In auto-correct mode, RuboCop will try to automatically fix offenses:
$ rubocop -a
For some offenses, it is not possible to implement automatic correction.
Some automatic corrections that are possible have not been implemented yet.
$ rubocop --safe-auto-correct
In RuboCop 0.60, we began to annotate cops as
Safe or not safe. Eventually,
the safety of each cop will be determined.
- Safe (true/false) - indicates whether the cop can yield false positives (by design) or not.
- SafeAutoCorrect (true/false) - indicates whether the auto-correct the cop does is safe (equivalent) by design. https://github.com/rubocop-hq/rubocop/issues/5978#issuecomment-395958738
If a cop is annotated as "not safe", it will be omitted.
Example of Unsafe Cop
array =  array << 'Foo' << 'Bar' << 'Baz' puts array.join('-')
Style/LineEndConcatenation will correct the above to:
array =  array << 'Foo' \ 'Bar' \ 'Baz' puts array.join('-')
Therefore, in this (unusual) scenario,
Style/LineEndConcatenation is unsafe.
(This is a contrived example. Real code would use
%w for an array of string