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.

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.

This cop checks that the ABC size of methods is not higher than the configured maximum. The ABC size is based on assignments, branches (method calls), and conditions. See http://c2.com/cgi/wiki?AbcMetric

This cop checks that the cyclomatic complexity of methods is not higher than the configured maximum. The cyclomatic complexity is the number of linearly independent paths through a method. The algorithm counts decision points and adds one.

An if statement (or unless or ?:) increases the complexity by one. An else branch does not, since it doesn't add a decision point. The && operator (or keyword and) can be converted to a nested if statement, and ||/or is shorthand for a sequence of ifs, so they also add one. Loops can be said to have an exit condition, so they add one.

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.

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

This cop checks that the cyclomatic complexity of methods is not higher than the configured maximum. The cyclomatic complexity is the number of linearly independent paths through a method. The algorithm counts decision points and adds one.

An if statement (or unless or ?:) increases the complexity by one. An else branch does not, since it doesn't add a decision point. The && operator (or keyword and) can be converted to a nested if statement, and ||/or is shorthand for a sequence of ifs, so they also add one. Loops can be said to have an exit condition, so they add one.

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

Duplicated Code

Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:

Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.

When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).

Tuning

This issue has a mass of 48.

We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.

The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.

If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.

See codeclimate-duplication's documentation for more information about tuning the mass threshold in your .codeclimate.yml.

Refactorings

• Extract Method
• Extract Class
• Form Template Method
• Introduce Null Object
• Pull Up Method
• Pull Up Field
• Substitute Algorithm

Further Reading

• Don't Repeat Yourself on the C2 Wiki
• Duplicated Code on SourceMaking
• Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76

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

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 whether the end keywords are aligned properly.

Three modes are supported through the EnforcedStyleAlignWith configuration parameter:

If it's set to keyword (which is the default), the end shall be aligned with the start of the keyword (if, class, etc.).

If it's set to variable the end shall be aligned with the left-hand-side of the variable assignment, if there is one.

If it's set to start_of_line, the end shall be aligned with the start of the line where the matching keyword appears.

Example: EnforcedStyleAlignWith: keyword (default)

# bad

variable = if true
    end

# good

variable = if true
           end

Example: EnforcedStyleAlignWith: variable

# bad

variable = if true
    end

# good

variable = if true
end

Example: EnforcedStyleAlignWith: startofline

# bad

variable = if true
    end

# good

puts(if true
end)

This cop checks how the whens of a case expression are indented in relation to its case or end keyword.

It will register a separate offense for each misaligned when.

Example:

# If Layout/EndAlignment is set to keyword style (default)
# *case* and *end* should always be aligned to same depth,
# and therefore *when* should always be aligned to both -
# regardless of configuration.

# bad for all styles
case n
  when 0
    x * 2
  else
    y / 3
end

# good for all styles
case n
when 0
  x * 2
else
  y / 3
end

Example: EnforcedStyle: case (default)

# if EndAlignment is set to other style such as
# start_of_line (as shown below), then *when* alignment
# configuration does have an effect.

# bad
a = case n
when 0
  x * 2
else
  y / 3
end

# good
a = case n
    when 0
      x * 2
    else
      y / 3
end

Example: EnforcedStyle: end

# bad
a = case n
    when 0
      x * 2
    else
      y / 3
end

# good
a = case n
when 0
  x * 2
else
  y / 3
end

Access modifiers should be surrounded by blank lines.

Example:

# bad
class Foo
  def bar; end
  private
  def baz; end
end

# good
class Foo
  def bar; end

  private

  def baz; end
end

This cop checks how the whens of a case expression are indented in relation to its case or end keyword.

It will register a separate offense for each misaligned when.

Example:

# If Layout/EndAlignment is set to keyword style (default)
# *case* and *end* should always be aligned to same depth,
# and therefore *when* should always be aligned to both -
# regardless of configuration.

# bad for all styles
case n
  when 0
    x * 2
  else
    y / 3
end

# good for all styles
case n
when 0
  x * 2
else
  y / 3
end

Example: EnforcedStyle: case (default)

# if EndAlignment is set to other style such as
# start_of_line (as shown below), then *when* alignment
# configuration does have an effect.

