Should long vectors be formatted with one element per line?

[etiennebacher]

For long vectors of "simple values", expanding one value per line really is a bit too much. For instance, for this vector:

c(
  "a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"
)

air formats it like:

c(
	"a",
	"b",
	"c",
	[...]
	"x",
	"y",
	"z"
)

while it would probably be better (in this particular case) to have:

c(
  "a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", 
  "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"
)

I'm sure there are a ton of counter examples where having one element per line is actually better, but I just wanted to mention this case.

Note that this is particularly visible when formatting the output of dput(). This is what dput(mtcars) gives:

structure(list(mpg = c(21, 21, 22.8, 21.4, 18.7, 18.1, 14.3, 
24.4, 22.8, 19.2, 17.8, 16.4, 17.3, 15.2, 10.4, 10.4, 14.7, 32.4, 
30.4, 33.9, 21.5, 15.5, 15.2, 13.3, 19.2, 27.3, 26, 30.4, 15.8, 
    [...]
    2, 2, 4, 4, 3, 3, 3, 4, 4, 4, 1, 2, 1, 1, 2, 2, 4, 2, 1, 
    2, 2, 4, 6, 8, 2)), row.names = c("Mazda RX4", "Mazda RX4 Wag", 
"Datsun 710", "Hornet 4 Drive", "Hornet Sportabout", "Valiant", 
"Duster 360", "Merc 240D", "Merc 230", "Merc 280", "Merc 280C", 
"Merc 450SE", "Merc 450SL", "Merc 450SLC", "Cadillac Fleetwood", 
"Lincoln Continental", "Chrysler Imperial", "Fiat 128", "Honda Civic", 
"Toyota Corolla", "Toyota Corona", "Dodge Challenger", "AMC Javelin", 
"Camaro Z28", "Pontiac Firebird", "Fiat X1-9", "Porsche 914-2", 
"Lotus Europa", "Ford Pantera L", "Ferrari Dino", "Maserati Bora", 
"Volvo 142E"), class = "data.frame")

This is how styler formats it (61 lines):

structure(list(
  mpg = c(
    21, 21, 22.8, 21.4, 18.7, 18.1, 14.3,
    24.4, 22.8, 19.2, 17.8, 16.4, 17.3, 15.2, 10.4, 10.4, 14.7, 32.4,
    30.4, 33.9, 21.5, 15.5, 15.2, 13.3, 19.2, 27.3, 26, 30.4, 15.8,
    19.7, 15, 21.4
  ), cyl = c(
    6, 6, 4, 6, 8, 6, 8, 4, 4, 6, 6, 8,
    8, 8, 8, 8, 8, 4, 4, 4, 4, 8, 8, 8, 8, 4, 4, 4, 8, 6, 8, 4
  ),
  [...]
), row.names = c(
  "Mazda RX4", "Mazda RX4 Wag",
  "Datsun 710", "Hornet 4 Drive", "Hornet Sportabout", "Valiant",
  "Duster 360", "Merc 240D", "Merc 230", "Merc 280", "Merc 280C",
  "Merc 450SE", "Merc 450SL", "Merc 450SLC", "Cadillac Fleetwood",
  "Lincoln Continental", "Chrysler Imperial", "Fiat 128", "Honda Civic",
  "Toyota Corolla", "Toyota Corona", "Dodge Challenger", "AMC Javelin",
  "Camaro Z28", "Pontiac Firebird", "Fiat X1-9", "Porsche 914-2",
  "Lotus Europa", "Ford Pantera L", "Ferrari Dino", "Maserati Bora",
  "Volvo 142E"
), class = "data.frame")

And this is how air formats it (413 lines):

structure(
	list(
		mpg = c(
			21,
			21,
			22.8,
			21.4,
			18.7,
			[...]
		"Maserati Bora",
		"Volvo 142E"
	),
	class = "data.frame"
)

[lionel-]

We're considering special comments that would let you request specific layouts for a function call.

[maikol-solis]

This is how styler formats it (61 lines):

Just to consider into the discussion that styler does not break lines. Actually, there is a long discussion about this in their repo about how should be the best approach: r-lib/styler#247 (comment)

[lionel-]

I wonder if it's worth making the rules a bit more complicated and use a wrap fill if:

• All arguments are unnamed
• All arguments are shorter than a configurable threshold, e.g. 5