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 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

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

This cop checks for single-line method definitions that contain a body. It will accept single-line methods with no body.

Example:

# bad
def some_method; body end
def link_to(url); {:name => url}; end
def @table.columns; super; end

# good
def no_op; end
def self.resource_class=(klass); end
def @table.columns; end

This cop checks for single-line method definitions that contain a body. It will accept single-line methods with no body.

Example:

# bad
def some_method; body end
def link_to(url); {:name => url}; end
def @table.columns; super; end

# good
def no_op; end
def self.resource_class=(klass); end
def @table.columns; end

This cop checks for uses of the keyword not instead of !.

Example:

# bad - parentheses are required because of op precedence
x = (not something)

# good
x = !something

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 the keyword not instead of !.

Example:

# bad - parentheses are required because of op precedence
x = (not something)

# good
x = !something

This cop checks for uses of and and or, and suggests using && and || instead. It can be configured to check only in conditions, or in all contexts.

Example: EnforcedStyle: always (default)

# bad
foo.save and return

# bad
if foo and bar
end

# good
foo.save && return

# good
if foo && bar
end

Example: EnforcedStyle: conditionals

# bad
if foo and bar
end

# good
foo.save && return

# good
foo.save and return

# good
if foo && bar
end

This cop checks for uses of and and or, and suggests using && and || instead. It can be configured to check only in conditions, or in all contexts.

Example: EnforcedStyle: always (default)

# bad
foo.save and return

# bad
if foo and bar
end

# good
foo.save && return

# good
if foo && bar
end

Example: EnforcedStyle: conditionals

# bad
if foo and bar
end

# good
foo.save && return

# good
foo.save and return

# good
if foo && bar
end