# bad
a = case n
when 0
  x * 2
else
  y / 3
end

# good
a = case n
    when 0
      x * 2
    else
      y / 3
end

Example: EnforcedStyle: end

# bad
a = case n
    when 0
      x * 2
    else
      y / 3
end

# good
a = case n
when 0
  x * 2
else
  y / 3
end

This cop checks whether the end keywords are aligned properly.

Three modes are supported through the EnforcedStyleAlignWith configuration parameter:

If it's set to keyword (which is the default), the end shall be aligned with the start of the keyword (if, class, etc.).

If it's set to variable the end shall be aligned with the left-hand-side of the variable assignment, if there is one.

If it's set to start_of_line, the end shall be aligned with the start of the line where the matching keyword appears.

Example: EnforcedStyleAlignWith: keyword (default)

# bad

variable = if true
    end

# good

variable = if true
           end

Example: EnforcedStyleAlignWith: variable

# bad

variable = if true
    end

# good

variable = if true
end

Example: EnforcedStyleAlignWith: startofline

# bad

variable = if true
    end

# good

puts(if true
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

Modifiers should be indented as deep as method definitions, or as deep as the class/module keyword, depending on configuration.

Example: EnforcedStyle: indent (default)

# bad
class Plumbus
private
  def smooth; end
end

# good
class Plumbus
  private
  def smooth; end
end

Example: EnforcedStyle: outdent

# bad
class Plumbus
  private
  def smooth; end
end

# good
class Plumbus
private
  def smooth; end
end

This cop checks how the whens of a case expression are indented in relation to its case or end keyword.

It will register a separate offense for each misaligned when.

Example:

# If Layout/EndAlignment is set to keyword style (default)
# *case* and *end* should always be aligned to same depth,
# and therefore *when* should always be aligned to both -
# regardless of configuration.

# bad for all styles
case n
  when 0
    x * 2
  else
    y / 3
end

# good for all styles
case n
when 0
  x * 2
else
  y / 3
end

Example: EnforcedStyle: case (default)

# if EndAlignment is set to other style such as
# start_of_line (as shown below), then *when* alignment
# configuration does have an effect.

# bad
a = case n
when 0
  x * 2
else
  y / 3
end

# good
a = case n
    when 0
      x * 2
    else
      y / 3
end

Example: EnforcedStyle: end

# bad
a = case n
    when 0
      x * 2
    else
      y / 3
end

# good
a = case n
when 0
  x * 2
else
  y / 3
end

This cop checks how the whens of a case expression are indented in relation to its case or end keyword.

It will register a separate offense for each misaligned when.

Example:

# If Layout/EndAlignment is set to keyword style (default)
# *case* and *end* should always be aligned to same depth,
# and therefore *when* should always be aligned to both -
# regardless of configuration.

# bad for all styles
case n
  when 0
    x * 2
  else
    y / 3
end

# good for all styles
case n
when 0
  x * 2
else
  y / 3
end

Example: EnforcedStyle: case (default)

# if EndAlignment is set to other style such as
# start_of_line (as shown below), then *when* alignment
# configuration does have an effect.

# bad
a = case n
when 0
  x * 2
else
  y / 3
end

# good
a = case n
    when 0
      x * 2
    else
      y / 3
end

Example: EnforcedStyle: end

# bad
a = case n
    when 0
      x * 2
    else
      y / 3
end

# good
a = case n
when 0
  x * 2
else
  y / 3
end

This cop checks how the whens of a case expression are indented in relation to its case or end keyword.

It will register a separate offense for each misaligned when.

Example:

# If Layout/EndAlignment is set to keyword style (default)
# *case* and *end* should always be aligned to same depth,
# and therefore *when* should always be aligned to both -
# regardless of configuration.

# bad for all styles
case n
  when 0
    x * 2
  else
    y / 3
end

# good for all styles
case n
when 0
  x * 2
else
  y / 3
end

Example: EnforcedStyle: case (default)

# if EndAlignment is set to other style such as
# start_of_line (as shown below), then *when* alignment
# configuration does have an effect.

