Conflicting lintr rules with alist and explicitly missing arguments

[richfitz]

This is pretty niche but shows up a conflicting pair of rules:

> lintr::lint("alist(a =)\n")
<text>:1:9: style: Put spaces around all infix operators.
alist(a =)
        ^~
> lintr::lint("alist(a = )\n")
<text>:1:10: style: Do not place spaces around code in parentheses or square brackets.
alist(a = )
         ^
> lintr::lint("alist(a =, b = NULL)\n")
<text>:1:9: style: Put spaces around all infix operators.
alist(a =, b = NULL)
        ^~
> lintr::lint("alist(a = , b = NULL)\n")
<text>:1:11: style: Commas should never have a space before.
alist(a = , b = NULL)

So for arguments that are "explicitly missing" there is no way of satisfying the default set of linter rules - we must and cannot have a space following the =, for cases that are within or at the end of an argument list.

The above behaviour is triggered in both the cran version (2.0.1) and current github (2.0.1.9000, eece3c1)

[AshesITR]

This is related to #532

[richfitz]

Ah, I'd looked though for issues about commas but managed to miss that!

[AshesITR]

Your examples show that the commas_linter must also be fixed, not only the spaces_inside_linter so thanks 👍

[MichaelChirico]

Is this in fact the same as #532?

[AshesITR]

#532 is a special case of this. Closing #532

[MichaelChirico]

This is basically the same as #708 -- there, we now allow your second usage, but not your first:

lintr::lint("switch(a = , b = 2)\n") # doesn't lint
lintr::lint("switch(a =, b = 2)\n")
# <text>:1:10: style: [infix_spaces_linter] Put spaces around all infix operators.
# switch(a =, b = 2)
#          ^

This aligns with {styler}:

styler::style_text("switch(a = , b = 2)\nswitch(a =, b = 2)\nalist(a = )\nalist(a =)")
# switch(a = ,
#   b = 2
# )
# switch(a = ,
#   b = 2
# )
# alist(a = )
# alist(a = )