Unable to open a newly inserted accordion panel

[cpsievert]

This issue was introduced by Shiny.renderContent() becoming async (in rstudio/shiny#3904).

In hindsight, it's quite obviously a bad idea for Shiny.renderContent() to always be async since, with any insert-like operation, users are going to expect that the operation to have finished before the next line of R code happens. Here's an example of that:

app.R

remotes::install_github("rstudio/shiny")

library(bslib)
library(shiny)

ui <- page_fixed(
  accordion(
    id = "acc", multiple = TRUE,
    accordion_panel("A", "a"),
    accordion_panel("B", "b")
  )
)

server <- function(input, output) {
  
  observe({
    # Triggers a Shiny.renderContent()
    accordion_panel_insert(
      "acc", accordion_panel("C", "c")
    )
    # Relies on the content being rendered
    accordion_panel_open("acc", "C")
  })
  
}

shinyApp(ui, server)

Going forward, it seems like it'd be a lot better to revert changes made to srcts/src/shiny/render.ts (except for the awaits in renderContentAsync()).

[wch]

Changing Shiny.renderContent() back to sync is problematic because it won't work with shinylive on Chrome. (More info at rstudio/shiny#3929 (comment))

I think what we can do is:

• Change Shiny's InputBinding.receiveMessage so that it can be sync or async (similar to OutputBinding.renderValue)
• Change all the uses of Shiny.renderContent() in bslib to use await.

[github-actions]

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