This warning comes up if a model does not limit what attributes can be set through mass assignment.

In particular, this check looks for attr_accessible inside model definitions. If it is not found, this warning will be issued.

Brakeman also warns on use of attr_protected - especially since it was found to be vulnerable to bypass. Warnings for mass assignment on models using attr_protected will be reported, but at a lower confidence level.

Note that disabling mass assignment globally will suppress these warnings.

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

You can set literals you want to fold with CountAsOne. Available are: 'array', 'hash', and 'heredoc'. Each literal will be counted as one line regardless of its actual size.

Example: CountAsOne: ['array', 'heredoc']

class Foo
  ARRAY = [         # +1
    1,
    2
  ]

  HASH = {          # +3
    key: 'value'
  }

  MSG = <<~HEREDOC  # +1
    Heredoc
    content.
  HEREDOC
end                 # 5 points

NOTE: This cop also applies for Struct definitions.

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

You can set literals you want to fold with CountAsOne. Available are: 'array', 'hash', and 'heredoc'. Each literal will be counted as one line regardless of its actual size.

NOTE: The ExcludedMethods and IgnoredMethods configuration is deprecated and only kept for backwards compatibility. Please use AllowedMethods and AllowedPatterns instead. By default, there are no methods to allowed.

Example: CountAsOne: ['array', 'heredoc']

def m
  array = [       # +1
    1,
    2
  ]

  hash = {        # +3
    key: 'value'
  }

  <<~HEREDOC      # +1
    Heredoc
    content.
  HEREDOC
end               # 5 points

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

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.

Interpreting ABC size:

• <= 17 satisfactory
• 18..30 unsatisfactory
• > 30 dangerous

You can have repeated "attributes" calls count as a single "branch". For this purpose, attributes are any method with no argument; no attempt is meant to distinguish actual attr_reader from other methods.

Example: CountRepeatedAttributes: false (default is true)

# `model` and `current_user`, referenced 3 times each,
 # are each counted as only 1 branch each if
 # `CountRepeatedAttributes` is set to 'false'

 def search
   @posts = model.active.visible_by(current_user)
             .search(params[:q])
   @posts = model.some_process(@posts, current_user)
   @posts = model.another_process(@posts, current_user)

   render 'pages/search/page'
 end

This cop also takes into account AllowedMethods (defaults to []) And AllowedPatterns (defaults to [])

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.

Interpreting ABC size:

• <= 17 satisfactory
• 18..30 unsatisfactory
• > 30 dangerous

You can have repeated "attributes" calls count as a single "branch". For this purpose, attributes are any method with no argument; no attempt is meant to distinguish actual attr_reader from other methods.

Example: CountRepeatedAttributes: false (default is true)

# `model` and `current_user`, referenced 3 times each,
 # are each counted as only 1 branch each if
 # `CountRepeatedAttributes` is set to 'false'

 def search
   @posts = model.active.visible_by(current_user)
             .search(params[:q])
   @posts = model.some_process(@posts, current_user)
   @posts = model.another_process(@posts, current_user)

   render 'pages/search/page'
 end

This cop also takes into account AllowedMethods (defaults to []) And AllowedPatterns (defaults to [])

In Ruby 2.4, String#match?, Regexp#match? and Symbol#match? have been added. The methods are faster than match. Because the methods avoid creating a MatchData object or saving backref. So, when MatchData is not used, use match? instead of match.

Example:

# bad
def foo
  if x =~ /re/
    do_something
  end
end

# bad
def foo
  if x.match(/re/)
    do_something
  end
end

# bad
def foo
  if /re/ === x
    do_something
  end
end

# good
def foo
  if x.match?(/re/)
    do_something
  end
end

# good
def foo
  if x =~ /re/
    do_something(Regexp.last_match)
  end
end

# good
def foo
  if x.match(/re/)
    do_something($~)
  end
end

# good
def foo
  if /re/ === x
    do_something($~)
  end
end

This cop looks for has_many or has_one associations that don't specify a :dependent option. It doesn't register an offense if :through option was specified.

