"No method asJSON S3 class: R6" error when running example

[shaunalambe5]

I tried replicating the example from ShinyConf (allowing LLM to update the front-end) but it returns an error - see attached. I followed the code from the demo and the python template online.

Code below:

library(ellmer)
library(shiny)
library(shinychat)
library(bslib)

ui <- bslib::page_sidebar(
  sliderInput("slider", label = "slider input", value = 50, min = 0, max = 100),
  sidebar = chat_ui("chat",
                    messages = "Welcome! Try asking me to <span class='suggestion'>update the slider to 80</span> "
  )
)

server <- function(input, output, session){
  
  update_slider <- function(value) {
    updateSliderInput(
      inputId = "slider",
      value = value
    )
  }
  
  chat <- chat_openai(
    model = "gpt-4o-mini",
    system_prompt = "You are a helpful assistant in the sidebar of a Shiny app.
        You have a tool available to you to update a slider in the main panel of the app."
  )
  
  update_slider |>
    tool(
      "Updates the slider input",
      value = type_integer()
    ) |>
    chat$register_tool()
  
  observeEvent(input$chat_user_input, {
    stream <- chat$stream_async(input$chat_user_input)
    chat_append("chat", stream)
  })
  
}

shinyApp(ui, server)

[gadenbuie]

Hi @shaunalambe5! It took me a bit to diagnose, but the error is happening because ellmer takes the return value of the tool and sends it back to the LLM. So instead of trying to send the return value of updateSliderInput() (which is somehow an R6 object that ellmer can't serialize), send a string back to the LLM saying that the action was taken:

  update_slider <- function(value) {
    updateSliderInput(
      inputId = "slider",
      value = value
    )
    "The value was updated."
  }

[gadenbuie]

I've confirmed that the app crashing will be resolved in shinychat v0.2.0 (see #44), but the error message is still quite opaque.

[shaunalambe5]

Hi @gadenbuie, thanks for getting back so quickly. Adding the return string fixed it for me :) Thank you!

[gadenbuie]

Great! Glad to hear that solved your problems!