feat(popover): introduce disabled flag

[medinarkhov]

Fixes #2188

PR created as a continuation of PR #2217

[disabled] would be a useful feature for popover\toltip, allowing user to create conditional popover\tooltip.
<div [ngbPopover]="It can be conditionally hidden!" [disabled]="hidePopover"></div>

[medinarkhov]

@pkozlowski-opensource please review. If the change looks good then I will add another commit to update:

• tooltip to have [disabled] flag (remove conditional content then?)
• update API
• update demo

[maxokorokov]

We should find a better name, otherwise LGTM.

I think it's a better option, than not showing it for falsy values (of what? content? title?) and more user-friendly than using imperative API

Would have the same API for the tooltip

P.S. Also afterwards, please open separate PRs, not commits for the tooltip (it will be a breaking change I think) and demos updates.

[maxokorokov]

1. Don't think it will be acceptable, too many collisions, ex:

<button [disabled]="true" ngbPopover>...</button>

maybe [showPopover] or [disablePopover]?

<div [ngbPopover]="text" [showPopover]="text !== ''" />
<div [ngbPopover]="text" [disablePopover]="text === ''" />

Don't like [hidePopover], because it implies that popover is open at the first place

2. All other inputs initial values come from NgbPopoverConfig. I think we should put this one there as well. Not 100% sure though if there is a use case for massively initializing all popovers as disabled... So this is questionable

[medinarkhov]

@maxokorokov thank you for prompt review.

Update:

1. renamed [disabled] flag to [disablePopover]
2. updated popover-config.ts
3. won't touch Tooltip in this PR

API page looks good. Let me know if more changes required? Would you like demo example?

[maxokorokov]

LGTM except for one small comment, and let's wait for feedback from @pkozlowski-opensource, if he agrees to add this to public API

[maxokorokov]

You just forgot this.disablePopover = config.disablePopover in the constructor, and no need to initialize it here

[medinarkhov]

good catch! fixed)

[pkozlowski-opensource]

LGTM, thnx!