fixed-regex

Flag a base-R regex call (grepl, grep, sub, gsub, regexpr, gregexpr, regexec) whose pattern is a plain string literal with no regex metacharacter, and add fixed = TRUE—it skips regex compilation and states that the pattern is a literal.

The rule fires only when the callee resolves to base R and no fixed/ignore.case/perl argument is already present. Because a metacharacter-free pattern matches identically either way, the fix (inserting , fixed = TRUE) is safe.

A literal pattern matched as a regex:

grepl("abc", x)

warning: fixed-regex
 --> example.R:1:7
  |
1 | grepl("abc", x)
  |       ^^^^^ `grepl()` with a literal pattern should use `fixed = TRUE`
  = help: Add `fixed = TRUE`.

After applying the fix:

grepl("abc", x, fixed = TRUE)