Gerrit change 133955 https://gerrit.wikimedia.org/r/#/c/133955/, which I plan to merge on Thursday for deployment to WMF wikis with 1.24wmf7https://www.mediawiki.org/wiki/MediaWiki_1.24/Roadmap, will cause the API to report an error when action=edit is used with the "redirect" parameter and none of "appendtext", "prependtext", or "section=new" are used. This will occur regardless of whether the page being edited is actually a redirect.

API action=edit has a "redirect" parameter, which will automatically edit the target page if the supplied title is a redirect. The original intention of this feature was to be used in combination with appendtext or section=new for posting notifications to user talk pages without having to first check whether the page is a redirect (see bug 24330https://bugzilla.wikimedia.org/show_bug.cgi?id=24330). But as currently implemented it will perform the edit even when replacement page text is supplied, which is extremely prone to error: while reviewing the patch proposing this change, I reviewed several scripts and bots that were logged as submitting API requests with this combination of parameters and every one would make erroneous edits when the target page is a redirect.

Clients not using the "redirect" parameter to action=edit or clients that use it in combination with "appendtext", "prependtext", or "section=new" will not be affected by this change. Affected clients have several options for coping with this change, such as:

- Stop supplying the "redirect" parameter to action=edit, which will edit the redirect page itself. - When fetching the page content to transform it for the edit, use the "redirect" parameter to action=query and submit the edit to the target page directly (and without using the "redirect" parameter to action=edit) rather than via the redirect title. - Use appendtext, prependtext, or section=new instead of loading the page's wikitext and appending or prepending content on the client side. - Detect the redirect when fetching the page content and treat the unexpected redirect as an error condition. Or handle the error returned by action=edit in whatever manner is appropriate to your script, bot, or tool.

See https://www.mediawiki.org/wiki/MediaWiki_1.24/Roadmap for the deployment schedule.