Example:

# bad
class User < ActiveRecord::Base
  has_many :comments
  has_one :avatar
end

# good
class User < ActiveRecord::Base
  has_many :comments, dependent: :restrict_with_exception
  has_one :avatar, dependent: :destroy
  has_many :patients, through: :appointments
end

This cop looks for has_many or has_one associations that don't specify a :dependent option. It doesn't register an offense if :through option was specified.

Example:

# bad
class User < ActiveRecord::Base
  has_many :comments
  has_one :avatar
end

# good
class User < ActiveRecord::Base
  has_many :comments, dependent: :restrict_with_exception
  has_one :avatar, dependent: :destroy
  has_many :patients, through: :appointments
end

This cop checks that models subclass ApplicationRecord with Rails 5.0.

Example:

# good class Rails5Model < ApplicationRecord # ... end

# bad class Rails4Model < ActiveRecord::Base # ... end

This cop looks for has(one|many) and belongsto associations where Active Record can't automatically determine the inverse association because of a scope or the options used. Using the blog with order scope example below, traversing the a Blog's association in both directions with blog.posts.first.blog would cause the blog to be loaded from the database twice.

:inverse_of must be manually specified for Active Record to use the associated object in memory, or set to false to opt-out. Note that setting nil does not stop Active Record from trying to determine the inverse automatically, and is not considered a valid value for this.

Example:

# good
class Blog < ApplicationRecord
  has_many :posts
end

class Post < ApplicationRecord
  belongs_to :blog
end

Example:

# bad
class Blog < ApplicationRecord
  has_many :posts, -> { order(published_at: :desc) }
end

class Post < ApplicationRecord
  belongs_to :blog
end

# good
class Blog < ApplicationRecord
  has_many(:posts,
           -> { order(published_at: :desc) },
           inverse_of: :blog)
end

class Post < ApplicationRecord
  belongs_to :blog
end

# good
class Blog < ApplicationRecord
  with_options inverse_of: :blog do
    has_many :posts, -> { order(published_at: :desc) }
  end
end

class Post < ApplicationRecord
  belongs_to :blog
end

# good
# When you don't want to use the inverse association.
class Blog < ApplicationRecord
  has_many(:posts,
           -> { order(published_at: :desc) },
           inverse_of: false)
end

Example:

# bad
class Picture < ApplicationRecord
  belongs_to :imageable, polymorphic: true
end

class Employee < ApplicationRecord
  has_many :pictures, as: :imageable
end

class Product < ApplicationRecord
  has_many :pictures, as: :imageable
end

# good
class Picture < ApplicationRecord
  belongs_to :imageable, polymorphic: true
end

class Employee < ApplicationRecord
  has_many :pictures, as: :imageable, inverse_of: :imageable
end

class Product < ApplicationRecord
  has_many :pictures, as: :imageable, inverse_of: :imageable
end

Example:

# bad
# However, RuboCop can not detect this pattern...
class Physician < ApplicationRecord
  has_many :appointments
  has_many :patients, through: :appointments
end

class Appointment < ApplicationRecord
  belongs_to :physician
  belongs_to :patient
end

class Patient < ApplicationRecord
  has_many :appointments
  has_many :physicians, through: :appointments
end

# good
class Physician < ApplicationRecord
  has_many :appointments
  has_many :patients, through: :appointments
end

class Appointment < ApplicationRecord
  belongs_to :physician, inverse_of: :appointments
  belongs_to :patient, inverse_of: :appointments
end

class Patient < ApplicationRecord
  has_many :appointments
  has_many :physicians, through: :appointments
end

@see https://guides.rubyonrails.org/association_basics.html#bi-directional-associations @see https://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html#module-ActiveRecord::Associations::ClassMethods-label-Setting+Inverses

This cop looks for has(one|many) and belongsto associations where Active Record can't automatically determine the inverse association because of a scope or the options used. Using the blog with order scope example below, traversing the a Blog's association in both directions with blog.posts.first.blog would cause the blog to be loaded from the database twice.

