Why:
* ServiceWiring.php is documented to say that "Services MUST NOT
vary their behaviour on the global state, especially not ...
RequestContext ... or ... "current" user"
** However, the constructor of the CommentParserFactory calls
`RequestContext::getMain()->getLanguage()` which is in
violation of this rule by both using the RequestContext
and being controlled by the state of the "current" user.
* This has caused issues with premature access to the session
user as demonstrated in T397900.
** Specifically, the call to ::getLanguage will load the request
user's preferences and then as part of this checks if the
user is named (which will load the User object).
* Instead of using the incorrect method of getting the user's
language, it should instead be fetched in
CommentParserFactory::create.
** This will also allow the Language associated with the main
request to change without leaving the service with an
outdated and stale version of the user's Language object.
What:
* Update CommentParserFactory to call `RequestContext::getMain()
->getLanguage()` in the ::create method instead of getting it
from the constructor.
* Remove the call to `RequestContext::getMain()->getLanguage()`
in ServiceWiring.php as no longer needed.
* Update the unit test to instead be an integration test due to
::create now calling code which uses the service container.
Bug: T397900
Change-Id: I36c9d8650eb5040f94626fa50f90b8026d3c3fe9
(cherry picked from commit 536f41bce51ca67733c4879d17992ee0b0db1de8)
05631d4fe4