fixed_regex_linter {lintr}

Require usage of fixed=TRUE in regular expressions where appropriate

Description

Invoking a regular expression engine is overkill for cases when the search pattern only involves static patterns.

Usage

fixed_regex_linter(allow_unescaped = FALSE)

Arguments

allow_unescaped

Logical, default FALSE. If TRUE, only patterns that require regex escapes (e.g. "\\$" or "[$]") will be linted. See examples.

Details

NB: for stringr functions, that means wrapping the pattern in stringr::fixed().

NB: this linter is likely not able to distinguish every possible case when a fixed regular expression is preferable, rather it seeks to identify likely cases. It should never report false positives, however; please report false positives as an error.

Tags

best_practices, configurable, efficiency, readability

See Also

linters for a complete list of linters available in lintr.

Examples

# will produce lints
code_lines <- 'gsub("\\\\.", "", x)'
writeLines(code_lines)
lint(
  text = code_lines,
  linters = fixed_regex_linter()
)

lint(
  text = 'grepl("a[*]b", x)',
  linters = fixed_regex_linter()
)

lint(
  text = 'grepl("a[*]b", x)',
  linters = fixed_regex_linter(allow_unescaped = TRUE)
)

code_lines <- 'stringr::str_subset(x, "\\\\$")'
writeLines(code_lines)
lint(
  text = code_lines,
  linters = fixed_regex_linter()
)

lint(
  text = 'grepl("Munich", address)',
  linters = fixed_regex_linter()
)

# okay
code_lines <- 'gsub("\\\\.", "", x, fixed = TRUE)'
writeLines(code_lines)
lint(
  text = code_lines,
  linters = fixed_regex_linter()
)

lint(
  text = 'grepl("a*b", x, fixed = TRUE)',
  linters = fixed_regex_linter()
)

lint(
  text = 'stringr::str_subset(x, stringr::fixed("$"))',
  linters = fixed_regex_linter()
)

lint(
  text = 'grepl("Munich", address, fixed = TRUE)',
  linters = fixed_regex_linter()
)

lint(
  text = 'grepl("Munich", address)',
  linters = fixed_regex_linter(allow_unescaped = TRUE)
)