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cops_metrics.md

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Metrics

Metrics/AbcSize

Enabled by default Safe Supports autocorrection VersionAdded VersionChanged
Enabled Yes No 0.27 0.81

This cop checks that the ABC size of methods is not higher than the configured maximum. The ABC size is based on assignments, branches (method calls), and conditions. See http://c2.com/cgi/wiki?AbcMetric and https://en.wikipedia.org/wiki/ABC_Software_Metric.

Configurable attributes

Name Default value Configurable values
IgnoredMethods [] Array
Max 15 Integer

References

Metrics/BlockLength

Enabled by default Safe Supports autocorrection VersionAdded VersionChanged
Enabled Yes No 0.44 0.66

This cop checks if the length of a block exceeds some maximum value. Comment lines can optionally be ignored. The maximum allowed length is configurable. The cop can be configured to ignore blocks passed to certain methods.

Configurable attributes

Name Default value Configurable values
CountComments false Boolean
Max 25 Integer
ExcludedMethods refine Array
Exclude **/*.gemspec Array

Metrics/BlockNesting

Enabled by default Safe Supports autocorrection VersionAdded VersionChanged
Enabled Yes No 0.25 0.47

This cop checks for excessive nesting of conditional and looping constructs.

You can configure if blocks are considered using the CountBlocks option. When set to false (the default) blocks are not counted towards the nesting level. Set to true to count blocks as well.

The maximum level of nesting allowed is configurable.

Configurable attributes

Name Default value Configurable values
CountBlocks false Boolean
Max 3 Integer

References

Metrics/ClassLength

Enabled by default Safe Supports autocorrection VersionAdded VersionChanged
Enabled Yes No 0.25 -

This cop checks if the length a class exceeds some maximum value. Comment lines can optionally be ignored. The maximum allowed length is configurable.

Configurable attributes

Name Default value Configurable values
CountComments false Boolean
Max 100 Integer

Metrics/CyclomaticComplexity

Enabled by default Safe Supports autocorrection VersionAdded VersionChanged
Enabled Yes No 0.25 0.81

This cop checks that the cyclomatic complexity of methods is not higher than the configured maximum. The cyclomatic complexity is the number of linearly independent paths through a method. The algorithm counts decision points and adds one.

An if statement (or unless or ?:) increases the complexity by one. An else branch does not, since it doesn't add a decision point. The && operator (or keyword and) can be converted to a nested if statement, and ||/or is shorthand for a sequence of ifs, so they also add one. Loops can be said to have an exit condition, so they add one.

Configurable attributes

Name Default value Configurable values
IgnoredMethods [] Array
Max 6 Integer

Metrics/MethodLength

Enabled by default Safe Supports autocorrection VersionAdded VersionChanged
Enabled Yes No 0.25 0.59.2

This cop checks if the length of a method exceeds some maximum value. Comment lines can optionally be ignored. The maximum allowed length is configurable.

Configurable attributes

Name Default value Configurable values
CountComments false Boolean
Max 10 Integer
ExcludedMethods [] Array

References

Metrics/ModuleLength

Enabled by default Safe Supports autocorrection VersionAdded VersionChanged
Enabled Yes No 0.31 -

This cop checks if the length a module exceeds some maximum value. Comment lines can optionally be ignored. The maximum allowed length is configurable.

Configurable attributes

Name Default value Configurable values
CountComments false Boolean
Max 100 Integer

Metrics/ParameterLists

Enabled by default Safe Supports autocorrection VersionAdded VersionChanged
Enabled Yes No 0.25 -

This cop checks for methods with too many parameters. The maximum number of parameters is configurable. Keyword arguments can optionally be excluded from the total count.

Configurable attributes

Name Default value Configurable values
Max 5 Integer
CountKeywordArgs true Boolean

References

Metrics/PerceivedComplexity

Enabled by default Safe Supports autocorrection VersionAdded VersionChanged
Enabled Yes No 0.25 0.81

This cop tries to produce a complexity score that's a measure of the complexity the reader experiences when looking at a method. For that reason it considers when nodes as something that doesn't add as much complexity as an if or a &&. Except if it's one of those special case/when constructs where there's no expression after case. Then the cop treats it as an if/elsif/elsif... and lets all the when nodes count. In contrast to the CyclomaticComplexity cop, this cop considers else nodes as adding complexity.

Examples

def my_method                   # 1
  if cond                       # 1
    case var                    # 2 (0.8 + 4 * 0.2, rounded)
    when 1 then func_one
    when 2 then func_two
    when 3 then func_three
    when 4..10 then func_other
    end
  else                          # 1
    do_something until a && b   # 2
  end                           # ===
end                             # 7 complexity points

Configurable attributes

Name Default value Configurable values
IgnoredMethods [] Array
Max 7 Integer