A lot of the automations I rig up in my code editor depend on decting where the cursor is in a document and using that context to perform helpful operations.

The simplest class of these are functions that are executed using the symbol the cursor is “on” as input. Typically this symbol represents an object name and typical usage would be:

  • calling str() on the object to inspect it
  • calling targets::tar_load() on the object to read it from cache into the global environment
  • Search and open the definition or help of that object.

Simple things that help keep my hands on the keyboard and my head in the flow.

Rigging in RStudio

RStudio poses two challenges in setting these types of things up as keyboard shortcuts:

  1. The user is not permitted to create shortcuts to run arbitrary R code.
  2. The RStudio API does not provide a facility for getting the symbol at the cursor.

To solve 1. we can use Garrick Aden-Buie’s {shrtcts} package. To solve 2. there’s a tiny package I wrote called {atcursor}.

Suppose we desire a shortcut to call head() on the object cursor is on. This is how we could rig that up in ~/.shrtcts.R:

#' head() on cursor object
#'
#' head(symbol or selection)
#'
#' @interactive
function()  {
  target_object <- atcursor::get_word_or_selection()
  eval(parse(text = paste0("head(",target_object,")")))
}

After that we’d:

  1. shrtcts::add_rstudio_shortcuts()
  2. Bind the shortcut to a key. Using Tools -> Modify Keyboard Shortcuts.
  3. Experience the rush of using the shortcut!

Advanced Notes

  • {shrtcts} can also manage the keyboard bindings with an @shortcut tag but add_rstudio_shortcuts() won’t refer to it by default. See the doco if you want to do that.
  • atcursor::get_word_or_selection() will return a symbol the cursor is “insisde” - e.g. on a column inside the span of the string. If the symbol is namespaced the namespace is also returned, e.g: “namespace::symbol”. If the user has made a selection, that is returned, regardless of cursor position.

  • Rather than building text to parse and then eval, sometimes I find it easier to work with expressions. So you coud do like: target_object <- as.symbol(atcursor::get_word_or_selection()) and then build an expression with bquote:

    eval(bquote(
some(complicated(thing(.(target_object))
))

In conclusion

Without getting overly metaphysical: I think these kind of shortcuts make a lot of sense to me because I view the cursor as my avatar in this world of code before me. I navigate that world almost exclusively with keys, so coding is like piloting that little avatar around. To learn about objects or manipulate them, it makes complete sense to cruise up to them and start engaging them in a dialogue of commands, the scope of which is completely unambigous, because my avatar is in the same space as those objects. In this way, my sense of ‘where I am’ in the code is not broken.

Ofcourse it does happen, I have to jump to the console world when I don’t have a binding for what I need to do, but it feels great when I don’t!