EndWith/StartWith autocorrects are not nil-safe

[dduugg]

The EndWith/StartWith autocorrects do not contemplate nil. I propose modifying them to behave like RegexpMatch (which corrects do_something if pattern =~ param into do_something if pattern&.match?(path)

Expected behavior

do_something if var =~ /\A#/ should autocorrect to do_something if var&.start_with?('#')

Since it appears rubocop will soon end support for pre-2.3 ruby, I propose only fixing this for ruby 2.3 and above (where safe navigation is available).

Actual behavior

do_something if var =~ /\A#/ autocorrects to do_something if var.start_with?('#'). The correction will now raise a NoMethodError when var is nil, where previously the condition would simply evaluate to nil.

Steps to reproduce the problem

Invoke rubocop -a --only Performance/StartWith on a file containing do_something if var =~ /\A#/, with a .rubocop.yml file containing:

require:
  - rubocop-performance
Performance/StartWith:
  AutoCorrect: true

RuboCop version

Include the output of rubocop -V or bundle exec rubocop -V if using Bundler. Here's an example:

$ bundle exec rubocop -V
0.68.0 (using Parser 2.6.0.0, running on ruby 2.4.5 x86_64-darwin17)

[koic]

This cop is marked SafeAutoCorrect: false and unmarked AutoCorrect: false. So I will close this issue. Thank you.