Fix updateDateRangeInput when only one of start/end updated

[gaborcsardi]

App to test:

shinyApp(
  ui = fluidPage(
    div(
      dateRangeInput("daterange", "Date range:",
                     start = "2001-01-01",
                     end   = "2010-12-31")
    ),
    actionButton("btn1", "leave start & end alone"),
    actionButton("btn2", "set date range start"),
    actionButton("btn3", "set date range end"),
    actionButton("btn4", "set date range start and end")
  ),
  server = function(input, output, session) {
    observeEvent(input$btn1, updateDateRangeInput(session, "daterange"))
    observeEvent(input$btn2, updateDateRangeInput(session, "daterange", start = "2005-01-01"))    
    observeEvent(input$btn3, updateDateRangeInput(session, "daterange", end = "2006-01-01"))
    observeEvent(input$btn4, updateDateRangeInput(session, "daterange", start = "2007-01-01", end = "2008-01-01"))
  }
)

[wch]

I think this isn't quite right. When click the middle two buttons, it sets one value, but blanks out the other. Isn't that supposed to happen only when the value is NA?

[gaborcsardi]

Hmmm. Interesting. I tested it before the other PR was merged, will test it again in a sec.

[gaborcsardi]

It looks like the R list(NULL, NULL) is converted to [null, null] in JS, just like list(NA, NA).
:( This was not a problem before the other PR, because null values were ignored....

E.g. see the first two buttons.

shinyApp(
  ui = fluidPage(
    div(
      dateRangeInput("daterange", "Date range:",
                     start = "2001-01-01",
                     end   = "2010-12-31")
    ),
    actionButton("btn1", "leave start & end alone"),
    actionButton("btn11", "reset start & end with NA"),
    actionButton("btn2", "set date range start"),
    actionButton("btn3", "set date range end"),
    actionButton("btn4", "set date range start and end")
  ),
  server = function(input, output, session) {
    observeEvent(input$btn1, updateDateRangeInput(session, "daterange"))
    observeEvent(input$btn11, updateDateRangeInput(session, "daterange", start = NA, end = NA))
    observeEvent(input$btn2, updateDateRangeInput(session, "daterange", start = "2005-01-01"))    
    observeEvent(input$btn3, updateDateRangeInput(session, "daterange", end = "2006-01-01"))
    observeEvent(input$btn4, updateDateRangeInput(session, "daterange", start = "2007-01-01", end = "2008-01-01"))
  }
)

How about passing a named list to JS? That should solve this I think.

[wch]

A named list sounds good idea.

[gaborcsardi]

See #1317. A named list is passed now, but NULL values are dropped from it, so they have to effect.