fix(renderPlot): get interactive plotting working with ggplot2 v4.0

[cpsievert]

This update gets renderPlot() interactive ggplot2 feature working with ggplot2's upcoming transition from S3 to S7 (tidyverse/ggplot2#6364).

Note that #4226 fixed a similar issue, but only for our unit tests. The same problem exists in renderPlot()'s interactive feature, which we don't have any automated tests for.

For a minimal example, with this app, no brushed points are returned when brushing the plot.

library(shiny)
library(ggplot2)
library(bslib)

ui <- page_fixed(
    card(
    card_header("Interactive Brushing Plot"),
    plotOutput("plot", brush = "plot_brush"),
    card_footer("Drag to select points on the plot")
  ),
  card(
    card_header("Selected Data Points"),
    tableOutput("brushed_data")
  )
)

server <- function(input, output, session) {
  
  output$plot <- renderPlot({
    ggplot(iris, aes(x = Sepal.Length, y = Sepal.Width, color = Species)) +
      geom_point(size = 3) +
      theme_minimal()
  })
  
  output$brushed_data <- renderTable({
    req(input$plot_brush)
    
    brushed_data <- brushedPoints(
      iris, input$plot_brush, 
      xvar = "Sepal.Length", yvar = "Sepal.Width"
    )
    
    if(nrow(brushed_data) == 0) {
      return(data.frame(Message = "No points selected"))
    }
    
    brushed_data
  })
}

shinyApp(ui = ui, server = server)

With this change, you'll get the expected behavior:

Testing notes

• First, verify the example above is broken by installing the new ggplot2 remotes::install_github("tidyverse/ggplot2#6364")
• Next, install this change, and verify the problem is fixed: remotes::install_github("rstudio/shiny#4228")

More generally, we should do more testing of shiny's interactive ggplot2 plot feature to make sure there isn't more changes that we're missing. We still have a handful of apps that we designed for manually testing, but never got automated tests:

093-plot-interaction-basic
094-image-interaction-basic
095-plot-interaction-advanced
096-plot-interaction-article-1
097-plot-interaction-article-2
098-plot-interaction-article-3
099-plot-interaction-article-4
100-plot-interaction-article-5
101-plot-interaction-article-6
102-plot-interaction-article-7
103-plot-interaction-article-8
104-plot-interaction-select
105-plot-interaction-zoom
106-plot-interaction-exclude

It'd also be great to verify that these apps are working as intended with the latest ggplot2 (plus this change). Testing across different environments isn't that important (we're just looking for changes in ggplot2's R code that we're not accounting for).

[karangattu]

The tests across all listed apps showed no issues with the ggplot2 plotting functionality in this branch of Shiny.