metaprogramming - substitute

[Polkas]

I will be glad if you consider to support one of the metaprogramming scenario.
Unfortunately I find out quite dangerous side effect of styler styling.

Example where we will expect the styler to NOT add brackets in %>% pipeline:

styler::style_text('substitute(DATA %>% FUN_EXPR, env = list(FUN_EXPR = call("FUN")))')
# substitute(DATA %>% FUN_EXPR(), env = list(FUN_EXPR = call("FUN")))
# whereas should be neutral
# substitute(DATA %>% FUN_EXPR, env = list(FUN_EXPR = call("FUN")))

The usage of bquote might be a solution here nevertheless substitute is way more efficient:

> microbenchmark::microbenchmark(bquote = {bquote(x <- .(letters))}, substitute = {substitute(x <- ll, list(ll = letters))})
#Unit: nanoseconds
#       expr  min   lq    mean median     uq   max neval cld
#     bquote 4387 4510 4809.71   4592 4674.0 24313   100   b
# substitute  164  246  281.67    246  266.5  2378   100  a 

[lorenzwalthert]

Thanks @Polkas. Are you suggesting that the rule that adds () should not be applied inside substitute()? This might be feasible.

Also, this substitution is using base R. {styler} is a tidyverse focussed formatter and there are other (and probably better) tools to do this, namely tidy evaluation. Not sure the problem would occur there too.

[Polkas]

Thank you very much for a quick response.
Yes, a rule that adds () should not be applied inside substitute(). I will be glad if it could be applied. The code design is not assumed to use tidy rules. Thanks

[lorenzwalthert]

Ok, just for the sake of completeness, can you provide a reprex where the current {styler} behavior fails? I.e. changes the result of running the code?

[Polkas]

Reprex, which is showing that finally we get FUN_head()() (variable styled_expr) instead of FUN_head() (variable expr):

library(magrittr)
FUN_head <- function(x) head(x)
expr <- substitute(airquality %>% FUN_EXPR, env = list(FUN_EXPR = call("FUN_head")))
print(expr)
#> airquality %>% FUN_head()
eval(expr)
#>   Ozone Solar.R Wind Temp Month Day
#> 1    41     190  7.4   67     5   1
#> 2    36     118  8.0   72     5   2
#> 3    12     149 12.6   74     5   3
#> 4    18     313 11.5   62     5   4
#> 5    NA      NA 14.3   56     5   5
#> 6    28      NA 14.9   66     5   6
styled_expr_str <- styler::style_text('substitute(airquality %>% FUN_EXPR, env = list(FUN_EXPR = call("FUN_head")))')
# double eval as frist one return only result of substitute
styled_expr <- eval(str2lang(styled_expr_str))
print(styled_expr)
#> airquality %>% FUN_head()()
eval(styled_expr)
#> Error in head(x): argument "x" is missing, with no default

^{Created on 2021-12-15 by the reprex package (v2.0.1)}

[lorenzwalthert]

So, we can solve this when substitute() is explicitly called, but it it is a placeholder itself, we can't track the reference. I.e. in

placeholder <- substitute
placeholder(x %>% y, env =list(y = call("head")))

y -> y() with applying {styler}. Don't think this can be solved -.- We had to disable the rule completely within function calls.

[Polkas]

I understand this is only a regex rule so my expectancy was not so high. I think an update of the case where the usage of substitute is direct will be more than enough. Thank you once more for the support in this issue.