I have tested this item ✅ successfully on 6db2cdd

If I rightly remember, Babel doesn't transpile promises unless you're using their polyfill, which I don't think Joomla does

@C-Lodder Is installation/template/js/setup.js transpiled, too? I've never noticed that.

As far as I can see, only stuff below build/media_source is transpiled, to which the installation setup.js does not belong. So for this PR here it seems to be ok.

@richard67 I think it's separate, but @wilsonge requested that ES2013 JS stayed as part of the CMS to support IE11, and Promises are not part of that spec

@C-Lodder I see. Well, maybe George changed opinion ;-) But good that you remind him.

@C-Lodder Well, I just remember IE11 stuff mainly should be kept for 3rd party devs, not for core install, so maybe that's the reason why he uses the promises here.

But I think it could be dangerous: Some people might see it as example which could be used anywhere else and then use it where it should not be used. No idea what's the result if such thing is then transpiled, best would be to have an error, worst would be that it just does nothing.

So I think it is good that you mentioned it here.

I dunno. I mean I hadn’t considered whether the installation should work on IE11 if I’m brutally honest. My gut is it shouldn’t. I’m mostly caring about the front end templates (not even the backend). But willing to listen as to if we should just blanket require Babel (currently we aren’t even running Babel or scss on the installer)

It probably should work just enough to get to a page that says you cant use ie11 and you need to use one of the other browsers that you have on your machine - and not end up like the login screen which is just blank

Ok. In which case you just need to fix the code style

after applying the patch I cannot install joomla.
I have the following error :

Issue #26265 is not resolved.
Applying wrong database credentials does not appears the expected error message.
Instead, it proceeds with the validation of the database and the installation process.

@fotisoikonomou Did you test with the right order of processing? You first have to apply this patch on a 4.0-dev branch of a git clone, or you have to apply it on a 4.0-alpha-12 or nightly build installation, then delete configuration.php and all database tables using PhpMyAdmin or whatever else, then make a new installation with the patched code.

I have tested this item ✅ successfully on ca6a552

After adding the missing { in setup.js the patch works and I can only see the db connection tab to correct the connection

@wilsonge Please fix the conflicts

@wilsonge can you have a look on the conflicts? Should also be rebased to 4.2-dev I guess.

These conflicts are basically unfixible. If someone wants to pick this up then I'm happy with it