run before any of the exported functions can be used.

Vite (and probably other modern bundlers) are being aggressive with optimizations. When they see export * from "...", they might decide to "hoist" that export and link directly to the underlying module, effectively bypassing this loader file entirely. If that happens, the initialization code never runs, and when the app tries to call set_log_level, it's undefined.

The cloudflareWorkersBundlerPatch() trick does not necessarily work with all bundlers.

I believe in dev mode, Vite is more conservative and tends to preserve module execution order. Hence, why it works in dev and not in production.

One way to fix this is to tell the bundler not to optimise the loader, by setting sideEffects in package.json:

{
  "sideEffects": true
}

Or more targeted:

{
  "sideEffects": [
    "{PATH_TO_FILE}/sdk_shared_core_wasm_bindings.js"
  ]
}

[nikrooz]

Until we fix this, this vite config can give you a workaround

import { defineConfig } from "vite";
import { cloudflare } from "@cloudflare/vite-plugin";

export default defineConfig({
  plugins: [cloudflare()],
  build: {
    rollupOptions: {
      plugins: [
        {
          name: "wasm-loader-with-sideEffects",
          transform(code, id) {
            if (id.endsWith("sdk_shared_core_wasm_bindings.js")) {
              return { moduleSideEffects: true };
            }
          },
        },
      ],
    },
  },
});