Proposal: Re-evaluate userScript and userStyle API

[erosman]

Proposal: Re-evaluate userScript and userStyle API

scripting in manifest v3 removed the code property which was available in contentScripts (and Firefox MV2 userScripts) API.

Requirements

UserScript and UserStyle managers require:

• Both js and css properties
• code property in above in order to function
• An array of objects to include more than one (file and/or code) at a time
• Access to "MAIN", "ISOLATED" & "USER_SCRIPT" execution worlds
• executeScript() & insertCSS() APIs

Having a separate API to inject js and css results in having to make 2 almost identical registrations which would be less efficient for both the browser and the manager.

footnote: scripting.register() namespace could be more inclusive than the literal scripting.registerContentScripts().

Proposal

In order to facilitate both the userScript and the userStyle managers, a combined API would be more efficient.

In fact, the new API would need to be a duplicate of the scripting API with some minor changes, e.g. a flag/permission to enable code inclusion.

See also

#279, #284, #477

[Rob--W]

As written in the meeting notes of today's meeting, it was Chrome's design request to have intentionally separate namespaces for the userScripts functionality. Merging the namespaces is therefore unlikely.

There was some further discussion on the support of "css". While not opposed, we'd like to see actual demand for the feature before considering its support.

P.S. The "userScripts" MDN link in the issue links to Firefox's MV2-only userScripts API. That is separate from the userScripts API that has been designed in #279 and whose proposal was posted at https://github.com/w3c/webextensions/blob/main/proposals/user-scripts-api.md

[erosman]

Namespace

As written in the meeting notes of today's meeting, it was Chrome's design request to have intentionally separate namespaces for the userScripts functionality. Merging the namespaces is therefore unlikely.

That was not part of the proposal.
The proposal mentioned the API would be an almost duplicate of the scripting API with some minor changes/additions.

CSS

There was some further discussion on the support of "css". While not opposed, we'd like to see actual demand for the feature before considering its support.

What about user-style managers?

Since scripting in manifest v3 removed the code property, and user-style managers require that property, unless the intention is to create another API (e.g. userStyles API), then a combined API would be the obvious choice.

Furthermore, scripting API has both JS & CSS in order to handle various situations and user-script & user-style managers require the same (for the same reasons).

The issue was also brought up in the early days of the Firefox MV2 userScripts API development in Bug 1437098.

Array of Objects

An array of objects to include more than one (file and/or code) at a time

Above (important) issue seem to have been missed.

// Must specify exactly one of: `file` or `code`.
dictionary ScriptSource {
  string? code;
  string? file;
}

ScriptSource

code
string optional
A string containing the JavaScript code to inject. Exactly one of file or code must be specified.

file
string optional
The path of the JavaScript file to inject relative to the extension's root directory. Exactly one of file or code must be specified.

Statistics

	user-script	user-style	Chrome Users	Firefox Users	Edge Users	Opera Users
Tampermonkey	✅		11m	670k	10m	3.5m
Violentmonkey	✅		900k	79k	600k
Greasemonkey	✅			203k
FireMonkey	✅	✅		1.5k
Stylish		✅	2m	41k	10k
Stylus		✅	700k	87k
xStyle		✅	60k	290

---

P.S. The "userScripts" MDN link in the issue links to Firefox's MV2-only userScripts API.

Post updated for clarification.

[mon-jai]

@erosman As a workaround, maybe we can create custom style tags with the userscript API?