This cop checks if the length of a method exceeds some maximum value. Comment lines can optionally be ignored. The maximum allowed length is configurable.

A method with Too Many Statements is any method that has a large number of lines.

Too Many Statements warns about any method that has more than 5 statements. Reek's smell detector for Too Many Statements counts +1 for every simple statement in a method and +1 for every statement within a control structure (if, else, case, when, for, while, until, begin, rescue) but it doesn't count the control structure itself.

So the following method would score +6 in Reek's statement-counting algorithm:

def parse(arg, argv, &error)
  if !(val = arg) and (argv.empty? or /\A-/ =~ (val = argv[0]))
    return nil, block, nil                                         # +1
  end
  opt = (val = parse_arg(val, &error))[1]                          # +2
  val = conv_arg(*val)                                             # +3
  if opt and !arg
    argv.shift                                                     # +4
  else
    val[0] = nil                                                   # +5
  end
  val                                                              # +6
end

(You might argue that the two assigments within the first @if@ should count as statements, and that perhaps the nested assignment should count as +2.)

A Long Parameter List occurs when a method has a lot of parameters.

Example

Given

class Dummy
  def long_list(foo,bar,baz,fling,flung)
    puts foo,bar,baz,fling,flung
  end
end

Reek would report the following warning:

test.rb -- 1 warning:
  [2]:Dummy#long_list has 5 parameters (LongParameterList)

A common solution to this problem would be the introduction of parameter objects.

This cop checks for methods with too many parameters. The maximum number of parameters is configurable. Keyword arguments can optionally be excluded from the total count.

Cognitive Complexity

Cognitive Complexity is a measure of how difficult a unit of code is to intuitively understand. Unlike Cyclomatic Complexity, which determines how difficult your code will be to test, Cognitive Complexity tells you how difficult your code will be to read and comprehend.

A method's cognitive complexity is based on a few simple rules:

• Code is not considered more complex when it uses shorthand that the language provides for collapsing multiple statements into one
• Code is considered more complex for each "break in the linear flow of the code"
• Code is considered more complex when "flow breaking structures are nested"

Further reading

• Cognitive Complexity docs
• Cognitive Complexity: A new way of measuring understandability

Classes and modules are the units of reuse and release. It is therefore considered good practice to annotate every class and module with a brief comment outlining its responsibilities.

Example

Given

class Dummy
  # Do things...
end

Reek would emit the following warning:

test.rb -- 1 warning:
  [1]:Dummy has no descriptive comment (IrresponsibleModule)

Fixing this is simple - just an explaining comment:

# The Dummy class is responsible for ...
class Dummy
  # Do things...
end

Duplication occurs when two fragments of code look nearly identical, or when two fragments of code have nearly identical effects at some conceptual level.

Reek implements a check for Duplicate Method Call.

Example

Here's a very much simplified and contrived example. The following method will report a warning:

def double_thing()
  @other.thing + @other.thing
end

One quick approach to silence Reek would be to refactor the code thus:

def double_thing()
  thing = @other.thing
  thing + thing
end

A slightly different approach would be to replace all calls of double_thing by calls to @other.double_thing:

class Other
  def double_thing()
    thing + thing
  end
end

The approach you take will depend on balancing other factors in your code.

A Utility Function is any instance method that has no dependency on the state of the instance.

This cop checks for private or protected access modifiers which are applied to a singleton method. These access modifiers do not make singleton methods private/protected. private_class_method can be used for that.

Example:

# bad

class C
  private

  def self.method
    puts 'hi'
  end
end

Example:

# good

class C
  def self.method
    puts 'hi'
  end

  private_class_method :method
end

Example:

# good

class C
  class << self
    private

    def method
      puts 'hi'
    end
  end
end

This cop checks the length of lines in the source code. The maximum length is configurable. The tab size is configured in the IndentationWidth of the Layout/Tab cop.

This cop checks the length of lines in the source code. The maximum length is configurable. The tab size is configured in the IndentationWidth of the Layout/Tab cop.

