Actualy when someone try to transfer files from local to Commons using FileImporter it redirect to a error banner. Is it possible to completely disable FileImporter button in unfree files?
Topic on Help talk:Extension:FileImporter
I’m not sure that would result in better user experience. Now the user loads a page, just to get the message that the file cannot be transferred, which wastes several seconds. If the tab is removed, the user only sees that the tab is not there, without any explanation of why (and there are many possible reasons: lack of free license template, presence of {{Do not move to Commons}} or similar, hidden file revision etc.).
We investigated this at length as part of phab:T228858. There are two main reason we can not and do not want to do this: 1. Just disabling the buttons means users who see the button have no idea why it is disabled. Users need to be able to click it to see a helpful error message that allows them to understand what's going on. 2. Disabling the button means we would need to transfer all information from the Importer to the Exporter. This is technically so complicated, we believe it's not worth it.
I can understand that for a huge comunities, like english wiki, it can be usefull because there's a lot of newbies every day, and some of them probably will use this feature one day. But in a medium/small comunities like ukrainian wiki there's only a few users that use this feature and most of them (if not all) are experienced users, like me, and the presence of a useless button is very unconfortable for me, especially because i using a lot of other tools and feature to working with unfree files. My request is a possibility to disable locally this button in MediaWiki namespace (for all comunity) or just for me (via personal script).
Can you explain in more detail why the button makes you feel "uncomfortable"? There are many more buttons you probably never use. What's the specific issue with this one? Maybe it helps if you share a screenshot of your modified skin?
For what we at Wikimedia Deutschland do it's very important to always consider newcomers as well. It would be unhealthy, if not immoral to assume that all users in a particular community are experts. If we would do this, we would actively exclude newcomers – from communities that desperately need newcomers.
If the goal is to disable it with a user script (or an on-wiki gadget), creating an API on Commons (i.e. in FileImporter) could resolve it with no additional runtime cost compared to a FileExporter API (a script/gadget makes an API query anyway, it doesn’t matter whether it’s a local or a Commons one). That’s relatively cheap in terms of development and maintenance costs, and the script/gadget is opt-in by nature, so newbies don’t get it by default.
Yes, that's a possible implementation. However, having to provide long-term support and maintenance for an API is not cheap.