README.md

Terminal Demo

Try the Python-Wasm Live Demos:

• https://cowasm.org (uses Atomics and SharedArrayBuffers)

• https://zython.org (uses Service Workers)

This is a demo of xterm.js and webpack with python-wasm.

Using python-wasm with webpack

You can use python-wasm with webpack5. There are two things you may have to modify in your webpack configuration. See webpack.config.js, in particular:

1. The NodePolyfillPlugin is required because python-wasm uses memfs, which requires several polyfilled libraries.

2. The wasm and zip asset/resource rules are needed so python-wasm can import the python wasm binary and zip filesystem.

Thus your webpack.config.js might include the following:

const NodePolyfillPlugin = require("node-polyfill-webpack-plugin");

module.exports = {
  plugins: [
    new NodePolyfillPlugin(),
  ],
  module: {
    rules: [
      {
        test: /\.wasm$|\.zip$/,
        type: "asset/resource",
      },
    ],
  }
};

Synchronous IO

To use Atomic and SharedArrayBuffer for synchronous IO, your webserver must have the following two headers set:

• Cross-Origin-Opener-Policy: same-origin

• Cross-Origin-Embedder-Policy: require-corp

Your webpack.config.js would then include:

module.exports = {
  // ...
  devServer: {
    headers: {
      "Cross-Origin-Opener-Policy": "same-origin",
      "Cross-Origin-Embedder-Policy": "require-corp",
    },
  },
};

This is optional: if you don't set the headers, then a service worker is used instead to support synchronous IO. No special setup is needed to use the service worker. If you do set these heϨaders, then other things on a complicated website may break since it's a highly restrictive security policy, e.g., GitHub pages does not support this.

Run the demo for yourself

Clone the repo:

git clone https://github.com/sagemathinc/cowasm
cd cowasm/packages/terminal
npm install
npm run serve

Then visit the URL that it outputs, which is probably http://localhost:8080. You can then use Python. In addition the following should work:

• control+c to interrupt running computations

• input('foo') for interactive input

• import time; time.sleep(3) for sleep that doesn't just burn CPU

Do the following to force the fallback to service workers:

SW=true npm run serve

Note that the service worker approach causes a page refresh the very first time the page is loaded, so that the active service worker takes over proxying certain requests.

Supported Platforms: I've tested the above with node v14, v16 and v18 on Linux, MacOS, and Microsoft Windows. On Windows, you have to directly edit webpack.config.js to test out service workers.

Firefox and Service Workers

Unlike Safari and Chrome, Firefox doesn't allow service workers over http without setting dom.serviceWorkers.testing.enabled, so set that to true in about:config to test locally.