This cop checks for private or protected access modifiers which are applied to a singleton method. These access modifiers do not make singleton methods private/protected. private_class_method can be used for that.

Example:

# bad

class C
  private

  def self.method
    puts 'hi'
  end
end

Example:

# good

class C
  def self.method
    puts 'hi'
  end

  private_class_method :method
end

Example:

# good

class C
  class << self
    private

    def method
      puts 'hi'
    end
  end
end

This cop checks the length of lines in the source code. The maximum length is configurable. The tab size is configured in the IndentationWidth of the Layout/Tab cop.

This cops checks for indentation that doesn't use the specified number of spaces.

See also the IndentationConsistency cop which is the companion to this one.

Example:

# bad
class A
 def test
  puts 'hello'
 end
end

# good
class A
  def test
    puts 'hello'
  end
end

Example: IgnoredPatterns: ['^\s*module']

# bad
module A
class B
  def test
  puts 'hello'
  end
end
end

# good
module A
class B
  def test
    puts 'hello'
  end
end
end

This cop checks for private or protected access modifiers which are applied to a singleton method. These access modifiers do not make singleton methods private/protected. private_class_method can be used for that.

Example:

# bad

class C
  private

  def self.method
    puts 'hi'
  end
end

Example:

# good

class C
  def self.method
    puts 'hi'
  end

  private_class_method :method
end

Example:

# good

class C
  class << self
    private

    def method
      puts 'hi'
    end
  end
end

This cop checks for private or protected access modifiers which are applied to a singleton method. These access modifiers do not make singleton methods private/protected. private_class_method can be used for that.

Example:

# bad

class C
  private

  def self.method
    puts 'hi'
  end
end

Example:

# good

class C
  def self.method
    puts 'hi'
  end

  private_class_method :method
end

Example:

# good

class C
  class << self
    private

    def method
      puts 'hi'
    end
  end
end

This cop checks for private or protected access modifiers which are applied to a singleton method. These access modifiers do not make singleton methods private/protected. private_class_method can be used for that.

Example:

# bad

class C
  private

  def self.method
    puts 'hi'
  end
end

Example:

# good

class C
  def self.method
    puts 'hi'
  end

  private_class_method :method
end

Example:

# good

class C
  class << self
    private

    def method
      puts 'hi'
    end
  end
end

This cop checks for redundant access modifiers, including those with no code, those which are repeated, and leading public modifiers in a class or module body. Conditionally-defined methods are considered as always being defined, and thus access modifiers guarding such methods are not redundant.

Example:

class Foo
  public # this is redundant (default access is public)

  def method
  end

  private # this is not redundant (a method is defined)
  def method2
  end

  private # this is redundant (no following methods are defined)
end

Example:

class Foo
  # The following is not redundant (conditionally defined methods are
  # considered as always defining a method)
  private

  if condition?
    def method
    end
  end

  protected # this is not redundant (method is defined)

  define_method(:method2) do
  end

  protected # this is redundant (repeated from previous modifier)

  [1,2,3].each do |i|
    define_method("foo#{i}") do
    end
  end

  # The following is redundant (methods defined on the class'
  # singleton class are not affected by the public modifier)
  public

  def self.method3
  end
end

Example:

# Lint/UselessAccessModifier:
#   ContextCreatingMethods:
#     - concerning
require 'active_support/concern'
class Foo
  concerning :Bar do
    def some_public_method
    end

    private

    def some_private_method
    end
  end

  # this is not redundant because `concerning` created its own context
  private

  def some_other_private_method
  end
end

Example:

# Lint/UselessAccessModifier:
#   MethodCreatingMethods:
#     - delegate
require 'active_support/core_ext/module/delegation'
class Foo
  # this is not redundant because `delegate` creates methods
  private

  delegate :method_a, to: :method_b
end

This cop checks the length of lines in the source code. The maximum length is configurable. The tab size is configured in the IndentationWidth of the Layout/Tab cop.

This cop checks method parameter names for how descriptive they are. It is highly configurable.

