This issue is in echo with issues #231, #227, #241, #294, #329, #363, #421, #470, #473 and maybe some others...

The need to update the version of mermaid.js embedded in the DiagrammeR package is pressing.

As suggested in #421, we can manually update the file /DiagrammeR/htmlwidgets/lib/mermaid/dist/mermaid.slim.min.js in the installation folder of the package with the last version downloaded from https://cdn.jsdelivr.net/npm/mermaid/dist/mermaid.min.js.

One way to always have the latest version of DiagrammeR in the package could be to add an updateMermaid function in the package:

#'  Update the mermaid library in the package
#' @param version A [character] of the desired version (the latest by default)
#' @return See value returned by [download.file]
updateMermaid <- function(version = "") {
  url <- "https://cdn.jsdelivr.net/npm/mermaid@version/dist/mermaid.min.js"
  if (version != "") {
    stopifnot(grepl("^[[:digit:]]+\\.[[:digit:]]+\\.[[:digit:]]+$", version))
    version <- paste0("@", version)
  }
  url <- gsub("@version", version, url)
  try(
    download.file(url, 
                  system.file("htmlwidgets/lib/mermaid/dist/mermaid.slim.min.js", 
                              package = "DiagrammeR"))
  )
}

There are several issues with this solution:

• this url could not be the best one to use to get an up to date and persistent reference for downloading the mermaid.js library
• I don't know if the CRAN authorises to modify the content of the library by itself. But I don't know where to locate the mermaid.js library file elsewhere

@rich-iannone what do you think of that?