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 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

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 31.

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

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 31.

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

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 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)

If the else branch of a conditional consists solely of an if node, it can be combined with the else to become an elsif. This helps to keep the nesting level from getting too deep.

Example:

# bad
if condition_a
  action_a
else
  if condition_b
    action_b
  else
    action_c
  end
end

# good
if condition_a
  action_a
elsif condition_b
  action_b
else
  action_c
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)