I don't think this should be considered part of T40638. The problem is not that the message needs rewording; the problem is that the actual error message is not shown.

MobileFrontend needs to show the actual error returned by the API when the edit fails, rather than try to handle all possible cases by itself, since the error message may even be "dynamically" defined on the wiki (for edits prevented by an abuse filter or title blacklist).

Our team isn't focused on changes to Wikitext Editor at this time.

Somewhat related: in T229532 we're changing VE to also use the errors from the API (rather than our custom handling in some cases), which should help validate this approach.

In T2T228897, @Huon wrote:

I can't tell what caused the error

This error message is shown when internet connectivity is lost between the time of previewing and publishing.

Yes, I've noticed it as well. For example, editing Cascade protected files and pages. If I try to edit a Cascade protected page and save it, it gives an error message that the edit could not be saved.

Steps to reproduce

• Go to English Wikipedia main page.
• Now click on a image, transcluded in the page.
• If the image is in Wikimedia Commons, there will be a warning in the file page "This page is editable only by administrators because it was transcluded in a Cascade protected page.
• Now, you'll notice that there is still a edit button present in the page even if you are not an administrator.
• Then edit the page and try to save it.

Expected result

• It gives a described warning why the edit couldn't be saved.

Actual result

• It just says "Your edit could not be saved." without any explanation why it could not be saved whatsoever.

Change 537223 had a related patch set uploaded (by Bartosz Dziewoński; owner: Bartosz Dziewoński):
[mediawiki/extensions/MobileFrontend@master] mobile.editor.overlay: Use errorformat=html and display all error messages

https://gerrit.wikimedia.org/r/537223

I have not yet thoroughly tested the patch, there's a long list of cases to check (my experience when implementing a similar change in VE: T229532#5430000). But just to give a representative example, here's the before-and-after for the scenario with cascading protection:

Before	After

Also, for this particular case, of course the editor would ideally display a warning before you waste your time editing; that's a separate problem and filed as T219848.

Change 537223 merged by jenkins-bot:
[mediawiki/extensions/MobileFrontend@master] mobile.editor.overlay: Use errorformat=html and display all error messages

https://gerrit.wikimedia.org/r/537223

This can be tested using storybook by working through the editor until you hit save - where you'll see the error.

https://doc.wikimedia.org/MobileFrontend/master/js/ui/?path=/story/editor--sourceeditoroverlay-abusefilter-spam
https://doc.wikimedia.org/MobileFrontend/master/js/ui/?path=/story/editor--sourceeditoroverlay-edit-conflict
etc..