valueBox class not always being cleared

[davidski]

When setting the color attribute based upon the value of the input to valueBox when using the Shiny runtime, the valuebox div does not always have the previous class removed and winds up with two bg-* classes applied (and the wrong value taking precedence).

To reproduce:

1. Run the following example (or check out the live running version on Shinnyapps)
2. Choose danger and see the color change as expected
3. Choose success and see the color change as expected
4. Choose danger again and see the color not change. Inspecting the HTML shows two classes now applied.

Example code as follows:

---
title: "Shiny testbed"
output: 
  flexdashboard::flex_dashboard:
    orientation: columns
    vertical_layout: fill
runtime: shiny
---

```{r setup, include=FALSE}
library(flexdashboard)
library(tidyverse)

Column {data-width=650}

Chart A

data(mtcars)
ggplot(mtcars, aes(mpg, cyl)) + geom_point()

Column {data-width=350}

Input Selection

class_color <- c("warning", "danger", "success")
selectInput("input_value", "Choose Color", class_color)

Datatable

options(DT.fillContainer = FALSE)
options(DT.autoHideNavigation = FALSE)
DT::renderDataTable({
 dat <- mtcars
 DT::datatable(dat, options = list(
    scrollY = "200px"
  ))
})

Valuebox

renderValueBox({
  dat <- input$input_value
  valueBox(dat,
           caption = "Testing colors", icon = "fa-pencil", 
           color = dat)
})

[jjallaire]

I've seen this bug before but had hard time reproing it -- this drove me crazy! Thanks so much, I'll see if I can get it fixed based on your example.