The MinNameLength config option takes an integer. It represents the minimum amount of characters the name must be. Its default is 3. The AllowNamesEndingInNumbers config option takes a boolean. When set to false, this cop will register offenses for names ending with numbers. Its default is false. The AllowedNames config option takes an array of whitelisted names that will never register an offense. The ForbiddenNames config option takes an array of blacklisted names that will always register an offense.

Example:

# bad
def bar(varOne, varTwo)
  varOne + varTwo
end

# With `AllowNamesEndingInNumbers` set to false
def foo(num1, num2)
  num1 * num2
end

# With `MinArgNameLength` set to number greater than 1
def baz(a, b, c)
  do_stuff(a, b, c)
end

# good
def bar(thud, fred)
  thud + fred
end

def foo(speed, distance)
  speed * distance
end

def baz(age_a, height_b, gender_c)
  do_stuff(age_a, height_b, gender_c)
end

This cop checks for private or protected access modifiers which are applied to a singleton method. These access modifiers do not make singleton methods private/protected. private_class_method can be used for that.

Example:

# bad

class C
  private

  def self.method
    puts 'hi'
  end
end

Example:

# good

class C
  def self.method
    puts 'hi'
  end

  private_class_method :method
end

Example:

# good

class C
  class << self
    private

    def method
      puts 'hi'
    end
  end
end

This cop checks the length of lines in the source code. The maximum length is configurable. The tab size is configured in the IndentationWidth of the Layout/Tab cop.

Checks for comma (,) not followed by some kind of space.

Example:

# bad
[1,2]
{ foo:bar,}

# good
[1, 2]
{ foo:bar, }

This cop checks the length of lines in the source code. The maximum length is configurable. The tab size is configured in the IndentationWidth of the Layout/Tab cop.

This cop checks method parameter names for how descriptive they are. It is highly configurable.

The MinNameLength config option takes an integer. It represents the minimum amount of characters the name must be. Its default is 3. The AllowNamesEndingInNumbers config option takes a boolean. When set to false, this cop will register offenses for names ending with numbers. Its default is false. The AllowedNames config option takes an array of whitelisted names that will never register an offense. The ForbiddenNames config option takes an array of blacklisted names that will always register an offense.

Example:

# bad
def bar(varOne, varTwo)
  varOne + varTwo
end

# With `AllowNamesEndingInNumbers` set to false
def foo(num1, num2)
  num1 * num2
end

# With `MinArgNameLength` set to number greater than 1
def baz(a, b, c)
  do_stuff(a, b, c)
end

# good
def bar(thud, fred)
  thud + fred
end

def foo(speed, distance)
  speed * distance
end

def baz(age_a, height_b, gender_c)
  do_stuff(age_a, height_b, gender_c)
end

This cop checks method parameter names for how descriptive they are. It is highly configurable.

The MinNameLength config option takes an integer. It represents the minimum amount of characters the name must be. Its default is 3. The AllowNamesEndingInNumbers config option takes a boolean. When set to false, this cop will register offenses for names ending with numbers. Its default is false. The AllowedNames config option takes an array of whitelisted names that will never register an offense. The ForbiddenNames config option takes an array of blacklisted names that will always register an offense.

Example:

# bad
def bar(varOne, varTwo)
  varOne + varTwo
end

# With `AllowNamesEndingInNumbers` set to false
def foo(num1, num2)
  num1 * num2
end

# With `MinArgNameLength` set to number greater than 1
def baz(a, b, c)
  do_stuff(a, b, c)
end

# good
def bar(thud, fred)
  thud + fred
end

def foo(speed, distance)
  speed * distance
end

def baz(age_a, height_b, gender_c)
  do_stuff(age_a, height_b, gender_c)
end

This cop checks method parameter names for how descriptive they are. It is highly configurable.

The MinNameLength config option takes an integer. It represents the minimum amount of characters the name must be. Its default is 3. The AllowNamesEndingInNumbers config option takes a boolean. When set to false, this cop will register offenses for names ending with numbers. Its default is false. The AllowedNames config option takes an array of whitelisted names that will never register an offense. The ForbiddenNames config option takes an array of blacklisted names that will always register an offense.

