== Motivation ==
On a local dev wiki and in CI, where no gadgets are defined yet,
fetchStructuredList() is called on every load.php request and doing
uncached database look ups. This is because T39228 (stale cache
after Gadgets-definition was empty or created) was fixed by disabling
the cache until the page exists. This seems like a poor solution,
and commit I3092bcb162d032 recognises that the problem was not
understood at the time. I propose to instead cache it always and
purge it when the page is modified in any way.
Cold calling fetchStructuredList() accounted for ~170ms of ~400ms
when trying out debug v2 (T85805), thus making it significantly
slower and causing a chain of dozens of requests to pile up.
== Previously ==
* Legacy repo (MediaWikiGadgetsDefinitionRepo) only implemented
handlePageUpdate.
* handlePageUpdate was called from onPageSaveComplete for both
any page edit, and for creations in the experimental namespace.
* The experimental GadgetDefinitionNamespaceRepo is based on
ContentHandler rather than global hooks. This system does not
have a create-specific callback. It called update for edit/create,
and delete for delete. The experimental repo relied on create being
called from the global hook for the legacy repo, and update was
then called twice.
* There was no global hook for onPageDeleteComplete, thus the
legacy repo did not get purges.
== Changes ==
* Add onPageDeleteComplete hook to fix purges after deletion,
with the legacy repo now implementing handlePageDeletion() and doing
the same as handlePageUpdate().
* Fix handlePageUpdate() docs to reflect that it covers page create,
since onPageSaveComplete() called it either way.
* Fix experimental repo to include its namespace purge in
its handlePageUpdate() method.
* Get rid of now-redundant handlePageCreation().
* Get rid of handlePageDeletion() since its implementations would
now be identical to handlePageUpdate().
All these hooks and handle*() methods are just for a memc key
holding gadget metadata. We don't need to microoptimise this
on a per-page basis. Gadget edits are rare enough that purging them
as a whole each time is fine. We do the same in MediaWiki core
with ResourceLoaderGadgetsModule already.
Bug: T85805
Change-Id: Ib27fd34fbfe7a75c851602c8a93a2e3e1f2c38a0
