Size and Complexity Rules (“rulesets/size.xml”)

AbcMetric Rule

Calculates the ABC size metric for methods/classes and checks against configured threshold values.

The maxMethodAbcScore property holds the threshold value for the ABC score for each method. If this value is non-zero, a method with an ABC score greater than this value is considered a violation. The value does not have to be an integer (e.g., 1.7 is allowed).

The maxClassAverageMethodAbcScore property holds the threshold value for the average ABC score for each class. If this value is non-zero, a class with an average ABC score value greater than this value is considered a violation. The value does not have to be an integer.

The maxClassAbcScore property holds the threshold value for the total ABC score value for each class. If this value is non-zero, a class with a total ABC score greater than this value is considered a violation. The value does not have to be an integer.

This rule treats “closure fields” as methods. If a class field is initialized to a Closure (ClosureExpression), then that Closure is analyzed and checked just like a method.

ABC Size Metric Calculation Rules

The ABC score is calculated as follows: The ABC metric measures size by counting the number of Assignments (A), Branches (B) and Conditions (C) and assigns a single numerical score calculated as:

The ABC Metric calculation rules for Groovy:

• Add one to the assignment count for each occurrence of an assignment operator, excluding constant declarations: = *= /= %= += **= **= &= |= ^= `=
• Add one to the assignment count for each occurrence of an increment or decrement operator (prefix or postfix): ++ –
• Add one to the branch count for each function call or class method call.
• Add one to the branch count for each occurrence of the new operator.
• Add one to the condition count for each use of a conditional operator: == != = *= * * *= =~ ==~
• Add one to the condition count for each use of the following keywords: else case default try catch ?
• Add one to the condition count for each unary conditional expression.

Notes

• See the ABC Metric specification
• See the Blog post describing guidelines for interpreting an ABC score
• This (Spanish) blog post about the eXcentia Sonar ABC Metric Plugin (for Java) includes a table of risk classifications for ABC scores for both methods and classes.
• See the GMetrics ABC metric. This includes a discussion of guidelines for interpreting ABC scores.
• This rule requires the GMetrics jar on the classpath. See GMetrics.

ClassSize Rule

Checks if the size of a class exceeds the number of lines specified by the maxLines property.

CrapMetric Rule

Calculates the C.R.A.P. (Change Risk Anti-Patterns) metric score for methods/classes and checks against configured threshold values.

The CRAP metric score is based on the cyclomatic complexity and test coverage for individual methods. A method with a CRAP value greater than the maxMethodCrapScore property causes a violation. Likewise, a class that has an (average method) CRAP value greater than the maxClassAverageMethodCrapScore property causes a violation.

NOTE: This rule requires the GMetrics[3] jar, version 0.5 (or later), on the classpath, as well as a Cobertura[4]-[6] XML coverage file. If either of these prerequisites is not available, this rule logs a warning messages and exits (i.e., does nothing).

The maxMethodCrapScore property holds the threshold value for the CRAP value for each method. If this value is non-zero, a method with a cyclomatic complexity value greater than this value is considered a violation.

The maxClassAverageMethodCrapScore property holds the threshold value for the average CRAP value for each class. If this value is non-zero, a class with an average cyclomatic complexity value greater than this value is considered a violation.

NOTE: This rule does NOT treat closure fields as methods (unlike some of the other size/complexity rules).

CRAP Formula

Given a Groovy method m, C.R.A.P. for m is calculated as follows:

  C.R.A.P.(m) = comp(m)^2 * (1 - cov(m)/100)^3 + comp(m)

Where comp(m) is the cyclomatic complexity of method m, and cov(m) is the test code coverage provided by automated tests.

References

• [1] The original 2007 blog post that defined the CRAP metric.

• [2] A 2011 blog post from Alberto Savoia (the co-creator of the CRAP metric with Bob Evans), describing the formula, the motivation, and the CRAP4J tool for calculating CRAP score for Java code.

• [3] The GMetrics CRAP Metric.

• [4] Cobertura – Cobertura is a free Java tool that calculates the percentage of code accessed by tests. It can be used to identify which parts of your Java program are lacking test coverage.

• [5] Cobertura Ant Task Reference

• [6] Cobertura Maven Plugin

CyclomaticComplexity Rule

Calculates the Cyclomatic Complexity for methods/classes and checks against configured threshold values.

The maxMethodComplexity property holds the threshold value for the cyclomatic complexity value for each method. If this value is non-zero, a method with a cyclomatic complexity value greater than this value is considered a violation.

The maxClassAverageMethodComplexity property holds the threshold value for the average cyclomatic complexity value for each class. If this value is non-zero, a class with an average cyclomatic complexity value greater than this value is considered a violation.

This rule treats “closure fields” as methods. If a class field is initialized to a Closure (ClosureExpression), then that Closure is analyzed and checked just like a method.

Cyclomatic Complexity Metric Calculation Rules

The cyclomatic complexity value is calculated as follows:

Start with a initial (default) value of one (1). Add one (1) for each occurrence of each of the following:

 * `if` statement

 * `while` statement

 * `for` statement

 * `case` statement

 * `catch` statement

 * `&&` and `||` boolean operations

 * `?:` ternary operator and `?:` *Elvis* operator.

 * `?.` null-check operator

Notes

• See the Cyclomatic Complexity Wikipedia entry
• See the original paper describing Cyclomatic Complexity
• See the GMetrics Cyclomatic Complexity metric. This includes a discussion of guidelines for interpreting cyclomatic complexity values.
• This rule requires the GMetrics jar on the classpath. See GMetrics.

MethodCount Rule

Since CodeNarc 0.11

Checks if the number of methods within a class exceeds the number of lines specified by the maxMethod property.

A class with too many methods is probably a good suspect for refactoring, in order to reduce its complexity and find a way to have more fine grained objects.

MethodSize Rule

Checks if the size of a method exceeds the number of lines specified by the maxLines property.

Known Limitations:

• Annotations on a method are included in the size (line count) for that method.

NestedBlockDepth Rule

Checks for blocks or closures nested more deeply than a configured maximum number. Blocks include if, for, while, switch, try, catch, finally and synchronized blocks/statements, as well as closures.

Methods calls, constructor calls, and property access through Builder objects are ignore. For instance, this code does not cause a violation:

    myBuilder.root {
        foo {
            bar {
                baz {
                    quix {
                        qux {
                            quaxz {
                            }
                        }
                    }
                }
            }
        }
    }

ParameterCount Rule

Since CodeNarc 0.23

Checks if the number of parameters in method/constructor exceeds the number of parameters specified by the maxParameters property.

Example of violations:

    void someMethod(int arg1, int arg2, int arg3, int arg4, int arg5, int arg6) { // violation
    }

    @Override
    void someMethod(int arg1, int arg2, int arg3, int arg4, int arg5, int arg6, int arg7) { // no violation if ignoreOverriddenMethods == true
    }

    class SampleClass {
        SampleClass(int arg1, int arg2, int arg3, int arg4, int arg5, int arg6, int arg7) { // violation
        }
    }