navbarMenu horizontal dividers

[wch]

This closes #888.

Example app:

shinyApp(
  ui = navbarPage("App Title",
    tabPanel("Plot"),
    navbarMenu("More",
      tabPanel("Summary"),
      "----",
      "Header text",
      tabPanel("Table")
    )
  ),
  server = function(input, output) { }
)

[vnijs]

Just tried out the PR. Very nice! I did notice that it will also turn an id into a dropdown-header.

shinyApp(
  ui = navbarPage("App Title",
                  tabPanel("Plot"),
                  navbarMenu("More",
                             id = "Not a header",
                             tabPanel("Summary"),
                             "----",
                             "Header text",
                             tabPanel("Table")
                  )
  ),
  server = function(input, output) { }
)

[wch]

Thanks for finding that case! I think that with the previous code, the id argument would basically get thrown away -- it wouldn't actually be used.

I think probably the right thing to do is to make sure that all the tab items are unnamed arguments, though it's possible I'm overlooking something. If we don't add that check, it's probably also makes sense to just use the behavior that you found in this pull request, and have the id argument (and any others) be treated like other unnamed arguments to navbarMenu. The first option is probably better for the sake of correctness; the second option is better for backward compatibility.

[vnijs]

Does this mean that the id parameter can be removed from the function definition of navbarMenu?

[wch]

id isn't in there: https://github.com/rstudio/shiny/blob/8a721fb/R/bootstrap.R#L398

[vnijs]

Ah. I misread the diff on github. Thanks again for adding this feature!