mw.loader.state() is added for only=scripts requests, by ResourceLoader::makeModuleResponse().

It does to by calling ResourceLoader::makeLoaderStateScript(), minifying the result, and appending it to $out.

Variable $out at this point is the result of calling ResourceLoaderModule::getModuleContent(), taking the 'scripts' index, and minifying the result.

• getModuleContent() is the public (process-cached) wrapper around ResourceLoaderModule::buildContent which explicitly ensures that scripts ends with a semi-colon and a line-break.

• The minifier we use (JavaScriptMinifier.php), as far as I can tell does not strip semi-colons in any case. I've verified this also with our unit tests.

I found the culprit.

Enabling debug mode on https://meta.wikimedia.org/w/load.php?debug=true&lang=en&modules=ext.globalCssJs.user&only=scripts&skin=vector&user=Magnus+Manske shows the following:

/*
User:Magnus_Manske/global.js
*/
/* .. */

$(document).ready ( function () {
	if ( typeof mw.config.values.wgWikibaseItemId == 'undefined' && mw.config.values.wgAction == 'view' && mw.config.values.wgNamespaceNumber == 0 && mw.config.values.wgDBname != 'wikidatawiki' ) {
		var portletLink = mw.util.addPortletLink( 'p-tb', '#', 'Create Wikidata item','t-wd_create');
		$(portletLink).click ( function () {
			var url = "https://tools.wmflabs.org/wikidata-todo/duplicity.php?wiki=" + mw.config.values.wgDBname + "&page=" + encodeURIComponent(mw.config.values.wgTitle) ;
			window.location.href = url ;
			return false ;
		} ) ;
	}
})

// Wiki-Labels [[File:User:EpochFail/WikiLabels.js]]
//mw.loader.load( '//labels.wmflabs.org/gadget/loader.js' );
mw.loader.state( {
    "ext.globalCssJs.user": "ready"
} );

Note how the "scripts" portion (before the final statement containing mw.loader.state) doesn't end with a real semi-colon token, but with two inline comments.

As such, the logic that is ensuring a semi-colon at the end in ResourceLoaderModule::buildContent(), is fooled. The logic applies PHP trim() and then asserts whether last character is a semi-colon. And indeed, it is, except it's part of the comment.

So no extra separation semi-colon is needed it seems, then it gets minified (which removes the comment), and then we append mw.loader.state().

Change 361622 had a related patch set uploaded (by Krinkle; owner: Krinkle):
[mediawiki/core@master] resourceloader: Add basic tests for getScript() and buildContent()

https://gerrit.wikimedia.org/r/361622

Change 361622 merged by jenkins-bot:
[mediawiki/core@master] resourceloader: Add basic tests for getScript() and buildContent()

https://gerrit.wikimedia.org/r/361622

Change 361806 had a related patch set uploaded (by Krinkle; owner: Krinkle):
[mediawiki/core@master] resourceloader: Add more concat test cases for makeModuleResponse

https://gerrit.wikimedia.org/r/361806

Change 361810 had a related patch set uploaded (by Krinkle; owner: Krinkle):
[mediawiki/core@master] resourceloader: Use "\n" instead of ";" as separator for scripts

https://gerrit.wikimedia.org/r/361810

Change 361806 merged by jenkins-bot:
[mediawiki/core@master] resourceloader: Add more concat test cases for makeModuleResponse

https://gerrit.wikimedia.org/r/361806

Change 361810 merged by jenkins-bot:
[mediawiki/core@master] resourceloader: Use "\n" instead of ";" as separator for scripts

https://gerrit.wikimedia.org/r/361810