See ramnathv/htmlwidgets#487 for reference and background. @jcheng5 @seanbirchall

Debugging shinylive

Since MessageChannel replaces traditional Shiny websocket (easily tracked in browser debugging tools) in shinylive/webR, debugging can be a little more difficult. I discovered

1. options(shiny.trace = TRUE) in the app will log to browser console which is helpful
2. manually hacking shinylive-inject-socket.txt around line[https://github.com/posit-dev/shinylive/blob/main/src/assets/shinylive-inject-socket.txt#L62] by adding if(event.value && event.value.data) {console.log(JSON.parse(event.value.data))} after shinylive::export() in shinylive-sw.js provides the full stream

Potential Partial Solution (at least locally for me in shinylive)

While this helps in my local testing, I want to stress that the issue still eventually will appear if viewer is not cleared after first render. Before I was not able to get any rendered df_viewer, but it sounds like in the original issue that df_viewer would appear.

Moving lines to the end of mod_df_viewer.R seems to partially resolve what appears to be an asynchrony issue that happens in the shinylive context. Oddly, when I added a line before the req (even a commented one) without changing the order of the code, then the problem also went away at least locally in a shinylive context.

Sean, if working correctly, you should be able to remove the manually added dependencies in lines.

Problem

The shiny::req(ide$environment_selected, input$index, input$rows, input$columns) in line leads to a null data message sent. Then htmlwidgets line fails since data.deps does not exist.