Support uploading a pre-built WASM module

[GregBrimble]

💡 Feature request

Overview and problem statement

Right now, wrangler supports the building a WASM module as part of the build and upload process with type = "rust", but does not support uploading a pre-built WASM module. I propose adding a new key to the wrangler configuration to allow developers to specify the filepath location of any modules they want to bind (similar to how they already specify the webpack_config location). I imagine it would work similar to kv_namespaces.

Basic example

# wrangler.toml
name = "$SCRIPT_NAME"
type = "webpack"
account_id = "$ACCOUNT_ID"
workers_dev = true

# Just as webpack config files are located like this,
webpack_config = "./webpack.config.js"

# and KV namespaces are configured in an array like this,
kv_namespaces = [
  { binding = "FOO", id = "0f2ac74b498b48028cb68387c421e279", preview_id = "6a1ddb03f3ec250963f0a1e46820076f" },
  { binding = "BAR", id = "068c101e168d03c65bddf4ba75150fb0", preview_id = "fb69528dbc7336525313f2e8c3b17db0" }
]

# WASM modules could be configured as follows:
wasm_modules = [
  { binding = "MYWASM", location = "./my_wasm_file.wasm" }
]

Wrangler would simply have to locate the file, reference it in the metadata, and upload it alongside the script as a part of the PUT call to upload a new worker.

[koeninger]

Have you seen #1677

[GregBrimble]

Ah, sweet! Didn't realize that PR will solve this too. Thanks for highlighting that, @koeninger.

[xtuc]

@GregBrimble since you are using the webpack type, https://github.com/cloudflare/worker-emscripten-template/blob/master/webpack.config.js#L24-L31 should fix your issue. It needs to be located at a specific path to get uploaded by wrangler. I don't think #1677 will fix that.

[GregBrimble]

Amazing—thanks for that example, @xtuc! If #1677 doesn't address it, and there's interest for what I'm proposing, I'd be happy to try make a PR. Anyone on the wrangler team able to say if that's something they'd like to support?

[xortive]

#1677 does in fact support uploading pre-built wasm modules.

[sepbot]

#1677 does in fact support uploading pre-built wasm modules.

how do we upload pre-built wasm modules? It's not clear from the PR and not documented anywhere...

Using the API directly I can put this in the metadata.json and refer to WASM global variable (not using modules)

{
    "type": "wasm_module",
    "name": "WASM",
    "part": "wasm"
  }

How does one declare this in wrangler.toml when using modules?

I have tried arbitrarily throwing the pre-built WASM module in folder declared build.upload_dir (when build.upload_format = "modules") and I end up with this error:

 {
  "result": null,
  "success": false,
  "errors": [
    {
      "code": 10013,
      "message": "workers.api.error.unknown"
    }
  ],
  "messages": []
}

If I remove the WASM file from the above it succeeds, if I upload the same file to a non-module worker it still succeeds.

Some description or an example indicating how it's supposed to work would be appreciated.

[jmonster]

@xortive @koeninger would either of you happen to know the answer to @sepbot 's last question?

I've been scouring the web trying to figure out how (if at all?) I can use ffmpeg.wasm or ffmpeg.js in a worker

---

It seems like it should just work by importing it like anything else? but wrangler dev pegs the CPU at 100% for along while and then crashes with JS heap out of memory. This seems to perhaps be a webpack issue rather than a wrangler one -- but if someone could confirm? :)

[robertaboukhalil]

In case it helps, setting wasm_modules = { MYWASM = "./something.wasm" } in wrangler.toml seems to work for me (see example here)