Regex Recompiled In Loop (ARCH6073)

Key ruby.performance.regex-recompiled-in-loop · Severity warning · Category performance

Building a pattern with Regexp.new inside a loop body recompiles the regex on every iteration. Compile the constant pattern once outside the loop.

Incorrect

def matches(lines, word)
  lines.select do |line|
    line =~ Regexp.new("\\b#{word}\\b")
  end
end

Correct

def matches(lines, word)
  pattern = Regexp.new("\\b#{word}\\b")
  lines.select { |line| line =~ pattern }
end

Fix

Compile the regular expression once outside the loop or hot path and reuse it.