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

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.

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.

Cognitive Complexity

Cognitive Complexity is a measure of how difficult a unit of code is to intuitively understand. Unlike Cyclomatic Complexity, which determines how difficult your code will be to test, Cognitive Complexity tells you how difficult your code will be to read and comprehend.

A method's cognitive complexity is based on a few simple rules:

• Code is not considered more complex when it uses shorthand that the language provides for collapsing multiple statements into one
• Code is considered more complex for each "break in the linear flow of the code"
• Code is considered more complex when "flow breaking structures are nested"

Further reading

• Cognitive Complexity docs
• Cognitive Complexity: A new way of measuring understandability

Duplicated Code

Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:

Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.

When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).

Tuning

This issue has a mass of 38.

We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.

The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.

If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.

See codeclimate-duplication's documentation for more information about tuning the mass threshold in your .codeclimate.yml.

Refactorings

• Extract Method
• Extract Class
• Form Template Method
• Introduce Null Object
• Pull Up Method
• Pull Up Field
• Substitute Algorithm

Further Reading

• Don't Repeat Yourself on the C2 Wiki
• Duplicated Code on SourceMaking
• Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76

Duplicated Code

Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:

Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.

When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).

Tuning

This issue has a mass of 38.

We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.

The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.

If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.

See codeclimate-duplication's documentation for more information about tuning the mass threshold in your .codeclimate.yml.

Refactorings

• Extract Method
• Extract Class
• Form Template Method
• Introduce Null Object
• Pull Up Method
• Pull Up Field
• Substitute Algorithm

Further Reading

• Don't Repeat Yourself on the C2 Wiki
• Duplicated Code on SourceMaking
• Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76

Duplicated Code

Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:

Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.

When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).

Tuning

This issue has a mass of 38.

We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.

The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.

If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.

See codeclimate-duplication's documentation for more information about tuning the mass threshold in your .codeclimate.yml.

Refactorings

• Extract Method
• Extract Class
• Form Template Method
• Introduce Null Object
• Pull Up Method
• Pull Up Field
• Substitute Algorithm

Further Reading

• Don't Repeat Yourself on the C2 Wiki
• Duplicated Code on SourceMaking
• Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76

Duplicated Code

Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:

Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.

When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).

Tuning

This issue has a mass of 21.

We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.

The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.

If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.

See codeclimate-duplication's documentation for more information about tuning the mass threshold in your .codeclimate.yml.

Refactorings

• Extract Method
• Extract Class
• Form Template Method
• Introduce Null Object
• Pull Up Method
• Pull Up Field
• Substitute Algorithm

Further Reading

• Don't Repeat Yourself on the C2 Wiki
• Duplicated Code on SourceMaking
• Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76

Duplicated Code

Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:

Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.

When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).

Tuning

This issue has a mass of 21.

We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.

The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.

If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.

See codeclimate-duplication's documentation for more information about tuning the mass threshold in your .codeclimate.yml.

Refactorings

• Extract Method
• Extract Class
• Form Template Method
• Introduce Null Object
• Pull Up Method
• Pull Up Field
• Substitute Algorithm

Further Reading

• Don't Repeat Yourself on the C2 Wiki
• Duplicated Code on SourceMaking
• Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76

This cop enforces the use of a single string formatting utility. Valid options include Kernel#format, Kernel#sprintf and String#%.

The detection of String#% cannot be implemented in a reliable manner for all cases, so only two scenarios are considered - if the first argument is a string literal and if the second argument is an array literal.

Example: EnforcedStyle: format(default)

# bad
puts sprintf('%10s', 'hoge')
puts '%10s' % 'hoge'

# good
puts format('%10s', 'hoge')

Example: EnforcedStyle: sprintf

# bad
puts format('%10s', 'hoge')
puts '%10s' % 'hoge'

# good
puts sprintf('%10s', 'hoge')

Example: EnforcedStyle: percent

# bad
puts format('%10s', 'hoge')
puts sprintf('%10s', 'hoge')

# good
puts '%10s' % 'hoge'

This cop enforces the use of a single string formatting utility. Valid options include Kernel#format, Kernel#sprintf and String#%.

The detection of String#% cannot be implemented in a reliable manner for all cases, so only two scenarios are considered - if the first argument is a string literal and if the second argument is an array literal.

