feat: Add input_submit_textarea() input element

[cpsievert]

Adds input_submit_textarea(), a new input control that's akin to shiny::textAreaInput(), but delays the sending of an input value until a corresponding button is pressed.

Here is a hello world example:

library(shiny)
library(bslib)

ui <- page_sidebar(
  title = "Hello input_submit_textarea()",
  input_submit_textarea("text", placeholder = "Enter input to submit"),
  textOutput("value")
)

server <- function(input, output, session) {
  output$value <- renderText({
    Sys.sleep(1)
    paste("You entered:", input$text)
  })
}

shinyApp(ui, server)

TODO

• Tests
• Port to PyShiny
• Docs (component gallery)?

[cpsievert]

@gadenbuie ready for another review pass when you are

[gadenbuie]

I'm going to pull changes locally to poke around, but two things jumped out at me from the web view

[gadenbuie]

I have reservations about passing unnamed arguments from ... into the area next to the button.

For now, I'd rather we only accept named attributes and add them to the text area.

In general, I think this is a place where we shouldn't rely on ... and should have an argument that takes the UI elements that would go into the tray, or tool bar or whatever we end up calling it. I think that not allowing children in ... would give us some space to release bslib with input_submit_textarea() and figure out that API in the future.

My core objection is that I think we should be extremely reluctant to separate the destination of named and unnamed arguments in .... I think some separation is inevitable when it makes sense for attributes to be applied at a higher level in the DOM than where children are inserted, but they still need to be conceptually related to each other (things going into the sidebar, for example).

In this case, where attributes go to <textarea> and children go into some other location, it seems too far away to me. Having an argument for the children destination makes the final solution more readable and understandable because it'll be clear where children end up by the name of the argument.

[cpsievert]

Good point. I had briefly considered this, but hesitated on committing to name. Anyway, done in 7ccf8e8

[gadenbuie]

One final bit of polish: Currently, you have to click directly on the <textarea> input to give it focus, but it's easy to click on whitespace that's part of the container, thinking that you'll be clicking into the text area. I think it'd be best if any click inside the .bslib-input-submit-textarea component that isn't on the submit button would move focus to the text area.