R/visual-diff.R

In diffviewer: HTML Widget to Show File Differences

#' HTML widget to visually compare two files
#'
#' Currently supports:
#' * image diffs for `.svg` and `.png`
#' * tabular diffs for `.csv`
#' * text diffs for everything else
#'
#' @param file_old,file_new Paths to files to compare
#' @param width,height Output size
#' @seealso [visual_diff_output()] for use within Shiny apps
#' @returns A HTML widget
#' @export
#' @examples
#' path1 <- tempfile()
#' path2 <- tempfile()
#' writeLines(letters, path1)
#' writeLines(letters[-13], path2)
#'
#' if (interactive()) {
#'   visual_diff(path1, path2)
#' }
visual_diff <- function(file_old, file_new, width = NULL, height = NULL) {
  stopifnot(file.exists(file_old), file.exists(file_new))
  stopifnot(tolower(tools::file_ext(file_old)) == tolower(tools::file_ext(file_new)))

  widget_data <- list(
    old = file_data(file_old),
    new = file_data(file_new),
    filename = basename(file_old),
    typediff = file_type(file_old)
  )

  htmlwidgets::createWidget(
    name = "visual_diff",
    widget_data,
    width = width,
    height = height,
    package = "diffviewer"
  )
}

#' Shiny bindings for `visual_diff()`
#'
#' Use `visual_diff_output()` in ui and `render_visual_diff(visual_diff(...))`
#' in the server function.
#'
#' @param outputId output variable to read from
#' @param width,height Must be a valid CSS unit (like \code{'100\%'},
#'   \code{'400px'}, \code{'auto'}) or a number, which will be coerced to a
#'   string and have \code{'px'} appended.
#' @param expr An expression that generates a visual_diff
#' @param env The environment in which to evaluate \code{expr}.
#' @param quoted Is \code{expr} a quoted expression (with \code{quote()})? This
#'   is useful if you want to save an expression in a variable.
#' @export
#' @return Components for use inside a Shiny app.
#' @examples
#' if (require("shiny") && interactive()) {
#' ui <- fluidPage(
#'   visual_diff_output("diff")
#' )
#'
#' server <- function(input, output, session) {
#'   path1 <- tempfile()
#'   path2 <- tempfile()
#'   writeLines(letters, path1)
#'   writeLines(letters[-13], path2)
#'
#'   output$diff <- visual_diff_render(visual_diff(path1, path2))
#' }
#'
#' shinyApp(ui, server)
#' }
visual_diff_output <- function(outputId, width = "100%", height = "400px") {
  htmlwidgets::shinyWidgetOutput(
    outputId,
    "visual_diff",
    width = width,
    height = height,
    package = "diffviewer"
  )
}

#' @rdname visual_diff_output
#' @export
visual_diff_render <- function(expr, env = parent.frame(), quoted = FALSE) {
  if (!quoted) {
    expr <- substitute(expr)
  }
  htmlwidgets::shinyRenderWidget(expr, visual_diff_output, env, quoted = TRUE)
}