help for renderCachedPlot gives bad advice for specifying height/width

[brooksambrose]

shiny::renderCachedPlot throws "formal argument matched by multiple actual arguments" error when specifying height or width. The help page says that dots are passed to grDevices::png:

... Arguments to be passed through to png. These can be used to set the width, height, background color, etc.

In fact the dots are passed to shiny:::DrawPlot where height and width are specified from the sizePolicy argument. Thus following the docs as written leads to an error. While I expect the code represents the intended behavior, I would suggest improving the docs to explain that height or width cannot be specified in the same way as renderPlot, and possibly building in a warning that issues guidance about fixing the problem. To reproduce the behavior of renderPlot one must set sizePolicy with a growth rate of 1, e.g. sizeGrowthRatio(width = 400, height = 400, growthRate = 1).

library(shiny)

ui <- fluidPage(
  titlePanel("Hello Shiny!"),
    mainPanel(
      plotOutput(outputId = "renderPlot")
      ,plotOutput(outputId = "renderCachedPlot")
      ,plotOutput(outputId = "renderPlot_hw")
      ,plotOutput(outputId = "renderCachedPlot_hw")
      ,plotOutput(outputId = 'renderCachedPlot_sizePolicy')
    )
  )

server <- function(input, output) {
  output$renderPlot <- renderPlot({
    hist(faithful$waiting, main = "renderPlot, height/width default")
    })
  output$renderCachedPlot <- renderCachedPlot({
    hist(faithful$waiting, main = "renderCachedPlot, height/width default")
    },cacheKeyExpr = '')
  output$renderPlot_hw <- renderPlot({
    hist(faithful$waiting, main = "renderPlot, height/width 400")
    },height=400,width=400)
  output$renderCachedPlot_hw <- renderCachedPlot({
    hist(faithful$waiting, main = "renderCachedPlot, height/width 400")
    },cacheKeyExpr = '',height=400,width=400)
  output$renderCachedPlot_sizePolicy <- renderCachedPlot({
    hist(faithful$waiting, main = "renderCachedPlot, height/width 400")
    },cacheKeyExpr = '',sizePolicy = sizeGrowthRatio(width = 400, height = 400, growthRate = 1))
}
shinyApp(ui = ui, server = server)
#> 
#> Listening on http://127.0.0.1:7185
#> Warning: Error in drawPlot: formal argument "width" matched by multiple actual
#> arguments
#> Warning in log(x/base, rate): NaNs produced

#> Warning in log(x/base, rate): NaNs produced

^{Created on 2020-07-27 by the reprex package (v0.3.0)}

[akshat-max]

Hey I am new to open source and really want to get kick start to it can you assign me this issue if it's open.