The best way to Inject a World with Internet Extensions in Manifest V3

For these of you not conversant in the world of net extension improvement, a storm is brewing with Chrome. Google will cease help for manifest model 2, which is what the overwhelming majority of net extensions use. Manifest model 3 sees many modifications however the largest change is transferring from persistent background scripts to service staff. This…is…a…huge…change.

Adjustments from manifest model 2 to model 3 embody:

• Going from persistent background script to a service employee that may die after 5 minutes
• No use of <iframe> parts or different DOM APIs from the service employee
• All APIs have turn into Promise-based
• Restrictions on content material from a CSP perspective

One perform that net extensions typically make use of is executing scripts upon every new web page load. For an internet extension like MetaMask, we have to present a world window.ethereum for dApps to make use of. So how will we do this with manifest model 3?

As of Chrome v102, builders can outline a world property with a worth of remoted or principal (within the web page) for content material scripts. Whereas builders ought to outline content_scripts within the extension’s manifest.json file, the principal worth actually solely works (as a result of a Chrome bug) once you programmatically outline it from the service employee:

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

Within the instance above, in-page.js is injected and executed inside the primary content material tab each time a brand new web page is loaded. This in-page.js file units window.ethereum for all dApps to make use of. If the world is undefined or remoted, the script would nonetheless execute however would achieve this in an remoted setting.

Manifest model 3 work is sort of the slog so please hug your closest extension developer. There are numerous big structural modifications and navigating these modifications is a brutal push!