Example: EnforcedStyle: format(default)

# bad
puts sprintf('%10s', 'hoge')
puts '%10s' % 'hoge'

# good
puts format('%10s', 'hoge')

Example: EnforcedStyle: sprintf

# bad
puts format('%10s', 'hoge')
puts '%10s' % 'hoge'

# good
puts sprintf('%10s', 'hoge')

Example: EnforcedStyle: percent

# bad
puts format('%10s', 'hoge')
puts sprintf('%10s', 'hoge')

# good
puts '%10s' % 'hoge'

This cop enforces the use of a single string formatting utility. Valid options include Kernel#format, Kernel#sprintf and String#%.

The detection of String#% cannot be implemented in a reliable manner for all cases, so only two scenarios are considered - if the first argument is a string literal and if the second argument is an array literal.

Example: EnforcedStyle: format(default)

# bad
puts sprintf('%10s', 'hoge')
puts '%10s' % 'hoge'

# good
puts format('%10s', 'hoge')

Example: EnforcedStyle: sprintf

# bad
puts format('%10s', 'hoge')
puts '%10s' % 'hoge'

# good
puts sprintf('%10s', 'hoge')

Example: EnforcedStyle: percent

# bad
puts format('%10s', 'hoge')
puts sprintf('%10s', 'hoge')

# good
puts '%10s' % 'hoge'

This cop looks for use of the same name as outer local variables for block arguments or block local variables. This is a mimic of the warning "shadowing outer local variable - foo" from ruby -cw.

Example:

# bad

def some_method
  foo = 1

  2.times do |foo| # shadowing outer `foo`
    do_something(foo)
  end
end

Example:

# good

def some_method
  foo = 1

  2.times do |bar|
    do_something(bar)
  end
end

This cop checks that quotes inside the string interpolation match the configured preference.

Example: EnforcedStyle: single_quotes (default)

# bad
result = "Tests #{success ? "PASS" : "FAIL"}"

# good
result = "Tests #{success ? 'PASS' : 'FAIL'}"

Example: EnforcedStyle: double_quotes

# bad
result = "Tests #{success ? 'PASS' : 'FAIL'}"

# good
result = "Tests #{success ? "PASS" : "FAIL"}"

This cop looks for use of the same name as outer local variables for block arguments or block local variables. This is a mimic of the warning "shadowing outer local variable - foo" from ruby -cw.

Example:

# bad

def some_method
  foo = 1

  2.times do |foo| # shadowing outer `foo`
    do_something(foo)
  end
end

Example:

# good

def some_method
  foo = 1

  2.times do |bar|
    do_something(bar)
  end
end

Checks that block braces have or don't have a space before the opening brace depending on configuration.

Example:

# bad
foo.map{ |a|
  a.bar.to_s
}

# good
foo.map { |a|
  a.bar.to_s
}

This cop enforces the use of a single string formatting utility. Valid options include Kernel#format, Kernel#sprintf and String#%.

The detection of String#% cannot be implemented in a reliable manner for all cases, so only two scenarios are considered - if the first argument is a string literal and if the second argument is an array literal.

Example: EnforcedStyle: format(default)

# bad
puts sprintf('%10s', 'hoge')
puts '%10s' % 'hoge'

# good
puts format('%10s', 'hoge')

Example: EnforcedStyle: sprintf

# bad
puts format('%10s', 'hoge')
puts '%10s' % 'hoge'

# good
puts sprintf('%10s', 'hoge')

Example: EnforcedStyle: percent

# bad
puts format('%10s', 'hoge')
puts sprintf('%10s', 'hoge')

# good
puts '%10s' % 'hoge'

This cop enforces the use of a single string formatting utility. Valid options include Kernel#format, Kernel#sprintf and String#%.

The detection of String#% cannot be implemented in a reliable manner for all cases, so only two scenarios are considered - if the first argument is a string literal and if the second argument is an array literal.

Example: EnforcedStyle: format(default)

# bad
puts sprintf('%10s', 'hoge')
puts '%10s' % 'hoge'

# good
puts format('%10s', 'hoge')

Example: EnforcedStyle: sprintf

# bad
puts format('%10s', 'hoge')
puts '%10s' % 'hoge'

# good
puts sprintf('%10s', 'hoge')

Example: EnforcedStyle: percent

# bad
puts format('%10s', 'hoge')
puts sprintf('%10s', 'hoge')

# good
puts '%10s' % 'hoge'

This cop checks for uses of rescue in its modifier form.

Example:

# bad
some_method rescue handle_error

# good
begin
  some_method
rescue
  handle_error
end

This cop checks that quotes inside the string interpolation match the configured preference.

