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Class: RuboCop::Cop::Style::SlicingWithRange

Relationships & Source Files
Super Chains via Extension / Inclusion / Inheritance
Class Chain:
Instance Chain:
Inherits: RuboCop::Cop::Base
Defined in: lib/rubocop/cop/style/slicing_with_range.rb

Overview

Checks that arrays are not sliced with the redundant ary[0..-1], replacing it with ary, and ensures arrays are sliced with endless ranges instead of ary[start..-1] on Ruby 2.6+, and with beginless ranges instead of ary[nil..end] on Ruby 2.7+.

Examples:

# bad
items[0..-1]
items[0..nil]
items[0...nil]

# good
items

# bad
items[1..-1]   # Ruby 2.6+
items[1..nil]  # Ruby 2.6+

# good
items[1..]     # Ruby 2.6+

# bad
items[nil..42] # Ruby 2.7+

# good
items[..42]    # Ruby 2.7+
items[0..42]   # Ruby 2.7+

Cop Safety Information:

  • This cop is unsafe because x..-1 and x.. are only guaranteed to be equivalent for Array#[], String#[], and the cop cannot determine what class the receiver is.

    For example:

    sum = proc { |ary| ary.sum }
    sum[-3..-1] # => -6
    sum[-3..] # Hangs forever

Constant Summary

::RuboCop::Cop::Base - Inherited

EMPTY_OFFENSES, RESTRICT_ON_SEND

Class Attribute Summary

::RuboCop::Cop::AutoCorrector - Extended

::RuboCop::Cop::Base - Inherited

.gem_requirements, .lint?,
.support_autocorrect?

Returns if class supports autocorrect.

.support_multiple_source?

Override if your cop should be called repeatedly for multiple investigations Between calls to on_new_investigation and on_investigation_end, the result of processed_source will remain constant.

Class Method Summary

::RuboCop::Cop::TargetRubyVersion - Extended

::RuboCop::Cop::Base - Inherited

.autocorrect_incompatible_with

List of cops that should not try to autocorrect at the same time as this cop.

.badge

Naming.

.callbacks_needed, .cop_name, .department,
.documentation_url

Returns an url to view this cops documentation online.

.exclude_from_registry

Call for abstract Cop classes.

.inherited,
.joining_forces

Override and return the Force class(es) you need to join.

.match?

Returns true if the cop name or the cop namespace matches any of the given names.

.new,
.requires_gem

Register a version requirement for the given gem name.

.restrict_on_send

::RuboCop::ExcludeLimit - Extended

exclude_limit

Sets up a configuration option to have an exclude limit tracked.

transform

Instance Attribute Summary

Instance Method Summary

::RuboCop::Cop::Base - Inherited

#add_global_offense

Adds an offense that has no particular location.

#add_offense

Adds an offense on the specified range (or node with an expression) Unless that offense is disabled for this range, a corrector will be yielded to provide the cop the opportunity to autocorrect the offense.

#begin_investigation

Called before any investigation.

#callbacks_needed,
#cop_config

Configuration Helpers.

#cop_name, #excluded_file?,
#external_dependency_checksum

This method should be overridden when a cop’s behavior depends on state that lives outside of these locations:

#inspect
#message

Gets called if no message is specified when calling add_offense or add_global_offense Cops are discouraged to override this; instead pass your message directly.

#name

Alias for Base#cop_name.

#offenses,
#on_investigation_end

Called after all on_…​

#on_new_investigation

Called before all on_…​

#on_other_file

Called instead of all on_…​

#parse

There should be very limited reasons for a Cop to do it’s own parsing.

#parser_engine,
#ready

Called between investigations.

#relevant_file?, #target_rails_version, #target_ruby_version, #annotate, #apply_correction, #attempt_correction,
#callback_argument

Reserved for Cop::Cop.

#complete_investigation

Called to complete an investigation.

#correct, #current_corrector,
#current_offense_locations

Reserved for Commissioner:

#current_offenses, #currently_disabled_lines, #custom_severity, #default_severity, #disable_uncorrectable, #enabled_line?, #file_name_matches_any?, #find_message, #find_severity, #range_for_original, #range_from_node_or_range,
#reset_investigation

Actually private methods.

#use_corrector

::RuboCop::Cop::AutocorrectLogic - Included

::RuboCop::Cop::IgnoredNode - Included

Constructor Details

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

Instance Method Details

#beginless(range_node) (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/slicing_with_range.rb', line 111

def beginless(range_node)
  "[#{range_node.loc.operator.source}#{range_node.end.source}]"
end

#endless(range_node) (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/slicing_with_range.rb', line 107

def endless(range_node)
  "[#{range_node.begin.source}#{range_node.loc.operator.source}]"
end

#offense_message_with_removal_range(range_node, selector) (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/slicing_with_range.rb', line 93

def offense_message_with_removal_range(range_node, selector)
  if range_from_zero_till_minus_one?(range_node)
    [format(MSG_USELESS_RANGE, prefer: selector.source), selector]
  elsif range_till_minus_one?(range_node)
    [
      format(MSG, prefer: endless(range_node), current: selector.source), range_node.end
    ]
  elsif range_from_zero?(range_node) && target_ruby_version >= 2.7
    [
      format(MSG, prefer: beginless(range_node), current: selector.source), range_node.begin
    ]
  end
end

#on_send(node)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/slicing_with_range.rb', line 77

def on_send(node)
  return unless node.arguments.one?

  range_node = node.first_argument
  selector = node.loc.selector
  unless (message, removal_range = offense_message_with_removal_range(range_node, selector))
    return
  end

  add_offense(selector, message: message) do |corrector|
    corrector.remove(removal_range)
  end
end

#range_from_zero?(node)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/slicing_with_range.rb', line 73

def_node_matcher :range_from_zero?, <<~PATTERN
  (irange nil !nil?)
PATTERN

#range_from_zero_till_minus_one?(node)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/slicing_with_range.rb', line 57

def_node_matcher :range_from_zero_till_minus_one?, <<~PATTERN
  {
    (irange (int 0) {(int -1) nil})
    (erange (int 0) nil)
  }
PATTERN

#range_till_minus_one?(node)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/slicing_with_range.rb', line 65

def_node_matcher :range_till_minus_one?, <<~PATTERN
  {
    (irange !nil? {(int -1) nil})
    (erange !nil? nil)
  }
PATTERN