Class: RuboCop::Cop::Lint::NumericOperationWithConstantResult

Inherits:
Base
  • Object
show all
Extended by:
AutoCorrector
Defined in:
lib/rubocop/cop/lint/numeric_operation_with_constant_result.rb

Overview

Certain numeric operations have a constant result, usually 0 or 1. Multiplying a number by 0 will always return 0. Dividing a number by itself or raising it to the power of 0 will always return 1. As such, they can be replaced with that result. These are probably leftover from debugging, or are mistakes. Other numeric operations that are similarly leftover from debugging or mistakes are handled by Lint/UselessNumericOperation.

NOTE: This cop doesn't detect offenses for the - and % operator because it can't determine the type of x. If x is an Array or String, it doesn't perform a numeric operation.

Examples:


# bad
x * 0

# good
0

# bad
x *= 0

# good
x = 0

# bad
x / x
x ** 0

# good
1

# bad
x /= x
x **= 0

# good
x = 1

Constant Summary collapse

MSG = 
'Numeric operation with a constant result detected.'
RESTRICT_ON_SEND = 
%i[* / **].freeze

Instance Attribute Summary

Attributes inherited from Base

#config, #processed_source, #project_index

Instance Method Summary collapse

Methods included from AutoCorrector

support_autocorrect?

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

#abbreviated_assignment_with_constant_result?(node) ⇒ Object 



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# File 'lib/rubocop/cop/lint/numeric_operation_with_constant_result.rb', line 64

def_node_matcher :abbreviated_assignment_with_constant_result?,
'(op-asgn (lvasgn $_lhs) $_operation ({int lvar} $_rhs))'

#on_op_asgn(node) ⇒ Object 



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# File 'lib/rubocop/cop/lint/numeric_operation_with_constant_result.rb', line 80

def on_op_asgn(node)
  return unless (lhs, operation, rhs = abbreviated_assignment_with_constant_result?(node))
  return unless (result = constant_result?(lhs, operation, rhs))

  add_offense(node) do |corrector|
    corrector.replace(node, "#{lhs} = #{result}")
  end
end

#on_send(node) ⇒ Object Also known as: on_csend 



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# File 'lib/rubocop/cop/lint/numeric_operation_with_constant_result.rb', line 67

def on_send(node)
  # Safe navigation short-circuits to `nil` when the receiver is `nil`, so the
  # result is not constant and replacing it with `0`/`1` would change behavior.
  return if node.csend_type?
  return unless (lhs, operation, rhs = operation_with_constant_result?(node))
  return unless (result = constant_result?(lhs, operation, rhs))

  add_offense(node) do |corrector|
    corrector.replace(node, result.to_s)
  end
end

#operation_with_constant_result?(node) ⇒ Object 



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# File 'lib/rubocop/cop/lint/numeric_operation_with_constant_result.rb', line 60

def_node_matcher :operation_with_constant_result?,
'(call (call nil? $_lhs) $_operation ({int | call nil?} $_rhs))'