reprex Error in (function (x) : object 'y' not found

[zkamvar]

I'm trying to create a reprex example for a code review and I'm running into a weird issue where I can't create a reprex that seems like it should run. Am I just being thick?

Here's my reprex'd reprex attempt showing simultaneously that reprex works and doesn't work.

reprex::reprex({
  library(dplyr)
  library(rlang)
  headselect <- function(x, y) {
    head(dplyr::select(x, !!rlang::enquo(y)))
  }
  wrapper <- function(x, y) {
    headselect(x, y)
  }
  wrapper2 <- function(x, y) {
    headselect(x, !!rlang::enquo(y))
  }
  headselect(iris, Petal.Length)
  wrapper2(iris, Petal.Length)
  wrapper(iris, Petal.Length)
})
#> Error in (function (x) : object 'y' not found

^{Created on 2019-02-07 by the reprex package (v0.2.1)}

Session info

devtools::session_info()
#> ─ Session info ──────────────────────────────────────────────────────────
#>  setting  value                       
#>  version  R version 3.5.2 (2018-12-20)
#>  os       macOS Mojave 10.14.2        
#>  system   x86_64, darwin15.6.0        
#>  ui       X11                         
#>  language (EN)                        
#>  collate  en_US.UTF-8                 
#>  ctype    en_US.UTF-8                 
#>  tz       Asia/Seoul                  
#>  date     2019-02-07                  
#> 
#> ─ Packages ──────────────────────────────────────────────────────────────
#>  package     * version    date       lib source                        
#>  assertthat    0.2.0      2017-04-11 [1] CRAN (R 3.5.0)                
#>  backports     1.1.3      2018-12-14 [1] CRAN (R 3.5.0)                
#>  callr         3.1.1      2018-12-21 [1] CRAN (R 3.5.0)                
#>  cli           1.0.1      2018-09-25 [1] CRAN (R 3.5.0)                
#>  crayon        1.3.4      2017-09-16 [1] CRAN (R 3.5.0)                
#>  desc          1.2.0      2018-05-01 [1] CRAN (R 3.5.0)                
#>  devtools      2.0.1      2018-10-26 [1] CRAN (R 3.5.1)                
#>  digest        0.6.18     2018-10-10 [1] CRAN (R 3.5.0)                
#>  evaluate      0.12       2018-10-09 [1] CRAN (R 3.5.0)                
#>  fs            1.2.6      2018-08-23 [1] CRAN (R 3.5.0)                
#>  glue          1.3.0      2018-07-17 [1] CRAN (R 3.5.0)                
#>  highr         0.7        2018-06-09 [1] CRAN (R 3.5.0)                
#>  htmltools     0.3.6      2017-04-28 [1] CRAN (R 3.5.0)                
#>  knitr         1.21       2018-12-10 [1] CRAN (R 3.5.2)                
#>  magrittr      1.5        2014-11-22 [1] CRAN (R 3.5.0)                
#>  memoise       1.1.0      2017-04-21 [1] CRAN (R 3.5.0)                
#>  pkgbuild      1.0.2      2018-10-16 [1] CRAN (R 3.5.0)                
#>  pkgload       1.0.2      2018-10-29 [1] CRAN (R 3.5.0)                
#>  prettyunits   1.0.2      2015-07-13 [1] CRAN (R 3.5.0)                
#>  processx      3.2.1      2018-12-05 [1] CRAN (R 3.5.0)                
#>  ps            1.3.0      2018-12-21 [1] CRAN (R 3.5.0)                
#>  R6            2.3.0      2018-10-04 [1] CRAN (R 3.5.0)                
#>  Rcpp          1.0.0      2018-11-07 [1] CRAN (R 3.5.0)                
#>  remotes       2.0.2      2018-10-30 [1] CRAN (R 3.5.0)                
#>  reprex        0.2.1      2018-09-16 [1] CRAN (R 3.5.0)                
#>  rlang         0.3.1      2019-01-08 [1] CRAN (R 3.5.2)                
#>  rmarkdown     1.11       2018-12-08 [1] CRAN (R 3.5.0)                
#>  rprojroot     1.3-2      2018-01-03 [1] CRAN (R 3.5.0)                
#>  sessioninfo   1.1.1      2018-11-05 [1] CRAN (R 3.5.1)                
#>  stringi       1.2.4      2018-07-20 [1] CRAN (R 3.5.0)                
#>  stringr       1.3.1      2018-05-10 [1] CRAN (R 3.5.0)                
#>  testthat      2.0.1      2018-10-13 [1] CRAN (R 3.5.0)                
#>  usethis       1.4.0.9000 2018-10-06 [1] Github (r-lib/usethis@1e3c6a6)
#>  withr         2.1.2      2018-03-15 [1] CRAN (R 3.5.0)                
#>  xfun          0.4        2018-10-23 [1] CRAN (R 3.5.0)                
#>  yaml          2.2.0      2018-07-25 [1] CRAN (R 3.5.0)                
#> 
#> [1] /Users/zhian/R
#> [2] /Library/Frameworks/R.framework/Versions/3.5/Resources/library

[jennybc]

Since rlang::enexpr() supports quasiquotation, I don't think you can provide code that uses !! to reprex() as an expression, as you do above. Input that comes as an expression is captured via rlang::enexpr().

This same code can be successfully reprex()ed by using the clipboard or a source file.

cc @lionel-

[jennybc]

This makes me wonder if I should be capturing expression input with quote(), as I used to do 🤔

[lionel-]

I think you're right, it makes sense to use substitute() in that case.

[jennybc]

I think you're right, it makes sense to use substitute() in that case.

Yeah, sorry, that's what I meant and what I used to use. I had just been fiddling with top-level code and had quote() on the mind.

So shall I go back to substitute() here then?

reprex/R/reprex.R

Line 278 in d03e0ef

x_expr <- enexpr(x)

[lionel-]

Yes substitute() instead of enexpr() there should work exactly the same way, minus the unquoting. The !! should be properly processed by the relevant quoting functions when you evaluate later on.

This will also make the evaluation timing in reprex examples more accurate. Currently the unquoted stuff could depend on local state and go unnoticed because reprex only sees constants.