Automatically lookup site-specific scriptlets.

[gorhill]

Currently, for many sites a scriptlet from resources.txt is injected. For each such scriptlet, there need to be a ##script:inject(...) filter to make use of the scriptlet. For scriptlets which are meant for specific sites, uBO should look them up automatically without the need for a filter.

For example, I just created a scriptlet in https://github.com/uBlockOrigin/uAssets/blob/master/filters/resources.txt for the site lesechos.fr -- to counter the site's anti-blocker. To make use if the scriptlet for that site, I had to create the filter lesechos.fr##script:inject(lesechos.fr.js). When landing on lesechos.fr, uBO should just automatically lookup for a scriptlet named lesechos.fr.js.

This is a common occurrence, so this will save me from having to create a filter for every instance of site-specific scriplet.

[lewisje]

What if the user wishes to disable injection of that scriptlet, with a rule like lesechos.fr#@#script:inject(lesechos.fr.js)?

[gorhill]

I will implement support for exceptions at the same time -- this has been reported as an issue in the past: uBlockOrigin/uAssets#23.

[gorhill]

Fixed with a7fe367.