Build a RStudio addin to debug pipe chains

I posted this question first on SO but it didn't have much success.

On second thought it may be a better fit here (slightly modified from the SO version).

I wrote a function that helps executing pipe chains step by step.

To use it the users has to copy the instruction to clipboard, then execute the function, and move to the console to proceed.

I would like to build an addin that would allow me to select the instructions and run the function with Ctrl + P without the awkward steps.

Ideally, the addin would :

  1. capture the selection
  2. run the function
  3. move the cursor to the console
  4. be triggered by Ctrl + P

I believe it's extremely similar to what the reprex addin is doing but I don't know where to start as I'm 100% new to addins.

I looked into rstudioapi::getActiveDocumentContext() but there was nothing there of interest to me.

How can I make this work ?

The function

debug_pipe <- function(.expr){
  .pchain <-
    if(missing(.expr)) readClipboard() # windows only , else try clipr::read_clip()
  else deparse(substitute(.expr))
  .lhs    <- if(grepl("^\\s*[[:alnum:]_.]*\\s*<-",.pchain[1])){
  } else NA
  .pchain <- sub("[^%]*<-\\s*","",.pchain)        # remove lhs of assignment if exists
  .pchain <- paste(.pchain,collapse=" ")          # collapse 
  .pchain <- gsub("\\s+"," ",.pchain)             # multiple spaces to single 
  .pchain <- strsplit(.pchain,"\\s*%>%\\s*")[[1]] # split by pipe
  .pchain <- as.list(.pchain)
  for (i in rev(seq_along(.pchain))){
    # function to count matches
    .f <- function(x) sum(gregexpr(x,.pchain[i],fixed=TRUE)[[1]] !=-1)
    # check if unbalanced operators
    .balanced <-
      all(c(.f("{"),.f("("),.f("[")) == c(.f("}"),.f(")"),.f("]"))) &
      ! .f("'") %% 2 &
      ! .f('"') %% 2
    if(!.balanced) {
      # if unbalanced, combine with previous
      .pchain[[i-1]] <- paste(.pchain[[i-1]],"%>%", .pchain[[i]])
      .pchain[[i]] <- NULL
  .calls  <- Reduce(                             # build calls to display
    function(x,y) paste0(x," %>%\n  ",y),       
    .pchain, accumulate=TRUE)     
  .xinit  <- eval(parse(text=.pchain[1]))      
  .values <- Reduce(function(x,y){               # compute all values
    if (inherits(x,"try-error")) NULL
    else try(eval(parse(text= paste("x %>%", y))),silent = TRUE)},
    .pchain[-1], .xinit, accumulate=TRUE)
  message("press enter to show, 's' to skip, 'q' to quit, lhs can be accessed with `.`")
  for (.i in (seq_along(.pchain))){
    .rdl_ <- readline()
    . <- .values[[.i]]
    # while environment is explored
    while(!.rdl_ %in% c("q","s","")){
      # if not an assignment, should be printed
      if(!grepl("^\\s*[[:alnum:]_.]*\\s*<-",.rdl_)) .rdl_ <- paste0("print(",.rdl_,")")
      # wrap into `try` to safely fail
      .rdl_ <- readline()
    if(.rdl_ == "q")  return(invisible(NULL))
    if(.rdl_ != "s") {
      if (inherits(.values[[.i]],"try-error")) {
        # a trick to be able to use stop without showing that
        # debug_pipe failed in the output
        opt <- options(show.error.messages = FALSE)
      } else
  if(! assign(.lhs,tail(.values,1),envir = parent.frame())

Example code:

    # copy following 4 lines to clipboard, no need to execute
    test <- iris %>%
      slice(1:2) %>%
      select(1:3) %>%

    # or wrap expression
    test <- iris %>%
      slice(1:2) %>%
      select(1:3) %>%

I mostly figured it out, see my answer on SO :

1 Like

Here you go!


This is a cool approach as well! thanks!