Cyclomatic Complexity

Number of linearly independent paths through a block of code. Conditional operators or loops increase the number of paths in a code. The more paths, the higher the number of test cases that need to be implemented. The metric complies with McCabe's original definition:

• methods have a base complexity of 1.
• every control flow statement (if, catch, throw, do, while, for, break, continue) and conditional expression (? ... : ...) increases complexity
• else, finally and default don't count
• some operators like &&, ||, ?., ...?, ?? and ??= also increase complexity

Config example

dart_code_metrics:
  ...
  metrics:
    ...
    cyclomatic-complexity: 20
    ...

Example

void visitBlock(Token firstToken, Token lastToken) {
  const tokenTypes = [
    TokenType.AMPERSAND_AMPERSAND,
    TokenType.BAR_BAR,
    TokenType.QUESTION_PERIOD,
    TokenType.QUESTION_QUESTION,
    TokenType.QUESTION_QUESTION_EQ,
  ];

  var token = firstToken;
  while (token != lastToken) {
    if (token.matchesAny(tokenTypes)) {
      _increaseComplexity(token);
    }

    token = token.next;
  }
}

Cyclomatic Complexity for the example function is 3.