parcel-resolver-inlinefunc

A Parcel resolver that allows you to compile an imported default function into an IIFE (using esbuild) and wrap it in a function accepting variadic args, which forwards them to the original function when executed.

This allows you to create a serializable function (bundling all necessary dependencies within itself) that can be deserialized and executed in a different context, such as a Chrome content script, a web worker, or a Javascript VM.

You can see a real example of this being used in browser-extension-for-opentelemetry.

Installation

pnpm i -D parcel-resolver-inlinefunc

yarn add -D parcel-resolver-inlinefunc

Usage

background.js:

// import a default function from a file
import contentScript from 'inlinefunc:./content-script';

chrome.tabs.onUpdated.addListener(async (tabId, changeInfo, tab) => {
    if (changeInfo.status === "complete") {
        chrome.scripting.executeScript({
            // use the function as normal
            func: injectContentScript,
            args: [
                chrome.runtime.id,
                // ...any other args
            ],
            target: { tabId, allFrames: true },
            injectImmediately: true,
            world: "MAIN"
        })
    }
})

content-script.js:

import * as _ from 'lodash/string'

// IMPORTANT: function must be the default export
export default async function main(extensionId: string) {
    const example = `hey there extension: ${extensionId}!`
    console.log(_.kebabCase(example))
}

Customization

If you'd like to pass anything else to esbuild (see the default parameters here), for example if your function requires any polyfills, you can do so by creating an inlinefunc.config.mjs file (or whatever you'd like to name it) which exports a default object of the top-level configuration options you'd like to override:

inlinefunc.config.mjs

import { polyfillNode } from "esbuild-plugin-polyfill-node";

export default {
    plugins: [
        polyfillNode({
            path: true,
        })
    ]
};

You can then use this file by referencing it in your package.json:

package.json

{
  "name": "my-package",
  "version": "1.0.0",
  ...
  "devDependencies": {
    "parcel-resolver-inlinefunc": "^1.0.0"
  },
  "parcel-resolver-inlinefunc": {
    "options": "inlinefunc.config.mjs"
  }
}

Known issues

Uncaught TypeError: Failed to construct 'URL': Invalid URL

If you're attempting to use a library that imports WebAssembly (resulting in a call like new URL("*.wasm", import_meta.url).href;), this is currently unsupported, but likely fixable.

Cannot find module 'inlinefunc:*' or its corresponding type declarations.

If you're using TypeScript, you'll need to declare the module in a .d.ts file:

declare module "inlinefunc:*" {
    const inlinefunc: (...args: any[]) => void;
    export default inlinefunc;
}