class RuboCop::Cop::Gemspec::RequiredRubyVersion

Checks that ‘required_ruby_version` in a gemspec file is set to a valid value (non-blank) and matches `TargetRubyVersion` as set in RuboCop’s configuration for the gem.

This ensures that RuboCop is using the same Ruby version as the gem.

@example

# When `TargetRubyVersion` of .rubocop.yml is `2.5`.

# bad
Gem::Specification.new do |spec|
  # no `required_ruby_version` specified
end

# bad
Gem::Specification.new do |spec|
  spec.required_ruby_version = '>= 2.4.0'
end

# bad
Gem::Specification.new do |spec|
  spec.required_ruby_version = '>= 2.6.0'
end

# bad
Gem::Specification.new do |spec|
  spec.required_ruby_version = ''
end

# good
Gem::Specification.new do |spec|
  spec.required_ruby_version = '>= 2.5.0'
end

# good
Gem::Specification.new do |spec|
  spec.required_ruby_version = '>= 2.5'
end

# accepted but not recommended
Gem::Specification.new do |spec|
  spec.required_ruby_version = ['>= 2.5.0', '< 2.7.0']
end

# accepted but not recommended, since
# Ruby does not really follow semantic versioning
Gem::Specification.new do |spec|
  spec.required_ruby_version = '~> 2.5'
end