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 for duplicated instance (or singleton) method definitions.

Example:

# bad

def duplicated
  1
end

def duplicated
  2
end

Example:

# bad

def duplicated
  1
end

alias duplicated other_duplicated

Example:

# good

def duplicated
  1
end

def other_duplicated
  2
end