# bad
a = case n
when 0
  x * 2
else
  y / 3
end

# good
a = case n
    when 0
      x * 2
    else
      y / 3
end

Example: EnforcedStyle: end

# bad
a = case n
    when 0
      x * 2
    else
      y / 3
end

# good
a = case n
when 0
  x * 2
else
  y / 3
end

This cop checks how the whens of a case expression are indented in relation to its case or end keyword.

It will register a separate offense for each misaligned when.

Example:

# If Layout/EndAlignment is set to keyword style (default)
# *case* and *end* should always be aligned to same depth,
# and therefore *when* should always be aligned to both -
# regardless of configuration.

# bad for all styles
case n
  when 0
    x * 2
  else
    y / 3
end

# good for all styles
case n
when 0
  x * 2
else
  y / 3
end

Example: EnforcedStyle: case (default)

# if EndAlignment is set to other style such as
# start_of_line (as shown below), then *when* alignment
# configuration does have an effect.

# bad
a = case n
when 0
  x * 2
else
  y / 3
end

# good
a = case n
    when 0
      x * 2
    else
      y / 3
end

Example: EnforcedStyle: end

# bad
a = case n
    when 0
      x * 2
    else
      y / 3
end

# good
a = case n
when 0
  x * 2
else
  y / 3
end

This cop checks how the whens of a case expression are indented in relation to its case or end keyword.

It will register a separate offense for each misaligned when.

Example:

# If Layout/EndAlignment is set to keyword style (default)
# *case* and *end* should always be aligned to same depth,
# and therefore *when* should always be aligned to both -
# regardless of configuration.

# bad for all styles
case n
  when 0
    x * 2
  else
    y / 3
end

# good for all styles
case n
when 0
  x * 2
else
  y / 3
end

Example: EnforcedStyle: case (default)

# if EndAlignment is set to other style such as
# start_of_line (as shown below), then *when* alignment
# configuration does have an effect.

# bad
a = case n
when 0
  x * 2
else
  y / 3
end

# good
a = case n
    when 0
      x * 2
    else
      y / 3
end

Example: EnforcedStyle: end

# bad
a = case n
    when 0
      x * 2
    else
      y / 3
end

# good
a = case n
when 0
  x * 2
else
  y / 3
end

Checks if uses of quotes match the configured preference.

Example: EnforcedStyle: single_quotes (default)

# bad
"No special symbols"
"No string interpolation"
"Just text"

# good
'No special symbols'
'No string interpolation'
'Just text'
"Wait! What's #{this}!"

Example: EnforcedStyle: double_quotes

# bad
'Just some text'
'No special chars or interpolation'

# good
"Just some text"
"No special chars or interpolation"
"Every string in #{project} uses double_quotes"

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 how the whens of a case expression are indented in relation to its case or end keyword.

It will register a separate offense for each misaligned when.

Example:

# If Layout/EndAlignment is set to keyword style (default)
# *case* and *end* should always be aligned to same depth,
# and therefore *when* should always be aligned to both -
# regardless of configuration.

# bad for all styles
case n
  when 0
    x * 2
  else
    y / 3
end

# good for all styles
case n
when 0
  x * 2
else
  y / 3
end

Example: EnforcedStyle: case (default)

# if EndAlignment is set to other style such as
# start_of_line (as shown below), then *when* alignment
# configuration does have an effect.

# bad
a = case n
when 0
  x * 2
else
  y / 3
end

# good
a = case n
    when 0
      x * 2
    else
      y / 3
end

Example: EnforcedStyle: end

# bad
a = case n
    when 0
      x * 2
    else
      y / 3
end

# good
a = case n
when 0
  x * 2
else
  y / 3
end

This cop checks whether the end keywords are aligned properly.

Three modes are supported through the EnforcedStyleAlignWith configuration parameter:

If it's set to keyword (which is the default), the end shall be aligned with the start of the keyword (if, class, etc.).

If it's set to variable the end shall be aligned with the left-hand-side of the variable assignment, if there is one.

If it's set to start_of_line, the end shall be aligned with the start of the line where the matching keyword appears.

