[Labs] Only unique values in TagInput

[jacekjagiello]

Possibility to have only unique values in TagInput component.

Concerns:

• Should we support this out of the box? Maybe it's responsible of user code which controls values passed to TagInput component?
• Should we call some kind of method from props, when I'm trying to add value that already exists?
• Should we define uniqueness only base on value?

[giladgray]

@jacekjagiello I do not think this feature belongs in TagInput--it goes against the fully controlled nature of the API. Also, the code is simple enough (in your PR) that there's little value in including it directly in the component: it's just a single filter, and I'm sure that defining uniqueness based only on strict string equality will not be sufficient across the board.

Something that I thought about while developing this initial version was supporting a return value from onAdd to control the input-clearing behavior: return false to say "I don't want to add this," and the component will ignore the event and not clear the input. That alone would allow users to implement whatever sort of behavior they like. (Same thing for onRemove is less valuable cuz there's no behavior in the component--removing the item is user code responsibility.)

How does that sound, instead of this feature?

[jacekjagiello]

@giladgray Yeah, valid points. Supporting a return value definitely sound better. ;) Can you elaborate this feature more? I mean, for me it means something as simple as:

const onAddResult = Utils.safeInvoke(this.props.onAdd, value);
if (onAddResult !== false) {
    this.setState({ inputValue: "" });
}

When onAdd can return boolean | void. Is that all or I miss something?

Ps. Sorry for wrong issue number in commits. I referred this issue instead of 1220, but I've fixed commit names.

[llorca]

@jacekjagiello I agree with Gilad, let's keep the component fully controlled. Your little snippet for onAdd?: (value: string) => boolean | void seems good, would you like to try and open a PR for it? You could then add a "Unique values only" toggle to the example to showcase this upgraded onAdd callback 💯

[jacekjagiello]

@llorca Sure, can you close this issue and start a new one? Or do you want to keep this under current issue?

[llorca]

@jacekjagiello We can keep this issue open and close up the current PR 👍

[cmslewis]

@llorca @giladgray @jacekjagiello - I took a stab at this in #1309. Lemme know how that looks.