fix: clear single-selection dropdown on character(0) and ""

Prior to this change only multi-selection dropdown could be cleared.
This change makes `update_dropdown_input` behavior analogous to
`shiny::updateSelectInput`.

R/dropdown.R

@@ -149,7 +149,8 @@ selectInput <- function(inputId, label, choices, selected = NULL, multiple = FAL
 #' @param input_id The id of the input object
 #' @param choices All available options one can select from. If no need to update then leave as \code{NULL}
 #' @param choices_value What reactive value should be used for corresponding choice.
-#' @param value The initially selected value.
+#' @param value A value to update dropdown to. \code{character(0)} and \code{""} clear the dropdown.
+#' \code{NULL} (the default) does not change selection.
 #'
 #' @examples
 #' if (interactive()) {

inst/www/shiny-semantic-dropdown.js

@@ -32,6 +32,10 @@ $.extend(semanticDropdownBinding, {
 
   // Given the DOM element for the input, set the value.
   setValue: function(el, value) {
+    if (value === '') {
+      $(el).dropdown('clear');
+      return;
+    }
     if ($(el).hasClass('multiple')) {
       $(el).dropdown('clear', true);
       value.split(",").map(v => $(el).dropdown('set selected', v));