Various improvements to tab panels (rstudio#3315)

* 'Native' Bootstrap 4 tabset panel support

* downgrade error to warning; improve the messaging

* Make tab anchor selectors more a bit more sensible and consistent across versions

* More of the same

* fix silly bug

* Be more careful about unpacking a .nav-item into a .dropdown-item

* Keep refactoring R logic to make it cleaner and easier to reuse elsewhere

* Go back to the purely class based CSS selectors for BS4 tab input

* Keep supporting off-label behavior of shiny.tag getting transformed into 'empty' nav/tab

* Add header and footer args to tabsetPanel()/navlistPanel() since there is precedence in navbarPage() and mention them in the warning

* Drop NULLs instead of creating an empty nav from them, closes rstudio#1928

* Remove tabPanelMenu() alias

* Add a card argument for wrapping content in a card

* Throw an error if card=T is used outside of a BS4+ context

* No more tabPanelMenu() alias

* Document (GitHub Actions)

* Port JS changes to TypeScript

* Allow liTag to be assigned a new value

* abort() is no longer being used

* Add some unit tests

* Document the new card argument

* Get tests passing on older R versions

* Get tests passing on older R versions

* Get tests passing on older R versions

* Skip snapshots on R < 3.6

* require dev version of htmltools

* remove card argument (at least for now)

* Document (GitHub Actions)

* Update tests/testthat/test-tabPanel.R

Co-authored-by: Winston Chang <[email protected]>

* Have processDeps() call renderTags() on tagFunction() objects

Co-authored-by: cpsievert <[email protected]>
Co-authored-by: Winston Chang <[email protected]>

NAMESPACE

@@ -408,6 +408,7 @@ importFrom(rlang,is_false)
 importFrom(rlang,is_missing)
 importFrom(rlang,is_na)
 importFrom(rlang,is_quosure)
+importFrom(rlang,list2)
 importFrom(rlang,maybe_missing)
 importFrom(rlang,missing_arg)
 importFrom(rlang,new_function)