Change 184003 had a related patch set uploaded (by Legoktm):
Load extensions using wfLoadExtensions() if possible

https://gerrit.wikimedia.org/r/184003

Patch-For-Review

The jobs that tests multiple extensions together ( mediawiki-extensions-{hhvm,zend} ), clone a varying list of extension to the workspace. The workspace is NOT cleared between run to avoid cloning over and over all the repositories.

The job craft a list of extensions to load which are listed in a file extensions_load.txt. In LocalSettings.php we inject custom code 50_mw_ext_loader.php which reads the file and attempt to load the default PHP entry point.

As I understand it, wfLoadExtensions() would end up loading any present extension under /extensions/ and since the workspace is not cleaned that would include extensions we don't actually want to test in that specific build :-/

What we will want, is to have the Job start with a clean workspace, clone the extension that have been defined to be tested for that run then use the wfLoadExtensions(). That would require CI to figure out a solution to clone the repositories faster (most probably from a local cache/copy of the repos) and most probably ends up depending on migrating to disposable instances.

In T86359#981543, @hashar wrote:

As I understand it, wfLoadExtensions() would end up loading any present extension under /extensions/ and since the workspace is not cleaned that would include extensions we don't actually want to test in that specific build :-/

No, that's not what it does. It only loads the extensions that are passed to it as a parameter. In my patch, it basically changes require_once lines into wfLoadExtensions(...);. So even if an extension is cloned, as long as it is not passed to the function, it won't be loaded.

Change 184003 merged by jenkins-bot:
Load extensions using wfLoadExtensions() if possible

https://gerrit.wikimedia.org/r/184003