There was recently a brief discussion on the enwiki technical village pump about the following issue, where Tim Starling suggested this should be fixed in the API [1]. I want to mention it here before filing a bug.
It's already known among the developers that there can be obsolete entries in the page table. One of these at the moment is pageid 414115 on enwiki, the article [[/.]], which has an illegal title. Unsurprisingly, when that page was last edited, it was a redirect to [[Slashdot]].
If I fetch the list of backlinks to [[Slashdot]] using the API, I get that page among the results. If I then try to fetch the page content for it (using action=query and prop=revisions) the API returns a bad title error ('invalidtitle'). This is of course a bad situation for people using the API.
Strangely, I can get the content of that page using a generator query [2].
- Carl
1. http://en.wikipedia.org/w/index.php?title=Wikipedia:Village_pump_%28technica...
2. http://en.wikipedia.org/w/api.php?action=query&generator=backlinks&g... The parameters are: ( 'action' => 'query', 'generator' => 'backlinks', 'titles' => 'Slashdot', 'gblfilterredir'=> 'redirects', 'prop' => 'revisions', 'rvprop' => 'ids|user|comment|content' );