Sooooo...

As a matter of principle on *WMF* wikis, I agree, this would be a useful change. *However*, I think it's worth noting that it's totally valid to create files without file extensions, and therefore, it should not *necessarily* be forbidden. I would much rather see us interpret the empty string ("") in the "allowed file extensions" configuration array as a "no extension" option, and disallow upload of no-extension files (ending in . or not having a period) if that is not present.

That said, those filetypes should almost definitely be interpreted as potentially dangerous.

As for creating a page in the file namespace, I may lack some context, but why is that even allowed without an upload? Is there some prevalent Commons cultural practice involving ritual altars and horn-shaped candles that I'm not aware of that also requires non-file File pages? Maybe we can just restrict or remove that possibility. On the other hand, we could also require that any file pages match the allowed file extensions.

In T153864#2896455, @MarkTraceur wrote:

As for creating a page in the file namespace, I may lack some context, but why is that even allowed without an upload? Is there some prevalent Commons cultural practice involving ritual altars and horn-shaped candles that I'm not aware of that also requires non-file File pages? Maybe we can just restrict or remove that possibility. On the other hand, we could also require that any file pages match the allowed file extensions.

I wouldn't rule out ritual altars, but at the very least it's possible to create redirects this way.

{{prohibited name}} is used that way on Commons.

Change 337854 had a related patch set uploaded (by Matthias Mullie):
Disallow wikitext creation of invalid filenames in NS_FILE

https://gerrit.wikimedia.org/r/337854

If we were to flat out disallow creation of all NS_FILE titles that would be invalid filenames, would that affect too much? In other words: are there valid cases where we would like to support NS_FILE titles that are not valid filenames?

It is occasionally useful to create redirects under invalid filenames, when a file is linked to incorrectly in some external content. I don't have an example handy, but I could dig some up if you need.

Here you are:

https://commons.wikimedia.org/w/index.php?title=File:2010-02-19_16500x2000_chicago&redirect=no

(via https://quarry.wmflabs.org/query/16401)

This redirect was explicitly created to avoid to break a published URL, see https://en.wikipedia.org/wiki/File_talk:2010-02-19_16500x2000_chicago

FWIW, there are a lot of overlay.kml subpages of existing file pages. They aren't exactly extensionless, but I imagine they would fall under "invalid filenames" criteria.

There was talk in the past about decoupling raw filenames from titles in the file: namespace so that extensions aren't exposed on new uploads, titles can contain funky chars, and file types can be upgraded without breaking usage.

cf T6421, T25255

I'll abandon my patch here. There's little reason to disallow creating extensionless titles, if we plan to make files extensionless at some point.

Change 337854 abandoned by Matthias Mullie:
Disallow wikitext creation of invalid filenames in NS_FILE

Reason:
No longer makes sense (see phab)

https://gerrit.wikimedia.org/r/337854