A complication is that I'm not entirely clear on how it did work before the bot shut-off. My dev version seems to be expanding citations fine, but I don't see anything in the code that allows checking wikicode (as the second tickybox promises), so I am wondering how that actually functioned.

This is ready for testing on testwiki, as commented here: https://en.wikipedia.org/wiki/User_talk:Citation_bot#Citation_bot_progress. I have disabled the second tickybox until it's clear whether I should figure out how to actually make it allow checking wikicode.

For clarification, the interface that is ready for testing is https://tools.wmflabs.org/citations-dev/doibot.html.

From the on-wiki discussion, it sounds like there are a few bugs to resolve:

• When Unicode U+2019 (right single quotation mark (’)) appears in an author name, it should be replaced with the standard typewriter apostrophe ('), so that it doesn't trigger any script errors.
• When there is an existing author parameter, it should not add a bunch of lastn parameters (https://en.wikipedia.org/wiki/User_talk:Citation_bot#Bot_unnecessarily_adding_last2.2C_last3.2C_last4.2C_..._parameters)
• The {{cite pmid}}, {{cite doi}}, {{cite isbn}}, and {{cite jstor}} templates should be substituted instead of transcluded. (I have no idea which of those are actually used by Citation bot.) See https://www.mediawiki.org/wiki/Manual:Substitution.

If you agree that these are all blockers, we should create sub-tasks for each of them.

I've made tasks for the first two. I'm not sure about the third--discussion seems to be ongoing in the RfCs in this notice and I'm not clear on what that implies for this bot. Citation bot already uses the pmid, doi, and jstor templates.

Removed blocking tasks, which more properly belong to T110776.

doibot.html/doibot.php now run smoothly on testwiki. doibot.php has the capability to check the wikitext to be saved and POST the appropriate request to doibot.php to submit the checked page text.