related: T138499 (silent fail after just adding a reference but not putting anything in)

Having a disabled save button but no explanation why is bad. Fully agree. But enabling it and "tricking" the user into clicking a dysfunctional button, just to show an error message, is worse I feel. Same for saving dysfunctional values nobody else can later use or fix, because nobody else knows what the original user meant. That's what Wikidata is about after all, knowing what was meant.

Introducing a per-user "draft" concept into the Wikibase software is a fascinating idea we should continue to talk about. I suggest to find a better place to discuss this.

Alternative suggestions:

• Show the selector popup with a "nothing found" message.
• Do a wider "did you meant?" search when nothing is found, so the selector always shows at least one item to pick from.

Good points.

But enabling it and "tricking" the user into clicking a dysfunctional button, just to show an error message, is worse I feel.

It would at least show the information the user needs to carry on. I suggested this because it matches the behavior when URLs are saved. In general, I would much prefer a validation that shows it right away that there is a problem and how to fix it.

Same for saving dysfunctional values nobody else can later use or fix

Yes… I'm torn. I really like the Wiki concept of having "dysfunctional" links, but, indeed, I have no idea how an equally working thing would look and behave like on wikidata.

Show the selector popup with a "nothing found" message.

Yes – that is a good idea. I suppose, what makes it confusing that I can fill the field with letters that don't resolve to something and that they silently stay there after it is clear that they don't match – for the user it looks like "I entered [useful] information.

I try to mock up that.

Agree. Though we should keep in mind T138748 to have a solid, and maintainable structure for error message handling.

@Jan_Dittrich, I believe this is mostly solved with the addition of the "No match was found" message as well as T170531: Semantics: Make recognized property and value look different than unrecognized input. Feel free to reopen if you disagree.