:inverse_of must be manually specified for Active Record to use the associated object in memory, or set to false to opt-out. Note that setting nil does not stop Active Record from trying to determine the inverse automatically, and is not considered a valid value for this.

Example:

# good
class Blog < ApplicationRecord
  has_many :posts
end

class Post < ApplicationRecord
  belongs_to :blog
end

Example:

# bad
class Blog < ApplicationRecord
  has_many :posts, -> { order(published_at: :desc) }
end

class Post < ApplicationRecord
  belongs_to :blog
end

# good
class Blog < ApplicationRecord
  has_many(:posts,
           -> { order(published_at: :desc) },
           inverse_of: :blog)
end

class Post < ApplicationRecord
  belongs_to :blog
end

# good
class Blog < ApplicationRecord
  with_options inverse_of: :blog do
    has_many :posts, -> { order(published_at: :desc) }
  end
end

class Post < ApplicationRecord
  belongs_to :blog
end

# good
# When you don't want to use the inverse association.
class Blog < ApplicationRecord
  has_many(:posts,
           -> { order(published_at: :desc) },
           inverse_of: false)
end

Example:

# bad
class Picture < ApplicationRecord
  belongs_to :imageable, polymorphic: true
end

class Employee < ApplicationRecord
  has_many :pictures, as: :imageable
end

class Product < ApplicationRecord
  has_many :pictures, as: :imageable
end

# good
class Picture < ApplicationRecord
  belongs_to :imageable, polymorphic: true
end

class Employee < ApplicationRecord
  has_many :pictures, as: :imageable, inverse_of: :imageable
end

class Product < ApplicationRecord
  has_many :pictures, as: :imageable, inverse_of: :imageable
end

Example:

# bad
# However, RuboCop can not detect this pattern...
class Physician < ApplicationRecord
  has_many :appointments
  has_many :patients, through: :appointments
end

class Appointment < ApplicationRecord
  belongs_to :physician
  belongs_to :patient
end

class Patient < ApplicationRecord
  has_many :appointments
  has_many :physicians, through: :appointments
end

# good
class Physician < ApplicationRecord
  has_many :appointments
  has_many :patients, through: :appointments
end

class Appointment < ApplicationRecord
  belongs_to :physician, inverse_of: :appointments
  belongs_to :patient, inverse_of: :appointments
end

class Patient < ApplicationRecord
  has_many :appointments
  has_many :physicians, through: :appointments
end

@see https://guides.rubyonrails.org/association_basics.html#bi-directional-associations @see https://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html#module-ActiveRecord::Associations::ClassMethods-label-Setting+Inverses

This cop looks for has_many or has_one associations that don't specify a :dependent option. It doesn't register an offense if :through option was specified.

Example:

# bad
class User < ActiveRecord::Base
  has_many :comments
  has_one :avatar
end

# good
class User < ActiveRecord::Base
  has_many :comments, dependent: :restrict_with_exception
  has_one :avatar, dependent: :destroy
  has_many :patients, through: :appointments
end

Checks the length of lines in the source code. The maximum length is configurable. The tab size is configured in the IndentationWidth of the Layout/IndentationStyle cop. It also ignores a shebang line by default.

This cop has some autocorrection capabilities. It can programmatically shorten certain long lines by inserting line breaks into expressions that can be safely split across lines. These include arrays, hashes, and method calls with argument lists.

If autocorrection is enabled, the following Layout cops are recommended to further format the broken lines. (Many of these are enabled by default.)

