A possible indicator of whatever's going wrong: the visualeditor API parse call always returns Main_Page regardless of what was requested.

e.g. I created a page called Sandbox (not via VisualEditor because of T259685), and then tried to edit it with VisualEditor. The following API request was made: http://localhost:8080/api.php?action=visualeditor&format=jsonfm&paction=parse&page=Sandbox&uselang=en&formatversion=2&oldid=2

The response came back as a success, but the content field contained the appropriate values for Main_Page rather than for Sandbox.

Then, unrelated to it receiving the wrong page, the code looking for a revisionid in the response document does documentElement.getAttribute( 'about' ) to look for the revisionid there, and discovers that there's no about element. This is why it claims to have found revisionid 0.

It's possible that this is being an issue independent of the docker/sqlite setup due to some less-used codepaths -- this is the non-restbase route, which is why the parse call is happening. None of our production sites have this setup, so...

It's possible that this is being an issue independent of the docker/sqlite setup due to some less-used codepaths -- this is the non-restbase route, which is why the parse call is happening. None of our production sites have this setup, so...

That said, making an equivalent API request over on enwiki, the parse output does include the about attribute.

@kostajh suggested I downgrade the docker image to 0.3.0 (from 0.5.0), which stopped this error from occurring.

In T261390#6443505, @DLynch wrote:

@kostajh suggested I downgrade the docker image to 0.3.0 (from 0.5.0), which stopped this error from occurring.

This is tracked in T261051: MediaWiki Docker does not support rest.php