I was able to track the issue down to the changes made in this patch:
https://gerrit.wikimedia.org/r/331563
This patch is mostly a simplification of ce8a2d4
(I9a73b3086fc8fb0edd897a347b5497d5362e20ef):
- Don't make wait#wait() abortable. This adds complexity and isn't
needed since the token is rechecked in the .then() of
actions#linkDwell(). The request is permitted to continue and fetch if
that token still matches and is never issued otherwise.
Once a request has been issued, that request is still abortable.
However, note that calling XHR.abort() is just a request to abort and
may not be granted. Whether or not XHR.catch() is invoked is what
dispatches the FETCH_ABORTED action (or doesn't if the request to
abort was denied).
- Remove the abort tests for wait#wait() since the functionality is no
longer provided.
- Pass the preview token in the FETCH_ABORTED action and reduce
FETCH_ABORTED the same way as ABANDON_COMPLETE in reducers/preview.
The follow-up patch, I3597b8025f7a12db0cf5d83cce5a77abace9bae3, adds
integration tests for the specific bug fix. Note that these Selenium
tests are incompatible with the content proxy, so it is probably best to
simply unset $wgPopupsRestGatewayEndpoint and $wgPopupsGateway and allow
the defaults to be used. Also note that the tests are incompatible with
recent versions of Node.js (so use NVM) and emit many deprecation
warnings (so set deprecationWarnings to false in
tests/selenium/wdio.conf.js) An example run of the tests looks something
like:
chromedriver --url-base=wd/hub --port=4444 &
# If any changes are made locally, also run `npm -s start &`.
MW_SERVER=http://localhost:8181 \
MEDIAWIKI_USER=foo \
MEDIAWIKI_PASSWORD=bar \
DISPLAY= \
npm -s run selenium-test
Live testing may be performed as well. Remember that RESTBase requests
are incompatible with MobileFrontend's content proxy hack so ensure to
comment it out if $wgPopupsGateway is configured for RESTBase (see
T218159).
1. Open the DevTools network tab.
2. Disable the browser cache. Chromium, at least, won't abort requests
coming form the cache.
3. Hover back and forth quickly over a preview. In Chromium, canceled
requests are labeled and appear red. This is a good scenario to test.
With the patch, a preview should always be shown when ultimately
resting on a link. Without the patch, it is possible to rest upon the
link with no preview showing. This may require several attempts.
Bug: T219434
Change-Id: I9da84b0296dd14e9ce69cb35f1ca475272fb249a
065a8e9631