• ArgumentAlignment
• ArrayAlignment
• BlockAlignment
• BlockDelimiters
• BlockEndNewline
• ClosingParenthesisIndentation
• FirstArgumentIndentation
• FirstArrayElementIndentation
• FirstHashElementIndentation
• FirstParameterIndentation
• HashAlignment
• IndentationWidth
• MultilineArrayLineBreaks
• MultilineBlockLayout
• MultilineHashBraceLayout
• MultilineHashKeyLineBreaks
• MultilineMethodArgumentLineBreaks
• MultilineMethodParameterLineBreaks
• ParameterAlignment

Together, these cops will pretty print hashes, arrays, method calls, etc. For example, let's say the max columns is 25:

Example:

# bad
{foo: "0000000000", bar: "0000000000", baz: "0000000000"}

# good
{foo: "0000000000",
bar: "0000000000", baz: "0000000000"}

# good (with recommended cops enabled)
{
  foo: "0000000000",
  bar: "0000000000",
  baz: "0000000000",
}

Looks for expressions containing multiple binary operators where precedence is ambiguous due to lack of parentheses. For example, in 1 + 2 * 3, the multiplication will happen before the addition, but lexically it appears that the addition will happen first.

The cop does not consider unary operators (ie. !a or -b) or comparison operators (ie. a =~ b) because those are not ambiguous.

NOTE: Ranges are handled by Lint/AmbiguousRange.

Example:

# bad
a + b * c
a || b && c
a ** b + c

# good (different precedence)
a + (b * c)
a || (b && c)
(a ** b) + c

# good (same precedence)
a + b + c
a * b / c % d

Check for uses of braces or do/end around single line or multi-line blocks.

Methods that can be either procedural or functional and cannot be categorised from their usage alone is ignored. lambda, proc, and it are their defaults. Additional methods can be added to the AllowedMethods.

Example: EnforcedStyle: linecountbased (default)

# bad - single line block
items.each do |item| item / 5 end

# good - single line block
items.each { |item| item / 5 }

# bad - multi-line block
things.map { |thing|
  something = thing.some_method
  process(something)
}

# good - multi-line block
things.map do |thing|
  something = thing.some_method
  process(something)
end

Example: EnforcedStyle: semantic

# Prefer `do...end` over `{...}` for procedural blocks.

# return value is used/assigned
# bad
foo = map do |x|
  x
end
puts (map do |x|
  x
end)

# return value is not used out of scope
# good
map do |x|
  x
end

# Prefer `{...}` over `do...end` for functional blocks.

# return value is not used out of scope
# bad
each { |x|
  x
}

# return value is used/assigned
# good
foo = map { |x|
  x
}
map { |x|
  x
}.inspect

# The AllowBracesOnProceduralOneLiners option is allowed unless the
# EnforcedStyle is set to `semantic`. If so:

# If the AllowBracesOnProceduralOneLiners option is unspecified, or
# set to `false` or any other falsey value, then semantic purity is
# maintained, so one-line procedural blocks must use do-end, not
# braces.

# bad
collection.each { |element| puts element }

# good
collection.each do |element| puts element end

# If the AllowBracesOnProceduralOneLiners option is set to `true`, or
# any other truthy value, then one-line procedural blocks may use
# either style. (There is no setting for requiring braces on them.)

# good
collection.each { |element| puts element }

# also good
collection.each do |element| puts element end

Example: EnforcedStyle: bracesforchaining

# bad
words.each do |word|
  word.flip.flop
end.join("-")

# good
words.each { |word|
  word.flip.flop
}.join("-")

Example: EnforcedStyle: always_braces

# bad
words.each do |word|
  word.flip.flop
end

# good
words.each { |word|
  word.flip.flop
}

Example: BracesRequiredMethods: ['sig']

# Methods listed in the BracesRequiredMethods list, such as 'sig'
# in this example, will require `{...}` braces. This option takes
# precedence over all other configurations except AllowedMethods.

# bad
sig do
  params(
    foo: string,
  ).void
end
def bar(foo)
  puts foo
end

# good
sig {
  params(
    foo: string,
  ).void
}
def bar(foo)
  puts foo
end

Example: AllowedMethods: ['lambda', 'proc', 'it' ] (default)

# good
foo = lambda do |x|
  puts "Hello, #{x}"
end

foo = lambda do |x|
  x * 100
end

Example: AllowedPatterns: [] (default)

# bad
things.map { |thing|
  something = thing.some_method
  process(something)
}

Example: AllowedPatterns: ['map']

# good
things.map { |thing|
  something = thing.some_method
  process(something)
}

Here we check if the arguments on a multi-line method definition are aligned.