Example:

# bad
def bar(varOne, varTwo)
  varOne + varTwo
end

# With `AllowNamesEndingInNumbers` set to false
def foo(num1, num2)
  num1 * num2
end

# With `MinArgNameLength` set to number greater than 1
def baz(a, b, c)
  do_stuff(a, b, c)
end

# good
def bar(thud, fred)
  thud + fred
end

def foo(speed, distance)
  speed * distance
end

def baz(age_a, height_b, gender_c)
  do_stuff(age_a, height_b, gender_c)
end

This cop checks the length of lines in the source code. The maximum length is configurable. The tab size is configured in the IndentationWidth of the Layout/Tab cop.

This cop checks method parameter names for how descriptive they are. It is highly configurable.

The MinNameLength config option takes an integer. It represents the minimum amount of characters the name must be. Its default is 3. The AllowNamesEndingInNumbers config option takes a boolean. When set to false, this cop will register offenses for names ending with numbers. Its default is false. The AllowedNames config option takes an array of whitelisted names that will never register an offense. The ForbiddenNames config option takes an array of blacklisted names that will always register an offense.

Example:

# bad
def bar(varOne, varTwo)
  varOne + varTwo
end

# With `AllowNamesEndingInNumbers` set to false
def foo(num1, num2)
  num1 * num2
end

# With `MinArgNameLength` set to number greater than 1
def baz(a, b, c)
  do_stuff(a, b, c)
end

# good
def bar(thud, fred)
  thud + fred
end

def foo(speed, distance)
  speed * distance
end

def baz(age_a, height_b, gender_c)
  do_stuff(age_a, height_b, gender_c)
end

This cops checks for two or more consecutive blank lines.

Example:

# bad - It has two empty lines.
some_method
# one empty line
# two empty lines
some_method

# good
some_method
# one empty line
some_method

This cop checks the length of lines in the source code. The maximum length is configurable. The tab size is configured in the IndentationWidth of the Layout/Tab cop.

This cop checks for private or protected access modifiers which are applied to a singleton method. These access modifiers do not make singleton methods private/protected. private_class_method can be used for that.

Example:

# bad

class C
  private

  def self.method
    puts 'hi'
  end
end

Example:

# good

class C
  def self.method
    puts 'hi'
  end

  private_class_method :method
end

Example:

# good

class C
  class << self
    private

    def method
      puts 'hi'
    end
  end
end

This cop checks whether constant names are written using SCREAMINGSNAKECASE.

To avoid false positives, it ignores cases in which we cannot know for certain the type of value that would be assigned to a constant.

Example:

# bad
InchInCm = 2.54
INCHinCM = 2.54
Inch_In_Cm = 2.54

# good
INCH_IN_CM = 2.54

This cop checks the length of lines in the source code. The maximum length is configurable. The tab size is configured in the IndentationWidth of the Layout/Tab cop.

This cop checks the length of lines in the source code. The maximum length is configurable. The tab size is configured in the IndentationWidth of the Layout/Tab cop.

This cop checks the length of lines in the source code. The maximum length is configurable. The tab size is configured in the IndentationWidth of the Layout/Tab cop.

This cop checks method parameter names for how descriptive they are. It is highly configurable.

The MinNameLength config option takes an integer. It represents the minimum amount of characters the name must be. Its default is 3. The AllowNamesEndingInNumbers config option takes a boolean. When set to false, this cop will register offenses for names ending with numbers. Its default is false. The AllowedNames config option takes an array of whitelisted names that will never register an offense. The ForbiddenNames config option takes an array of blacklisted names that will always register an offense.

Example:

# bad
def bar(varOne, varTwo)
  varOne + varTwo
end

# With `AllowNamesEndingInNumbers` set to false
def foo(num1, num2)
  num1 * num2
end

# With `MinArgNameLength` set to number greater than 1
def baz(a, b, c)
  do_stuff(a, b, c)
end

# good
def bar(thud, fred)
  thud + fred
end

def foo(speed, distance)
  speed * distance
end

def baz(age_a, height_b, gender_c)
  do_stuff(age_a, height_b, gender_c)
end

This cop checks method parameter names for how descriptive they are. It is highly configurable.

