Single-file JS-only file has reference to non-existing .wasm file (since 4.0.6)

[pasieronen]

I'm building a single-file JS-only file (-sWASM=0 -sSINGLE_FILE=1), which eventually gets bundled with Webpack. With 4.0.5 everything works fine, but with 4.0.6, the resulting .js file has a reference to a .wasm file (which obviously does not exist with these options), and Webpack chokes on that.

The probable culprit is commit 975084c.

How to reproduce:

adder.c

int add(int a, int b) { return a + b; }

index.js

import createAdder from './adder.mjs'
(async () => {
  const Module = await createAdder()
  const add = Module.cwrap("add", "number", ["number","number"]);
  alert("2+3 = " + add(2, 3))
})();

webpack.config.cjs

module.exports = {
  mode: "development",
  entry: "./index.js",
  output: {filename: "bundle.js", path: __dirname}
}

Commands:

emcc -sENVIRONMENT=web -sWASM=0 -sMODULARIZE=1 -sEXPORT_ES6=1 -sSINGLE_FILE=1 -sEXPORTED_FUNCTIONS='["_add"]' -sEXPORTED_RUNTIME_METHODS='["cwrap", "ccall"]'  adder.c -o adder.mjs
# succeeds, nothing special in output

npx webpack-cli@6.0.1
# fails with "Module not found: Error: Can't resolve 'adder.wasm' ...'

Version of emscripten/emsdk:

emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 4.0.6 (1ddaae4)
clang version 21.0.0git (https:/github.com/llvm/llvm-project 4775e6d9099467df9363e1a3cd5950cc3d2fde05)
Target: wasm32-unknown-emscripten
Thread model: posix
InstalledDir: (omitted)

[sbc100]

Can you confirm if it happens with the latest release too? (emsdk install tot or emsdk install 4.0.13)

[pasieronen]

Yes, this happens with 4.0.13, too.

[sbc100]

Thanks, I was able to reproduce locally. In practice the URL is not actually used, but the bundler still sees it. I will see I can find a way to omit this.

[sbc100]

BTW, do you know that you can use -sSINGLE_FILE without using -sWASM=0.. in this case the wasm binary gets embedded in the JS file as base64. This will be better in almost all cases that using wasm2js (-sWASM=0). Is there some reason you need to use wasm2js in you use case?