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Class: RuboCop::Cop::Style::IdenticalConditionalBranches

Relationships & Source Files
Super Chains via Extension / Inclusion / Inheritance
Class Chain:
self, ::RuboCop::Cop::AutoCorrector, ::RuboCop::Cop::Base, ::RuboCop::ExcludeLimit, NodePattern::Macros, RuboCop::AST::Sexp
Instance Chain:
Inherits: RuboCop::Cop::Base
Defined in: lib/rubocop/cop/style/identical_conditional_branches.rb

Overview

Checks for identical expressions at the beginning or end of each branch of a conditional expression. Such expressions should normally be placed outside the conditional expression - before or after it.

Note
The cop is poorly named and some people might think that it actually checks for duplicated conditional branches. The name will probably be changed in a future major RuboCop release.

Examples:

# bad
if condition
  do_x
  do_z
else
  do_y
  do_z
end

# good
if condition
  do_x
else
  do_y
end
do_z

# bad
if condition
  do_z
  do_x
else
  do_z
  do_y
end

# good
do_z
if condition
  do_x
else
  do_y
end

# bad
case foo
when 1
  do_x
when 2
  do_x
else
  do_x
end

# good
case foo
when 1
  do_x
  do_y
when 2
  # nothing
else
  do_x
  do_z
end

# bad
case foo
in 1
  do_x
in 2
  do_x
else
  do_x
end

# good
case foo
in 1
  do_x
  do_y
in 2
  # nothing
else
  do_x
  do_z
end

Cop Safety Information:

  • Autocorrection is unsafe because changing the order of method invocations may change the behavior of the code. For example:

    if method_that_modifies_global_state # 1
      method_that_relies_on_global_state # 2
      foo                                # 3
    else
      method_that_relies_on_global_state # 2
      bar                                # 3
    end

    In this example, method_that_relies_on_global_state will be moved before method_that_modifies_global_state, which changes the behavior of the program.

Constant Summary

::RuboCop::Cop::Base - Inherited

EMPTY_OFFENSES, RESTRICT_ON_SEND

::RuboCop::Cop::RangeHelp - Included

BYTE_ORDER_MARK, NOT_GIVEN

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::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::RangeHelp - Included

#add_range, #column_offset_between,
#contents_range

A range containing only the contents of a literal with delimiters (e.g.

#directions,
#effective_column

Returns the column attribute of the range, except if the range is on the first line and there’s a byte order mark at the beginning of that line, in which case 1 is subtracted from the column value.

#final_pos, #move_pos, #move_pos_str, #range_between, #range_by_whole_lines, #range_with_comments, #range_with_comments_and_lines, #range_with_surrounding_comma, #range_with_surrounding_space, #source_range

::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

#assignable_condition_value(node) (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/identical_conditional_branches.rb', line 184

def assignable_condition_value(node)
  if node.condition.call_type?
    (receiver = node.condition.receiver) ? receiver.source : node.condition.source
  elsif node.condition.variable?
    node.condition.source
  end
end

#check_branches(node, branches) (private)

Metrics/CyclomaticComplexity, Metrics/PerceivedComplexity

[ GitHub ]

  
# File 'lib/rubocop/cop/style/identical_conditional_branches.rb', line 140

def check_branches(node, branches)
  # return if any branch is empty. An empty branch can be an `if`
  # without an `else` or a branch that contains only comments.
  return if branches.any?(&:nil?)

  tails = branches.map { |branch| tail(branch) }
  check_expressions(node, tails, :after_condition) if duplicated_expressions?(node, tails)

  return if last_child_of_parent?(node) &&
            branches.any? { |branch| single_child_branch?(branch) }

  heads = branches.map { |branch| head(branch) }

  return unless duplicated_expressions?(node, heads)

  condition_variable = assignable_condition_value(node)

  head = heads.first
  if head.assignment?
    # The `send` node is used instead of the `indexasgn` node, so `name` cannot be used.
    # https://github.com/rubocop/rubocop-ast/blob/v1.29.0/lib/rubocop/ast/node/indexasgn_node.rb
    #
    # FIXME: It would be better to update `RuboCop::AST::OpAsgnNode` or its subclasses to
    # handle `self.foo ||= value` as a solution, instead of using `head.node_parts[0].to_s`.
    assigned_value = head.send_type? ? head.receiver.source : head.node_parts[0].to_s

    return if condition_variable == assigned_value
  end

  check_expressions(node, heads, :before_condition)
end

#check_expressions(node, expressions, insert_position) (private)

