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 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 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 tries to produce a complexity score that's a measure of the complexity the reader experiences when looking at a method. For that reason it considers when nodes as something that doesn't add as much complexity as an if or a &&. Except if it's one of those special case/when constructs where there's no expression after case. Then the cop treats it as an if/elsif/elsif... and lets all the when nodes count. In contrast to the CyclomaticComplexity cop, this cop considers else nodes as adding complexity.

Example:

def my_method                   # 1
  if cond                       # 1
    case var                    # 2 (0.8 + 4 * 0.2, rounded)
    when 1 then func_one
    when 2 then func_two
    when 3 then func_three
    when 4..10 then func_other
    end
  else                          # 1
    do_something until a && b   # 2
  end                           # ===
end                             # 7 complexity points

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 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 the case equality operator(===).

Example:

# bad
Array === something
(1..100) === 7
/something/ === some_string

# good
something.is_a?(Array)
(1..100).include?(7)
some_string =~ /something/

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 non-ascii (non-English) characters in comments. You could set an array of allowed non-ascii chars in AllowedChars attribute (empty by default).

Example:

# bad
# Translates from English to 日本語。

# good
# Translates from English to Japanese

This cop checks for uses of the case equality operator(===).

Example:

# bad
Array === something
(1..100) === 7
/something/ === some_string

# good
something.is_a?(Array)
(1..100).include?(7)
some_string =~ /something/

This cop checks for unparenthesized method calls in the argument list of a parenthesized method call.

Example:

# good
method1(method2(arg), method3(arg))

# bad
method1(method2 arg, method3, arg)

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 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 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 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

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

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 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