Freeze mutable objects assigned to constants. Open
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Checks whether some constant value isn't a mutable literal (e.g. array or hash).
Strict mode can be used to freeze all constants, rather than just literals. Strict mode is considered an experimental feature. It has not been updated with an exhaustive list of all methods that will produce frozen objects so there is a decent chance of getting some false positives. Luckily, there is no harm in freezing an already frozen object.
From Ruby 3.0, this cop honours the magic comment 'shareableconstantvalue'. When this magic comment is set to any acceptable value other than none, it will suppress the offenses raised by this cop. It enforces frozen state.
NOTE: Regexp and Range literals are frozen objects since Ruby 3.0.
NOTE: From Ruby 3.0, interpolated strings are not frozen when
# frozen-string-literal: true
is used, so this cop enforces explicit
freezing for such strings.
NOTE: From Ruby 3.0, this cop allows explicit freezing of constants when
the shareable_constant_value
directive is used.
Safety:
This cop's autocorrection is unsafe since any mutations on objects that
are made frozen will change from being accepted to raising FrozenError
,
and will need to be manually refactored.
Example: EnforcedStyle: literals (default)
# bad
CONST = [1, 2, 3]
# good
CONST = [1, 2, 3].freeze
# good
CONST = <<~TESTING.freeze
This is a heredoc
TESTING
# good
CONST = Something.new
Example: EnforcedStyle: strict
# bad
CONST = Something.new
# bad
CONST = Struct.new do
def foo
puts 1
end
end
# good
CONST = Something.new.freeze
# good
CONST = Struct.new do
def foo
puts 1
end
end.freeze
Example:
# Magic comment - shareable_constant_value: literal
# bad
CONST = [1, 2, 3]
# good
# shareable_constant_value: literal
CONST = [1, 2, 3]