Example: EnforcedStyle: single_quotes (default)

# bad
result = "Tests #{success ? "PASS" : "FAIL"}"

# good
result = "Tests #{success ? 'PASS' : 'FAIL'}"

Example: EnforcedStyle: double_quotes

# bad
result = "Tests #{success ? 'PASS' : 'FAIL'}"

# good
result = "Tests #{success ? "PASS" : "FAIL"}"

This cop looks for use of the same name as outer local variables for block arguments or block local variables. This is a mimic of the warning "shadowing outer local variable - foo" from ruby -cw.

Example:

# bad

def some_method
  foo = 1

  2.times do |foo| # shadowing outer `foo`
    do_something(foo)
  end
end

Example:

# good

def some_method
  foo = 1

  2.times do |bar|
    do_something(bar)
  end
end

This cop checks for uses of rescue in its modifier form.

Example:

# bad
some_method rescue handle_error

# good
begin
  some_method
rescue
  handle_error
end

This cops checks if empty lines around the bodies of classes match the configuration.

Example: EnforcedStyle: empty_lines

# good

class Foo

  def bar
    # ...
  end

end

Example: EnforcedStyle: emptylinesexcept_namespace

# good

class Foo
  class Bar

    # ...

  end
end

Example: EnforcedStyle: emptylinesspecial

# good
class Foo

  def bar; end

end

Example: EnforcedStyle: noemptylines (default)

# good

class Foo
  def bar
    # ...
  end
end

This cop is designed to help upgrade to Ruby 3.0. It will add the comment # frozen_string_literal: true to the top of files to enable frozen string literals. Frozen string literals may be default in Ruby 3.0. The comment will be added below a shebang and encoding comment. The frozen string literal comment is only valid in Ruby 2.3+.

Example: EnforcedStyle: when_needed (default)

# The `when_needed` style will add the frozen string literal comment
# to files only when the `TargetRubyVersion` is set to 2.3+.
# bad
module Foo
  # ...
end

# good
# frozen_string_literal: true

module Foo
  # ...
end

Example: EnforcedStyle: always

# The `always` style will always add the frozen string literal comment
# to a file, regardless of the Ruby version or if `freeze` or `<<` are
# called on a string literal.
# bad
module Bar
  # ...
end

# good
# frozen_string_literal: true

module Bar
  # ...
end

Example: EnforcedStyle: never

# The `never` will enforce that the frozen string literal comment does
# not exist in a file.
# bad
# frozen_string_literal: true

module Baz
  # ...
end

# good
module Baz
  # ...
end

This cop checks for uses of rescue in its modifier form.

Example:

# bad
some_method rescue handle_error

# good
begin
  some_method
rescue
  handle_error
end

Checks if uses of quotes match the configured preference.

Example: EnforcedStyle: single_quotes (default)

# bad
"No special symbols"
"No string interpolation"
"Just text"

# good
'No special symbols'
'No string interpolation'
'Just text'
"Wait! What's #{this}!"

Example: EnforcedStyle: double_quotes

# bad
'Just some text'
'No special chars or interpolation'

# good
"Just some text"
"No special chars or interpolation"
"Every string in #{project} uses double_quotes"

This cop checks for missing top-level documentation of classes and modules. Classes with no body are exempt from the check and so are namespace modules - modules that have nothing in their bodies except classes, other modules, or constant definitions.

The documentation requirement is annulled if the class or module has a "#:nodoc:" comment next to it. Likewise, "#:nodoc: all" does the same for all its children.

Example:

# bad
class Person
  # ...
end

# good
# Description/Explanation of Person class
class Person
  # ...
end

This cop checks that quotes inside the string interpolation match the configured preference.

Example: EnforcedStyle: single_quotes (default)

# bad
result = "Tests #{success ? "PASS" : "FAIL"}"

# good
result = "Tests #{success ? 'PASS' : 'FAIL'}"

Example: EnforcedStyle: double_quotes

# bad
result = "Tests #{success ? 'PASS' : 'FAIL'}"

# good
result = "Tests #{success ? "PASS" : "FAIL"}"

Checks if uses of quotes match the configured preference.

Example: EnforcedStyle: single_quotes (default)

# bad
"No special symbols"
"No string interpolation"
"Just text"

# good
'No special symbols'
'No string interpolation'
'Just text'
"Wait! What's #{this}!"

Example: EnforcedStyle: double_quotes

# bad
'Just some text'
'No special chars or interpolation'

# good
"Just some text"
"No special chars or interpolation"
"Every string in #{project} uses double_quotes"