Class: RuboCop::Cop::Style::MutableConstant

Inherits:

Base

• Object
• Base
• RuboCop::Cop::Style::MutableConstant

Extended by:

AutoCorrector

Includes:

ConfigurableEnforcedStyle, FrozenStringLiteral

Defined in:

lib/rubocop/cop/style/mutable_constant.rb

Overview

Checks whether some constant value isn’t a mutable literal (e.g. array or hash).

When the ‘Recursive` option is enabled, mutable literals nested inside arrays and hashes are also frozen, so an offense on the outermost unfrozen literal will autocorrect every nested mutable literal as well. When the outer literal already has `.freeze` appended, the cop descends into it and reports each outermost unfrozen literal underneath. The option is disabled by default to preserve existing behavior; opt in to get strict nested freezing.

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 ‘shareable_constant_value’. 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.

Examples:

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

Recursive: false (default)

# good - only the outer container needs to be frozen
CONST = [{ a: [], b: 'foo' }].freeze

Recursive: true

# bad - nested mutable literals must be frozen too
CONST = [{ a: [], b: 'foo' }].freeze

# good
CONST = [{ a: [].freeze, b: 'foo'.freeze }.freeze].freeze

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

# Magic comment - shareable_constant_value: literal

# bad
CONST = [1, 2, 3]

# good
# shareable_constant_value: literal
CONST = [1, 2, 3]

Constant Summary

MSG =

'Freeze mutable objects assigned to constants.'

Constants included from FrozenStringLiteral

FrozenStringLiteral::FROZEN_STRING_LITERAL_ENABLED

Constants inherited from Base

Base::RESTRICT_ON_SEND

Instance Attribute Summary

Attributes inherited from Base

#config, #processed_source, #project_index

Instance Method Summary

• #on_casgn(node) ⇒ Object

Methods included from AutoCorrector

support_autocorrect?

Methods included from ConfigurableEnforcedStyle

#alternative_style, #alternative_styles, #ambiguous_style_detected, #correct_style_detected, #detected_style, #detected_style=, #no_acceptable_style!, #no_acceptable_style?, #opposite_style_detected, #style, #style_configured?, #style_detected, #style_parameter_name, #supported_styles, #unexpected_style_detected

Methods included from FrozenStringLiteral

frozen_string_literal?, frozen_string_literal_comment_exists?, frozen_string_literal_specified?, frozen_string_literals_disabled?, frozen_string_literals_enabled?, leading_comment_lines, leading_magic_comments, uninterpolated_heredoc?, uninterpolated_string?

Methods inherited from Base

#active_support_extensions_enabled?, #add_global_offense, #add_offense, #always_autocorrect?, autocorrect_incompatible_with, badge, #begin_investigation, #callbacks_needed, callbacks_needed, #config_to_allow_offenses, #config_to_allow_offenses=, #contextual_autocorrect?, #cop_config, cop_name, #cop_name, department, documentation_url, exclude_from_registry, #excluded_file?, #external_dependency_checksum, inherited, #initialize, #inspect, joining_forces, lint?, match?, #message, #offenses, #on_investigation_end, #on_new_investigation, #on_other_file, #parse, #parser_engine, #ready, #relevant_file?, requires_gem, #string_literals_frozen_by_default?, support_autocorrect?, support_multiple_source?, #target_gem_version, #target_rails_version, #target_ruby_version

Methods included from ExcludeLimit

cop_dir_for, #exclude_limit, read_limits

Methods included from AutocorrectLogic

#autocorrect?, #autocorrect_enabled?, #autocorrect_requested?, #autocorrect_with_disable_uncorrectable?, #correctable?, #disable_uncorrectable?, #safe_autocorrect?

Methods included from IgnoredNode

#ignore_node, #ignored_node?, #part_of_ignored_node?

Methods included from Util

silence_warnings

Constructor Details

This class inherits a constructor from RuboCop::Cop::Base

Instance Method Details

#on_casgn(node) ⇒ Object

# File 'lib/rubocop/cop/style/mutable_constant.rb', line 146

def on_casgn(node)
  if node.expression.nil? # This is only the case for `CONST += ...` or similar
    parent = node.parent
    return unless parent.or_asgn_type? # We only care about `CONST ||= ...`

    on_assignment(parent.children.last)
  else
    on_assignment(node.expression)
  end
end