The MinNameLength config option takes an integer. It represents the minimum amount of characters the name must be. Its default is 3. The AllowNamesEndingInNumbers config option takes a boolean. When set to false, this cop will register offenses for names ending with numbers. Its default is false. The AllowedNames config option takes an array of whitelisted names that will never register an offense. The ForbiddenNames config option takes an array of blacklisted names that will always register an offense.

Example:

# bad
def bar(varOne, varTwo)
  varOne + varTwo
end

# With `AllowNamesEndingInNumbers` set to false
def foo(num1, num2)
  num1 * num2
end

# With `MinArgNameLength` set to number greater than 1
def baz(a, b, c)
  do_stuff(a, b, c)
end

# good
def bar(thud, fred)
  thud + fred
end

def foo(speed, distance)
  speed * distance
end

def baz(age_a, height_b, gender_c)
  do_stuff(age_a, height_b, gender_c)
end

This cop checks for private or protected access modifiers which are applied to a singleton method. These access modifiers do not make singleton methods private/protected. private_class_method can be used for that.

Example:

# bad

class C
  private

  def self.method
    puts 'hi'
  end
end

Example:

# good

class C
  def self.method
    puts 'hi'
  end

  private_class_method :method
end

Example:

# good

class C
  class << self
    private

    def method
      puts 'hi'
    end
  end
end

This cop checks the length of lines in the source code. The maximum length is configurable. The tab size is configured in the IndentationWidth of the Layout/Tab cop.

Checks for comma (,) not followed by some kind of space.

Example:

# bad
[1,2]
{ foo:bar,}

# good
[1, 2]
{ foo:bar, }

This cop checks the length of lines in the source code. The maximum length is configurable. The tab size is configured in the IndentationWidth of the Layout/Tab cop.

This cop checks whether some constant value isn't a mutable literal (e.g. array or hash).

Example:

# bad
CONST = [1, 2, 3]

# good
CONST = [1, 2, 3].freeze

# good
CONST = <<~TESTING.freeze
This is a heredoc
TESTING

This cop can check for array literals made up of symbols that are not using the %i() syntax.

Alternatively, it checks for symbol arrays using the %i() syntax on projects which do not want to use that syntax.

Configuration option: MinSize If set, arrays with fewer elements than this value will not trigger the cop. For example, a MinSize of3` will not enforce a style on an array of 2 or fewer elements.

Example: EnforcedStyle: percent (default)

# good
%i[foo bar baz]

# bad
[:foo, :bar, :baz]

Example: EnforcedStyle: brackets

# good
[:foo, :bar, :baz]

# bad
%i[foo bar baz]

Use a guard clause instead of wrapping the code inside a conditional expression

Example:

# bad
def test
  if something
    work
  end
end

# good
def test
  return unless something
  work
end

# also good
def test
  work if something
end

# bad
if something
  raise 'exception'
else
  ok
end

# good
raise 'exception' if something
ok

This cop checks for missing top-level documentation of classes and modules. Classes with no body are exempt from the check and so are namespace modules - modules that have nothing in their bodies except classes, other modules, or constant definitions.

The documentation requirement is annulled if the class or module has a "#:nodoc:" comment next to it. Likewise, "#:nodoc: all" does the same for all its children.

Example:

# bad
class Person
  # ...
end

# good
# Description/Explanation of Person class
class Person
  # ...
end

Use a guard clause instead of wrapping the code inside a conditional expression

Example:

# bad
def test
  if something
    work
  end
end

# good
def test
  return unless something
  work
end

# also good
def test
  work if something
end

# bad
if something
  raise 'exception'
else
  ok
end

# good
raise 'exception' if something
ok

This cop checks the style of children definitions at classes and modules. Basically there are two different styles:

Example: EnforcedStyle: nested (default)

# good
# have each child on its own line
class Foo
  class Bar
  end
end

Example: EnforcedStyle: compact

# good
# combine definitions as much as possible
class Foo::Bar
end

The compact style is only forced for classes/modules with one child.