Metrics/MethodLength, Metrics/PerceivedComplexity

[ GitHub ]

  
# File 'lib/rubocop/cop/style/identical_conditional_branches.rb', line 193

def check_expressions(node, expressions, insert_position)
  return if expressions.any?(&:nil?)

  inserted_expression = false

  expressions.each do |expression|
    add_offense(expression) do |corrector|
      next if node.if_type? && node.ternary?

      range = range_by_whole_lines(expression.source_range, include_final_newline: true)
      corrector.remove(range)
      next if inserted_expression

      if insert_position == :after_condition
        corrector.insert_after(node, "\n#{expression.source}")
      else
        corrector.insert_before(node, "#{expression.source}\n")
      end
      inserted_expression = true
    end
  end
end

#duplicated_expressions?(node, expressions) ⇒ Boolean (private)

Metrics/CyclomaticComplexity, Metrics/PerceivedComplexity

[ GitHub ]

  
# File 'lib/rubocop/cop/style/identical_conditional_branches.rb', line 173

def duplicated_expressions?(node, expressions)
  unique_expressions = expressions.uniq
  return false unless expressions.size >= 1 && unique_expressions.one?

  unique_expression = unique_expressions.first
  return true unless unique_expression&.assignment?

  lhs = unique_expression.child_nodes.first
  node.condition.child_nodes.none? { |n| n.source == lhs.source if n.variable? }
end

#expand_elses(branch) (private)

elsif branches show up in the if node as nested else branches. We need to recursively iterate over all else branches.

[ GitHub ]

  
# File 'lib/rubocop/cop/style/identical_conditional_branches.rb', line 233

def expand_elses(branch)
  if branch.nil?
    [nil]
  elsif branch.if_type?
    _condition, elsif_branch, else_branch = *branch
    expand_elses(else_branch).unshift(elsif_branch)
  else
    [branch]
  end
end

#head(node) (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/identical_conditional_branches.rb', line 248

def head(node)
  node.begin_type? ? node.children.first : node
end

#last_child_of_parent?(node) ⇒ Boolean (private)

Metrics/MethodLength, Metrics/PerceivedComplexity

[ GitHub ]

  
# File 'lib/rubocop/cop/style/identical_conditional_branches.rb', line 217

def last_child_of_parent?(node)
  return true unless (parent = node.parent)

  parent.child_nodes.last == node
end

#message(node) (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/identical_conditional_branches.rb', line 227

def message(node)
  format(MSG, source: node.source)
end

#on_case(node)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/identical_conditional_branches.rb', line 123

def on_case(node)
  return unless node.else? && node.else_branch

  branches = node.when_branches.map(&:body).push(node.else_branch)
  check_branches(node, branches)
end

#on_case_match(node)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/identical_conditional_branches.rb', line 130

def on_case_match(node)
  return unless node.else? && node.else_branch

  branches = node.in_pattern_branches.map(&:body).push(node.else_branch)
  check_branches(node, branches)
end

#on_if(node)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/identical_conditional_branches.rb', line 116

def on_if(node)
  return if node.elsif?

  branches = expand_elses(node.else_branch).unshift(node.if_branch)
  check_branches(node, branches)
end

#single_child_branch?(branch_node) ⇒ Boolean (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/identical_conditional_branches.rb', line 223

def single_child_branch?(branch_node)
  !branch_node.begin_type? || branch_node.children.size == 1
end

#tail(node) (private)

[ GitHub ]

  
# File 'lib/rubocop/cop/style/identical_conditional_branches.rb', line 244

def tail(node)
  node.begin_type? ? node.children.last : node
end