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Cyclomatic Complexity

Number of linearly independent paths through a block of code. Conditional operators or loops increases 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 (? ... : ...) increase 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.