MediaWiki version: 1.31.1
VisualEditor version: 0.1.0 (rEVED13a585a7ec0d)

Steps to reproduce:

• Set up a foreign file repo with the following:

	$wgForeignFileRepos[] = [
		'class' => ForeignAPIRepo::class,
		'name' => 'somename',
		'apibase' => 'https://mysite.com/w/api.php',
		'url' => '/wiki/images',
	];

• Upload a file called DeepPlane.jpg there
• Search for DeepPlane in VisualEditor
• Nothing shows up

What seems to happen is that only full word matches are returned, but the file extension is taken into account in the 'word'. For example a search for DeepPlane.jpg does return the file, while DeepPlane does not. The search behaviour seems rather close to splitting the file name by spaces/underscores or dashes and looking for exact matches in either of the words.

A file named Hello_There.jpg will show up when searching for Hello, but not for There. It will however show for There.jpg.

Hope I explained this clearly.