Example: EnforcedStyleAlignWith: keyword (default)

# bad

variable = if true
    end

# good

variable = if true
           end

Example: EnforcedStyleAlignWith: variable

# bad

variable = if true
    end

# good

variable = if true
end

Example: EnforcedStyleAlignWith: startofline

# bad

variable = if true
    end

# good

puts(if true
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 methods invoked via the :: operator instead of the . operator (like FileUtils::rmdir instead of FileUtils.rmdir).

Example:

# bad
Timeout::timeout(500) { do_something }
FileUtils::rmdir(dir)
Marshal::dump(obj)

# good
Timeout.timeout(500) { do_something }
FileUtils.rmdir(dir)
Marshal.dump(obj)

This cop checks for methods invoked via the :: operator instead of the . operator (like FileUtils::rmdir instead of FileUtils.rmdir).

Example:

# bad
Timeout::timeout(500) { do_something }
FileUtils::rmdir(dir)
Marshal::dump(obj)

# good
Timeout.timeout(500) { do_something }
FileUtils.rmdir(dir)
Marshal.dump(obj)

This cop checks how the whens of a case expression are indented in relation to its case or end keyword.

It will register a separate offense for each misaligned when.

Example:

# If Layout/EndAlignment is set to keyword style (default)
# *case* and *end* should always be aligned to same depth,
# and therefore *when* should always be aligned to both -
# regardless of configuration.

# bad for all styles
case n
  when 0
    x * 2
  else
    y / 3
end

# good for all styles
case n
when 0
  x * 2
else
  y / 3
end

Example: EnforcedStyle: case (default)

# if EndAlignment is set to other style such as
# start_of_line (as shown below), then *when* alignment
# configuration does have an effect.

# bad
a = case n
when 0
  x * 2
else
  y / 3
end

# good
a = case n
    when 0
      x * 2
    else
      y / 3
end

Example: EnforcedStyle: end

# bad
a = case n
    when 0
      x * 2
    else
      y / 3
end

# good
a = case n
when 0
  x * 2
else
  y / 3
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 how the whens of a case expression are indented in relation to its case or end keyword.

It will register a separate offense for each misaligned when.

Example:

# If Layout/EndAlignment is set to keyword style (default)
# *case* and *end* should always be aligned to same depth,
# and therefore *when* should always be aligned to both -
# regardless of configuration.

# bad for all styles
case n
  when 0
    x * 2
  else
    y / 3
end

# good for all styles
case n
when 0
  x * 2
else
  y / 3
end

Example: EnforcedStyle: case (default)

# if EndAlignment is set to other style such as
# start_of_line (as shown below), then *when* alignment
# configuration does have an effect.

# bad
a = case n
when 0
  x * 2
else
  y / 3
end

# good
a = case n
    when 0
      x * 2
    else
      y / 3
end

Example: EnforcedStyle: end

# bad
a = case n
    when 0
      x * 2
    else
      y / 3
end

# good
a = case n
when 0
  x * 2
else
  y / 3
end

This cop checks for uses of and and or, and suggests using && and || instead. It can be configured to check only in conditions, or in all contexts.

Example: EnforcedStyle: always (default)

# bad
foo.save and return

# bad
if foo and bar
end

# good
foo.save && return

# good
if foo && bar
end

Example: EnforcedStyle: conditionals

# bad
if foo and bar
end

# good
foo.save && return

# good
foo.save and return

# good
if foo && bar
end

This cops checks the alignment of else keywords. Normally they should be aligned with an if/unless/while/until/begin/def keyword, but there are special cases when they should follow the same rules as the alignment of end.

Example:

# bad
if something
  code
 else
  code
end

# bad
if something
  code
 elsif something
  code
end

# good
if something
  code
else
  code
end

This cop checks for methods invoked via the :: operator instead of the . operator (like FileUtils::rmdir instead of FileUtils.rmdir).

Example:

# bad
Timeout::timeout(500) { do_something }
FileUtils::rmdir(dir)
Marshal::dump(obj)

# good
Timeout.timeout(500) { do_something }
FileUtils.rmdir(dir)
Marshal.dump(obj)