Assignment linter

Check that the specified operator is used for assignment.

Usage

assignment_linter(operator = "<-", allow_trailing = TRUE)

Arguments

operator

Character vector of valid assignment operators. Defaults to allowing only <-; other valid options are =, <<-, ->, ->>, %<>%; use "any" to denote "allow all operators", in which case

allow_trailing

Logical, default TRUE. If FALSE then assignments aren't allowed at end of lines.

See also

• linters for a complete list of linters available in lintr.

• https://style.tidyverse.org/syntax.html#assignment-1

• https://style.tidyverse.org/pipes.html#assignment-2

Tags

configurable, consistency, default, style

Examples

# will produce lints
lint(
  text = "x = mean(x)",
  linters = assignment_linter()
)
#> <text>:1:3: style: [assignment_linter] Use <- for assignment, not =.
#> x = mean(x)
#>   ^

code_lines <- "1 -> x\n2 ->> y\nz <<- 3"
writeLines(code_lines)
#> 1 -> x
#> 2 ->> y
#> z <<- 3
lint(
  text = code_lines,
  linters = assignment_linter()
)
#> <text>:1:3: style: [assignment_linter] Use <- for assignment, not ->.
#> 1 -> x
#>   ^~
#> <text>:2:3: style: [assignment_linter] Replace ->> by assigning to a specific environment (with assign() or <-) to avoid hard-to-predict behavior.
#> 2 ->> y
#>   ^~~
#> <text>:3:3: style: [assignment_linter] Replace <<- by assigning to a specific environment (with assign() or <-) to avoid hard-to-predict behavior.
#> z <<- 3
#>   ^~~

lint(
  text = "x %<>% as.character()",
  linters = assignment_linter()
)
#> <text>:1:3: style: [assignment_linter] Avoid the assignment pipe %<>%; prefer pipes and assignment in separate steps.
#> x %<>% as.character()
#>   ^~~~

lint(
  text = "x <- 1",
  linters = assignment_linter(operator = "=")
)
#> <text>:1:3: style: [assignment_linter] Use = for assignment, not <-.
#> x <- 1
#>   ^~

# okay
lint(
  text = "x <- mean(x)",
  linters = assignment_linter()
)
#> ℹ No lints found.

code_lines <- "x <- 1\ny <- 2\nz <- 3"
writeLines(code_lines)
#> x <- 1
#> y <- 2
#> z <- 3
lint(
  text = code_lines,
  linters = assignment_linter()
)
#> ℹ No lints found.

# customizing using arguments
code_lines <- "1 -> x\n2 ->> y"
writeLines(code_lines)
#> 1 -> x
#> 2 ->> y
lint(
  text = code_lines,
  linters = assignment_linter(operator = "->")
)
#> <text>:2:3: style: [assignment_linter] Replace ->> by assigning to a specific environment (with assign() or <-) to avoid hard-to-predict behavior.
#> 2 ->> y
#>   ^~~

lint(
  text = "x <<- 1",
  linters = assignment_linter(operator = "<-")
)
#> <text>:1:3: style: [assignment_linter] Replace <<- by assigning to a specific environment (with assign() or <-) to avoid hard-to-predict behavior.
#> x <<- 1
#>   ^~~

writeLines("foo(bar = \n 1)")
#> foo(bar = 
#>  1)
lint(
  text = "foo(bar = \n 1)",
  linters = assignment_linter(allow_trailing = FALSE)
)
#> <text>:1:9: style: [assignment_linter] Assignment = should not be trailing at the end of a line.
#> foo(bar = 
#>         ^

lint(
  text = "x %<>% as.character()",
  linters = assignment_linter(operator = "%<>%")
)
#> ℹ No lints found.

lint(
  text = "x = 1",
  linters = assignment_linter(operator = "=")
)
#> ℹ No lints found.