HTML documents including plotly plots are not reproducible

I believe it is known that the value of plotly::plot_ly(x = 1, y = 1)$x$cur_data is hard to reproduce, compare https://github.com/plotly/plotly.R/issues/1048. Some work has been done in #1379 towards use in shinytest at least.

I am also using shinytest, but in my app, users are downloading HTML files with plotly plots generated using rmarkdown::render(). So these files are still non-reproducible because I cannot seem to use renderPlotly() inside rmarkdown::render(). To see the problem:

bug.Rmd:

---
output: html_document
---

```{r}
plotly::plot_ly(x = 1, y = 1)
```

Then run R -q -s -e 'rmarkdown::render("bug.Rmd")' and see the value of cur_data in bug.html change every time you regenerate it.

I see two options:

• I could replicate the logic of
  https://github.com/plotly/plotly.R/blob/bab01af316673e35d8314129178bfb27eed27fe7/R/shiny.R#L46-L53
  inside bug.Rmd, like this:

  p <- plotly::plot_ly(x = 1, y = 1)
  p$x$attrs <- NULL # and a few more
  p
  

  However, this breaks the plot. Any way I can make this work?
• I have also tried putting this inside bug.Rmd:

  shiny::snapshotPreprocessOutput(
    plotly::plot_ly(x = 1, y = 1),
    function(value) {
      # https://github.com/plotly/plotly.R/blob/3d49fbc5897703d58b/R/shiny.R#L68
      json <- jsonlite::from_JSON(value)
      json$x <- json$x[setdiff(names(json$x), c("visdat", "cur_data", "attrs"))]
      # https://github.com/plotly/plotly.R/blob/3d49fbc589/R/utils.R#L1020-L1025
      jsonlite::toJSON(json,
        digits = 50, auto_unbox = TRUE, force = TRUE,
        null = "null", na = "null", time_format = "%Y-%m-%d %H:%M:%OS6"
      )
    }
  )
  

  but rmarkdown::render() seemed to ignore it, even inside shinytest (or did I do anything wrong there)?
• One could amend #1365 to take into account a hash of the current plot serialization to avoid generating identical IDs even if the external seed is reset to the same values externally. This would avoid the need for tempfile().

Reproduce the issue with bug.Rmd and R -q -s -e 'rmarkdown::render("bug.Rmd")', then compare the cur_data value in bug.html across renders. Read the referenced logic in R/shiny.R and R/utils.R, along with the related issues #1048, #1379, and #1365. Done means HTML documents rendered with rmarkdown::render() produce reproducible plot data without breaking the plot.