How to Inject a Global with Web Extensions in Manifest V3

Date:


For those of you not familiar with the world of web extension development, a storm is brewing with Chrome. Google will stop support for manifest version 2, which is what the vast majority of web extensions use. Manifest version 3 sees many changes but the largest change is moving from persistent background scripts to service workers. This…is…a…massive…change.

Changes from manifest version 2 to version 3 include:

  • Going from persistent background script to a service worker that can die after 5 minutes
  • No use of <iframe> elements or other DOM APIs from the service worker
  • All APIs have become Promise-based
  • Restrictions on content from a CSP perspective

One function that web extensions often employ is executing scripts upon each new page load. For a web extension like MetaMask, we need to provide a global window.ethereum for dApps to use. So how do we do that with manifest version 3?

As of Chrome v102, developers can define a world property with a value of isolated or main (in the page) for content scripts. While developers should define content_scripts in the extension’s manifest.json file, the main value really only works (due to a Chrome bug) when you programmatically define it from the service worker:

await chrome.scripting.registerContentScripts([
  {
    id: 'inpage',
    matches: ['http://*/*', 'https://*/*'],
    js: ['in-page.js'],
    runAt: 'document_start',
    world: 'MAIN',
  },
]);

In the example above, in-page.js is injected and executed within the main content tab every time a new page is loaded. This in-page.js file sets window.ethereum for all dApps to use. If the world is undefined or isolated, the script would still execute but would do so in an isolated environment.

Manifest version 3 work is quite the slog so please hug your closest extension developer. There are many huge structural changes and navigating those changes is a brutal push!



Source link

Share post:

Subscribe

spot_imgspot_img

Popular

More like this
Related

Covid protests widen in China after Urumqi fire

It has become the latest tipping point in...

Microsoft Bing Promoting TikTok In Search Results

Microsoft Bing seems to...

Jump 7 Years Ahead of People

When you played video games as a kid,...