Mention plugin should allow autocomplete with space

[mateuszzagorski]

📝 Provide a description of the new feature

Currently, when you press spacebar while using the mention feature it will hide the dropdown and add space after what has been written - this is behaving exactly like mentions on GitHub.

However, it could be a more natural user experience if it would be working in a different way - where you can add space after for example @Barney (following the example from editor 2 - on features/mention page in docs) and still be able to filter the feed to select Barney Stinson from the dropdown.

This issue was already discussed partially here: #7306 - but that issue was created to resolve a slightly different problem, so I'm extracting this as a separate one.

Mentioning @EricPaulson and @robjbrain as you gave the most recent feedback regarding this and might want to leave a 👍 reaction.

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[CatStrategist]

Issue fixed in #11017

Mention plugin didn't allow spaces because of regexp for matching mentions in currently edited text that only allowed visible characters to occur after a mention mark.
At first it seemed as an easy improvement of regexp to just allow a space but a scenario with multiple registered markes complicated it a lot.

Take this case:

aaa @fooo #bar

Regexp allowing space would match @foo as well as #bar. After playing a little bit with regexp to handle that case it quickly got overcomplicated and still had some other edge cases so I had to withdraw from this approach.

Previously regexp to match mention tested entire text node till caret but what we really needed to test is just a text since last valid marker in text. But yet again, case with multiple markers complicated it a little bit. Previously there was a TextWatcher for each marker that tried to match a mention for it's own marker. It run outside of state of mention plugin and executed matched or unmachted events without knowledge of matches for other markers. It could find a match for one marker and tried to show UI, but the other marker fired unmatched event and immediately hid UI. Before going with solution for spaces it had to be fixed. When initializing plugin I've merged watchers to a single one who knows about each marker and runs only one on each text change. Having that in place, I could pass a test function to TextWatcher and find last valid marker in text, trim text since last marker (+1 a character behind to test if marker is in correct place) till caret. Having only that part the rest of the code could stay as usual with just a little change to regexp that now allows any character after marker character instead of just visible characters.

[robjbrain]

It seems like we're very restricted by the current implementation of the UI.

Would it be better to have an alternative plugin that when typing @ a popup appears with an input and the focus then goes on the input, something similar to the link UI.

This is what it looks like currently:

It could instead look something like this:

In this example Enter or Esc or using the green and red buttons would close the popup.

Such a plugin could be generic for multiple uses, such as such as # creating a popup of tags where you could search existing tags or create a new one. But could also be used for more advanced mentions that the basic mentions plugin itself can't cater for.

[Reinmar]

Hi @robjbrain! Thanks for the suggestion. However, this issue is solely about handling mentions with spaces and a quick win we can have there. Your idea goes well beyond this and would need a separate ticket.