jsonlite warning with shiny 1.4.0

[stla]

Hello,

Consider this app:

library(shiny)
library(ggplot2)

ui <- fluidPage(
  radioButtons("type", "Type of plot", choices = c("density", "boxplot")),
  plotOutput("plot")
)

server <- function(input, output){
  output[["plot"]] <- renderPlot({
    if(input$type == "density"){
      ggplot(iris, aes(Sepal.Length)) + geom_density()
    }else{
      ggplot(iris, aes(x = "", y = Sepal.Length)) + geom_boxplot()
    }
  })
}

shinyApp(ui, server)

When you select the radio button "boxplot", this message appears in the R console:

Input to asJSON(keep_vec_names=TRUE) is a named vector. In a future version of jsonlite, this option will not be supported, and named vectors will be translated into arrays instead of objects. If you want JSON object output, please use a named list instead. See ?toJSON.

It is caused by x = "" in the aes. If I remove this argument, there's no warning anymore.

This message didn't appear with shiny < 1.4.0.

[harrismcgehee]

Similar experience with any single x axis item:

library(shiny)
library(ggplot2)

ui <- fluidPage(
            tabsetPanel(
                tabPanel("no message", plotOutput("quietPlot")),
                tabPanel("generates `Input to asJSON` message", plotOutput("noisyPlot"))
            )
)

# Define server logic required to draw cols
server <- function(input, output, session) {
    output$quietPlot <- renderPlot({
        ggplot(
            data = data.frame(z = c("a", "b"), n = c(1, 2)),
            aes(x = z, y = n)
        ) + geom_col()
    })
    output$noisyPlot <- renderPlot({
        ggplot(
            data = data.frame(z = c("a"), n = c(1)),
            aes(x = z, y = n)
        ) + geom_col() 
    })
}

shinyApp(ui = ui, server = server)

[jntrcs]

Also receiving this warning whenever x-axis is reduced to single factor.

[kaijagahm]

I am getting this warning message when I use onRestore and onBookmark. When I run the same app without those functions, the warning disappears.

[wch]

@kaijagahm Can you file a new issue, with a minimal reproducible example?

For the others that have experienced this issue, when I run the example apps, I don't see the message. It's possible that it has been fixed since the issue was originally filed. If you still see that message, please provide the output of sessionInfo() or sessioninfo::session_info().

[SigurdJanson]

I am not sure this issue is limited to ggplot. I have the same warning whenver I the value argument is a named vector. The problem is there even in shiny 1.6 (session info below). Once I put unname() around it, it works.

I'd prefer if the update-function would just ignore the names in the vector.

library(shiny)

ui <- fluidPage(
    titlePanel("as JSON Warning Sample"),
    mainPanel(
       sliderInput("inpSlider", "Just another value", 1, 10, 5),
       actionButton("btnReset", "Reset to 1")
    )
)

server <- function(input, output, session) {
    observeEvent(
        input$btnReset, 
        {    # NAMED VECTOR CAUSES THE WARNING
             updateSliderInput(session, "inpSlider", value = c(a = 1)) 
        })
}

shinyApp(ui = ui, server = server)

> sessionInfo()
R version 4.0.3 (2020-10-10)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 10 x64 (build 19041)

Matrix products: default

locale:
[1] LC_COLLATE=German_Germany.1252  LC_CTYPE=German_Germany.1252   
[3] LC_MONETARY=German_Germany.1252 LC_NUMERIC=C                   
[5] LC_TIME=German_Germany.1252    

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] shiny_1.6.0

loaded via a namespace (and not attached):
 [1] Rcpp_1.0.6        withr_2.4.1       digest_0.6.27     later_1.1.0.1    
 [5] mime_0.9          R6_2.5.0          jsonlite_1.7.2    lifecycle_0.2.0  
 [9] xtable_1.8-4      magrittr_2.0.1    cachem_1.0.1      rlang_0.4.10     
[13] promises_1.1.1    jquerylib_0.1.3   bslib_0.2.4       ellipsis_0.3.1   
[17] tools_4.0.3       tinytex_0.29      rsconnect_0.8.16  httpuv_1.5.5     
[21] xfun_0.20         fastmap_1.1.0     compiler_4.0.3    htmltools_0.5.1.1
[25] sass_0.3.0   

[wch]

@SigurdJanson Thanks for that example. This is a difficult (or really, almost impossible) problem to fix in general, because of R's nature as a loosely-typed language.

The root issue is that jsonlite doesn't like named atomic vectors when keep_vec_names=TRUE:

> jsonlite::toJSON(c(a=1), keep_vec_names=TRUE)
Input to asJSON(keep_vec_names=TRUE) is a named vector. In a future version of jsonlite, this option will not be supported, and named vectors will be translated into arrays instead of objects. If you want JSON object output, please use a named list instead. See ?toJSON.
{"a":1} 

In contrast, named lists are fine:

> jsonlite::toJSON(list(a=1), keep_vec_names = TRUE)
{"a":[1]} 

In the examples posted previously, it seems that something in ggplot2 generated data with named atomic vectors. In @SigurdJanson's example, it's the call to updateSliderInput() that tries to send a named vector.

In Shiny, we do some input validation, we don't check every possible input for every possible kind of invalid value. (It's similar to the vast majority of R code in this way.) With a strongly-typed language, many checks just happen automatically; with a loosely-typed language like R, deciding which things to check (and whether to "fix" them for the user) is much more subjective.