DeepSource

A function with high cyclomatic complexity can be hard to understand and maintain. Cyclomatic complexity is a software metric that measures the number of independent paths through a function. A higher cyclomatic complexity indicates that the function has more decision points and is more complex.

Functions with high cyclomatic complexity are more likely to have bugs and be harder to test. They may lead to reduced code maintainability and increased development time.

To reduce the cyclomatic complexity of a function, you can:

Break the function into smaller, more manageable functions.
Refactor complex logic into separate functions or classes.
Avoid multiple return paths and deeply nested control expressions.

Bad practice

def complex_function(a, b, c, d, e)
  if a > 10
    case b
    when 1
      if c == :foo
        while d < 100
          if e != :bar
            case d % 3
            when 0
              puts "Case 0"
            when 1
              puts "Case 1"
            else
              puts "Case 2"
            end
            d += 1
          end
        end
      else
        puts "Option A"
      end
    when 2
      if c == :baz
        for i in 0..5
          unless i == 3
            puts "Loop iteration #{i}"
          end
        end
      else
        puts "Option B"
      end
    else
      puts "Option C"
    end
  else
    puts "Less than or equal to 10"
  end
end

def complex_function(a, b, c, d, e)
  if a > 10
    handle_case_b(a, b, c, d, e)
  else
    puts "Less than or equal to 10"
  end
end

def handle_case_b(a, b, c, d, e)
  case b
  when 1
    handle_case_1(c, d, e)
  when 2
    handle_case_2(c)
  else
    puts "Option C"
  end
end

def handle_case_1(c, d, e)
  if c == :foo
    perform_while_loop(d, e)
  else
    puts "Option A"
  end
end

def perform_while_loop(d, e)
  while d < 100
    unless e == :bar
      handle_case_d_mod(d)
      d += 1
    end
  end
end

def handle_case_d_mod(d)
  case d % 3
  when 0
    puts "Case 0"
  when 1
    puts "Case 1"
  else
    puts "Case 2"
  end
end

def handle_case_2(c)
  if c == :baz
    perform_for_loop
  else
    puts "Option B"
  end
end

def perform_for_loop
  (0..5).each do |i|
    unless i == 3
      puts "Loop iteration #{i}"
    end
  end
end

Issue configuration

Cyclomatic complexity threshold can be configured using the cyclomatic_complexity_threshold meta field in the .deepsource.toml config file.

Configuring this is optional. If you don't provide a value, the Analyzer will raise issues for functions with complexity higher than the default threshold, which is medium(it's raised only for complexity greater than 15) for the Ruby Analyzer.

Here's the mapping of the risk category to the cyclomatic complexity score to help you configure this better:

Risk category	Cyclomatic complexity range	Recommended action
low	1-5	No action needed.
medium	6-15	Review and monitor.
high	16-25	Review and refactor. Recommended to add comments if the function is absolutely needed to be kept as it is.
very-high	26-50	Refactor to reduce the complexity.
critical	>50	Must refactor this. This can make the code untestable and very difficult to understand.

Ruby

Function with cyclomatic complexity higher than threshold RB-R1001

Bad practice

Recommended

Issue configuration