wasm-action

Wasm-action facilitates the creation, distribution and generic utilization of non-browser based WebAssembly workloads through a local-first approach with a focus on privacy and security. Written primarily in Python, it also explores the Python ecosystem's maturity for WebAssembly and beyond.

Features

• Versatile use as GitHub action, CLI or Python library.
• Supported registries: wa.dev
• Supported artifact types: wasm
• Supported actions: push, pull
• Supports Python 3.10+ on Linux, MacOS and Windows
• Python sandbox for running untrusted code

Planned

• OCI registry support (a.k.a. Docker registry)

Usage

Pull from registry

      - uses: xelato/wasm-action@main
        with:
          action: pull
          registry: wa.dev
          package: component-book:adder

To pull a private package, define your token:

        env:
          WARG_TOKEN: ${{ secrets.WARG_TOKEN }}

Push to registry

      - uses: xelato/wasm-action@main
        with:
          action: push
          registry: wa.dev
          package: foo:bar@1.2.3
          path: files/foo_bar_1.2.3.wasm
        env:
          WARG_TOKEN: ${{ secrets.WARG_TOKEN }}
          WARG_PRIVATE_KEY: ${{ secrets.WARG_PRIVATE_KEY }}

CLI

The tool can be run without installing, using uv/uvx.

$ uvx wasm-action --help          
Usage: wasm-action [OPTIONS] COMMAND [ARGS]...

Options:
  --help  Show this message and exit.

Commands:
  eval     Expression evaluator
  key      Generate private key or read one from stdin
  pull     Pull from registry
  push     Push to registry
  python   Python in a sandbox
  version  Print version
  x        Run a WebAssembly file

$ uvx wasm-action pull --registry wa.dev --package wasi:io
registry=wa.dev
registry-type=warg
warg-url=https://warg.wa.dev
package=wasi:io@0.2.0
package-namespace=wasi
package-name=io
package-version=0.2.0
digest=sha256:c33b1dbf050f64229ff4decbf9a3d3420e0643a86f5f0cea29f81054820020a6
filename=wasi:io@0.2.0.wasm

$ file wasi:io@0.2.0.wasm 
wasi:io@0.2.0.wasm: WebAssembly (wasm) binary module version 0x1000d

$ export WARG_TOKEN="..."
$ export WARG_PRIVATE_KEY="..."
$ uvx wasm-action push -r wa.dev -p foo:bar@1.2.3 --path foo_bar_1.2.3.wasm

$ uvx wasm-action key
{
    "private": "ecdsa-p256:9y5nigLvFp3KZZQtuvN9DchpGIMUB4bwGAtkIoOCla4=",
    "public": "ecdsa-p256:AvspSQWBK65ItTou/uVCi5qC4P+HBCi4R34OIPb3ILRl",
    "id": "sha256:c836bd8a3082f2e8d70bdfa48296e580ab847fcdeadb351f448d03f152d44093"
}

# use private key to configure in github or save it elsewhere in a secure manner
$ uvx wasm-action key | jq .private | pbcopy

# use corresponding public key for new token registration at wa.dev
$ pbpaste | uvx wasm-action key | jq .public

Use as Library

The package is published to the Python Package Index and can be installed/depended-on under the name wasm-action on all supported Python versions.

$ pip install wasm-action

>>> import wasm_action as wa
>>> wa.pull('wa.dev', 'wasi:io')
PackageDownload(namespace='wasi', name='io', version='0.2.0', content='...', digest='sha256:c33b1dbf050f64229ff4decbf9a3d3420e0643a86f5f0cea29f81054820020a6')

However, the library interface is not yet standardised and may (and will!) change.

Python Sandbox

Experimental support for running a WASI build of python/cpython@3.14.

$ uvx --python 3.14 wasm-action python --version
Python 3.14.2+

The characters -- can be used to separate host from guest options in cases where there's ambiguity:

# get guest interpreter help
$ uvx --python 3.14 wasm-action python -- --help

Host Python

The Python interpreter used to run wasm-action. It orchestrates and mediates the guest Python execution under a supported WebAssembly Runtime (wasmtime).

Guest Python

The Python interpreter that was compiled to WebAssembly. Guest Python runs in a restricted "sandbox" environment. In addition to the .wasm module file, it also requires the Python standard library folder, currently being reused from the host Python installation.

Interpreter

Currently there is a choice between --interpreter cpython (default) and --interpreter monty.

Layout

Guest code has access to the following paths:

• / - host's current working directory (read/write)
• /usr/local/lib/python3.14 - host Python's stdlib (read only)
• /tmp (read/write)

Environment variables

Code running in the guest environment only has access to the environment variables explicitly defined:

>>> import os
>>> os.environ
environ({'PYTHONPATH': '/usr/local/lib/python3.14:/build'})

Additional variables can be defined with the -e/--env option.

Packages

Limitations

Application

Running untrusted code, such as one generated by an LLM.