Most accesses to this value (other than technically incorrect use
via WebRequest::getVal), such as in various extensions,
call Action::getActionName($ctx) rather than MediaWiki::getAction
or the new RequestContext::getActionName.
Related changes recently:
* Introduced in 3fdfef96e4 (I1e259b54dca4).
* Primary caller optimised in d7beb0e4ec (I72ffc9f36613bf9).
* Warning for misuse added in Ib9fc34ca64b7c0e89.
This fixes a bug in DerivativeContext, which got exposed by the
ActionTest test cases, which happen to use DerivativeContext and
inheriting from the global RequestContext. That's not ideal for
the test to do, but did luckily help find this bug.
The issue is that when changing the title or wikipage, the action
cache be cleared and re-computed the next time it is accessed.
The RequestContext class (which is also a mutable context) does
the same and that is already covered by tests.
Bug: T314008
Depends-On: I8434442a61449c16981b19935f2dbdf18e4b4e50
Change-Id: I7d40e7ca4878d43fd7d7614d9c8cf8d29a8c7c4b
4ac588c634