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Synchronously importing wasm modules in the main chunk #6615

alexcrichton opened this Issue Feb 28, 2018 · 3 comments


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4 participants

alexcrichton commented Feb 28, 2018

Do you want to request a feature or report a bug?


What is the current behavior?

Currently when a wasm module is imported like:

import { foo } from './foo.wasm';
// ...

then wepack will report "Sync WebAssembly compilation is not yet implemented"

If the current behavior is a bug, please provide the steps to reproduce.

$ cat foo.wat
  (type (;0;) (func))
  (func (;0;) (type 0)
  (memory (;0;) 17)
  (export "memory" (memory 0))
  (export "foo" (func 0)))
$ wat2wasm foo.wat -o foo.wasm
$ cat index.js
import { foo } from './foo.wasm';
$ yarn run webpack index.js
yarn run v1.3.2
warning package.json: No license field
$ /home/alex/code/wasm-bindgen/js-hello-world/node_modules/.bin/webpack index.js
Hash: 64205dfbff78f2176ada
Version: webpack 4.0.1
Time: 64ms
Built at: 2018-2-27 19:15:17
Entrypoint main =
   [0] ./foo.wasm 17.5 KiB {0} [built]
   [1] ./index.js 34 bytes {0} [built]

WARNING in configuration
The 'mode' option has not been set. Set 'mode' option to 'development' or 'production' to enable defaults for this environment. 

ERROR in chunk main [entry]
Sync WebAssembly compilation is not yet implemented
error Command failed with exit code 2.
info Visit for documentation about this command.

What is the expected behavior?

Both import('./foo.wasm') and import { foo } from './foo.wasm'; to work. It looks like this is intentionally unimplemented though, so I was wondering if it'd be good to have a tracking issue for this feature? Or maybe such an issue already exists!

If this is a feature request, what is motivation or use case for changing the behavior?

Please mention other relevant information such as the browser version, Node.js version, webpack version, and Operating System.


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sendilkumarn commented Feb 28, 2018

Yes, it is not implemented currently. But it is very much in the cards IIUC

@alexcrichton alexcrichton changed the title from Synchronously importing wasm modules to Synchronously importing wasm modules in the main chunk Mar 3, 2018


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alexcrichton commented Mar 3, 2018

I've updated the issue title to specifically refer to the main check as @sendilkumarn points out that synchronous imports are supported in non-main chunks!


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camerondavison commented May 19, 2018

is this fixed, i was able to build a dist/main.js following these steps.

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