Make sidebar-toggle bars icon work on Shiny 1.2 with FontAwesome 5

[alandipert]

Fixes #297 in a backward-compatible way. I tested using Shiny 1.1 from CRAN and the Shiny v1.2-rc branch on github.

Testing Notes

Testing old Shiny

1. Install Shiny from CRAN: install.packages("shiny")
2. Install shinydashboard from GitHub: devtools::install_github("rstudio/shinydashboard")

Run this example app:

library(shiny)
library(shinydashboard)

ui <- dashboardPage(
  dashboardHeader(),
  dashboardSidebar(),
  dashboardBody()
)

server <- function(input, output) { }

shinyApp(ui, server)

You should see the bars icon:

Testing new Shiny

1. Install Shiny from GitHub: devtools::install_github("rstudio/shiny@v1.2-rc")

Run the example app and confirm that you still see the bars icon.

[wch]

After this is merged, we should release a new version of shinydashboard, before shiny 1.2 is out.

Unfortunately, I think some people will see the icon problem. If they do install.packages('shiny') after shiny 1.2 comes out, but don’t also upgrade shinydashboard, then they'll see the problem. When we announce the new version of Shiny, we should also mention that they should upgrade shinydashboard.