class RuboCop::Cop::Style::IdenticalConditionalBranches

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.

@safety

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

[source,ruby]
----
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.

@example

# 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

Constants

MSG

Public Instance Methods

on_case(node) click to toggle source
# 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) click to toggle source
# 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) click to toggle source
# 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

Private Instance Methods

check_branches(node, branches) click to toggle source
# File lib/rubocop/cop/style/identical_conditional_branches.rb, line 139
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)

  heads = branches.map { |branch| head(branch) }
  check_expressions(node, heads, :before_condition) if duplicated_expressions?(node, heads)
end
check_expressions(node, expressions, insert_position) click to toggle source
# File lib/rubocop/cop/style/identical_conditional_branches.rb, line 162
def check_expressions(node, expressions, insert_position) # rubocop:disable Metrics/MethodLength
  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) click to toggle source
# File lib/rubocop/cop/style/identical_conditional_branches.rb, line 151
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) click to toggle source

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

# File lib/rubocop/cop/style/identical_conditional_branches.rb, line 189
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) click to toggle source
# File lib/rubocop/cop/style/identical_conditional_branches.rb, line 204
def head(node)
  node.begin_type? ? node.children.first : node
end
message(node) click to toggle source
# File lib/rubocop/cop/style/identical_conditional_branches.rb, line 183
def message(node)
  format(MSG, source: node.source)
end
tail(node) click to toggle source
# File lib/rubocop/cop/style/identical_conditional_branches.rb, line 200
def tail(node)
  node.begin_type? ? node.children.last : node
end