rubocop: Discourage the use of FileUtils.rm_rf

- This cop checks for the use of `FileUtils.rm_rf` and suggests using
  `FileUtils.rm_r` because we should know if we couldn't delete a
  thing for some reason, not just force it.

Library/Homebrew/rubocops/all.rb

@@ -8,6 +8,7 @@ require_relative "compact_blank"
 require_relative "io_read"
 require_relative "move_to_extend_os"
 require_relative "negate_include"
+require_relative "no_fileutils_rmrf"
 require_relative "presence"
 require_relative "present"
 require_relative "safe_navigation_with_blank"

Library/Homebrew/rubocops/no_fileutils_rmrf.rb

@@ -0,0 +1,27 @@
+# typed: true
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Homebrew
+      # This cop checks for the use of `FileUtils.rm_rf` and recommends `FileUtils.rm_r`.
+      class NoFileutilsRmrf < Base
+        extend AutoCorrector
+
+        MSG = "Use `FileUtils.rm_r` instead of `FileUtils.rm_rf`."
+
+        def_node_matcher :fileutils_rm_rf?, <<~PATTERN
+          (send (const {nil? cbase} :FileUtils) :rm_rf ...)
+        PATTERN
+
+        def on_send(node)
+          return unless fileutils_rm_rf?(node)
+
+          add_offense(node) do |corrector|
+            corrector.replace(node.loc.expression, "FileUtils.rm_r(#{node.arguments.first.source})")
+          end
+        end
+      end
+    end
+  end
+end

Library/Homebrew/test/rubocops/no_fileutils_rmrf_spec.rb

@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+require "rubocops/no_fileutils_rmrf"
+
+RSpec.describe RuboCop::Cop::Homebrew::NoFileutilsRmrf do
+  subject(:cop) { described_class.new }
+
+  it "registers an offense when using FileUtils.rm_rf" do
+    expect_offense(<<~RUBY)
+      FileUtils.rm_rf("path/to/directory")
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Homebrew/NoFileutilsRmrf: Use `FileUtils.rm_r` instead of `FileUtils.rm_rf`.
+    RUBY
+  end
+
+  it "autocorrects" do
+    corrected = autocorrect_source(<<~RUBY)
+      FileUtils.rm_rf("path/to/directory")
+    RUBY
+
+    expect(corrected).to eq(<<~RUBY)
+      FileUtils.rm_r("path/to/directory")
+    RUBY
+  end
+
+  it "does not register an offense when using FileUtils.rm_r" do
+    expect_no_offenses(<<~RUBY)
+      FileUtils.rm_r("path/to/directory")
+    RUBY
+  end
+end