R6 member name completion after Dollar on "Tab" keystroke

[jmp75]

Context

I am the author of the rClr (R - .NET interop) package and considering R6 as a way to expose .NET objects via reference classes. I started using the R reference classes some months ago but bumped into several issues. R6 may be a better option.

Feature request

One important feature I'd think is a boon to user experience is code completion after the $ separator on object members. I think these are features of the Rcpp, rJava and rJavax packages, using utils::.DollarNames and related facilities. I am not familiar with the details.

I have forked R6, and may consider implementing these features, unless:

• There are design considerations against supporting it
• Someone else is already doing is, or feels more familiar with the mechanics to tackle it.

[gaborcsardi]

:thumbsup:

[wch]

Interesting -- I wasn't aware of utils::.DollarNames. For the record, this is also related to #30.

[wch]

Tab completions appear to just work with R6 in R 3.2.1, so maybe there was a change in R to support this?

I've tested this in RStudio and with R at the terminal, both in Linux.

AC <- R6Class("AC",
  public = list(
    x1 = 1,
    x2 = 2
  )
)
a <- AC$new()

# Press [tab] after this
a$

[peekxc]

Very minor request, but is it possible to extend this in a nested manner?

Consider amended example:

AC <- R6Class("AC",
              public = list(
                  x1 = function(){ invisible(self) },
                  x2 = 2
              )
)
a <- AC$new()

While code completion works for x1, one cannot see x2 or any other members with, e.g.

a$x1()$

Whereas this is possible w/ magrittr pipes, e.g. mtcars %>% select(mpg, cyl) %>% select( ) # [tab] yields remaining columns

I understand this is a bit trickier, and only works if the member function returns self, but nonetheless would be nice for workflows which naturally rely on R6's method chaining.