External links in the Customizer preview should open in a new tab instead of failing silently

[celloexpressions]

Related: #32711. Any non-previewable link should be opened still, just in a new tab where it can be opened.

[designsimply]

This one's tough. I feel like some people will like non-previewable links opening in a new tab or window and other people would not. Thinking about the flow someone is in while customizing, I think opening a new tab and changing focus to it could be disruptive. At the same time, I think those links shouldn't be completely dead. Would you consider just adding a feedback notice and maybe force users to do something like cmd+click to open the non-previewable links. Once someone learns the cmd+click behavior, they would do that and skip the notice while people who want to stay in the customize flow would not have new tabs or windows opened unexpectedly. Just thoughts so far. I know it confuses people in practice when the links don't work but I'm not sure yet what the best solution for that is within the context of live previews. More opinions welcome.

[celloexpressions]

I'd rather have the link open automatically than get a notice that it can't be previewed. Since you can't always tell whether a link is previewable or not, this would allow you to always flow to the link you wanted, with the new tab indicating that it isn't previewable directly rather than flowing through a warning.

[celloexpressions]

Since we're not going to be looking at this until a future release anyway, additional ideas would be appreciated here. Currently we have:

• Open non-previewable links in a new tab automatically
• Show a notice when a user attempts to open a non-previewable link in the preview

[celloexpressions]

Just noticed today that you can't open a link in a new tab with ctrl+click - the only way to do it is by right-clicking. So we definitely need to do something here, since even default browser behavior doesn't work for users that know how to use it.

[westonruter]

Replying to celloexpressions:

• Show a notice when a user attempts to open a non-previewable link in the preview

I implemented this in my now-stale patch for transactions (#30937).

[westonruter]

I think this is invalid now. External links in the preview now have cursor:not-allowed with a11y speech communicating that as well. The one thing not done is a mobile/touch helps for links that cannot be previewed.