Example: EnforcedStyle: withfirstargument (default)

# good

foo :bar,
    :baz,
    key: value

foo(
  :bar,
  :baz,
  key: value
)

# bad

foo :bar,
  :baz,
  key: value

foo(
  :bar,
    :baz,
    key: value
)

Example: EnforcedStyle: withfixedindentation

# good

foo :bar,
  :baz,
  key: value

# bad

foo :bar,
    :baz,
    key: value

Looks for expressions containing multiple binary operators where precedence is ambiguous due to lack of parentheses. For example, in 1 + 2 * 3, the multiplication will happen before the addition, but lexically it appears that the addition will happen first.

The cop does not consider unary operators (ie. !a or -b) or comparison operators (ie. a =~ b) because those are not ambiguous.

NOTE: Ranges are handled by Lint/AmbiguousRange.

Example:

# bad
a + b * c
a || b && c
a ** b + c

# good (different precedence)
a + (b * c)
a || (b && c)
(a ** b) + c

# good (same precedence)
a + b + c
a * b / c % d

Checks method parameter names for how descriptive they are. It is highly configurable.

The MinNameLength config option takes an integer. It represents the minimum amount of characters the name must be. Its default is 3. The AllowNamesEndingInNumbers config option takes a boolean. When set to false, this cop will register offenses for names ending with numbers. Its default is false. The AllowedNames config option takes an array of permitted names that will never register an offense. The ForbiddenNames config option takes an array of restricted names that will always register an offense.

Example:

# bad
def bar(varOne, varTwo)
  varOne + varTwo
end

# With `AllowNamesEndingInNumbers` set to false
def foo(num1, num2)
  num1 * num2
end

# With `MinNameLength` set to number greater than 1
def baz(a, b, c)
  do_stuff(a, b, c)
end

# good
def bar(thud, fred)
  thud + fred
end

def foo(speed, distance)
  speed * distance
end

def baz(age_a, height_b, gender_c)
  do_stuff(age_a, height_b, gender_c)
end

Checks hash literal syntax.

It can enforce either the use of the class hash rocket syntax or the use of the newer Ruby 1.9 syntax (when applicable).

A separate offense is registered for each problematic pair.

The supported styles are:

• ruby19 - forces use of the 1.9 syntax (e.g. {a: 1}) when hashes have all symbols for keys
• hash_rockets - forces use of hash rockets for all hashes
• nomixedkeys - simply checks for hashes with mixed syntaxes
• ruby19nomixed_keys - forces use of ruby 1.9 syntax and forbids mixed syntax hashes

This cop has EnforcedShorthandSyntax option. It can enforce either the use of the explicit hash value syntax or the use of Ruby 3.1's hash value shorthand syntax.

The supported styles are:

• always - forces use of the 3.1 syntax (e.g. {foo:})
• never - forces use of explicit hash literal value
• either - accepts both shorthand and explicit use of hash literal value
• consistent - like "either", but will avoid mixing styles in a single hash

Example: EnforcedStyle: ruby19 (default)

# bad
{:a => 2}
{b: 1, :c => 2}

# good
{a: 2, b: 1}
{:c => 2, 'd' => 2} # acceptable since 'd' isn't a symbol
{d: 1, 'e' => 2} # technically not forbidden

Example: EnforcedStyle: hash_rockets

# bad
{a: 1, b: 2}
{c: 1, 'd' => 5}

# good
{:a => 1, :b => 2}

Example: EnforcedStyle: nomixedkeys

# bad
{:a => 1, b: 2}
{c: 1, 'd' => 2}

# good
{:a => 1, :b => 2}
{c: 1, d: 2}

Example: EnforcedStyle: ruby19nomixed_keys

# bad
{:a => 1, :b => 2}
{c: 2, 'd' => 3} # should just use hash rockets

# good
{a: 1, b: 2}
{:c => 3, 'd' => 4}

Example: EnforcedShorthandSyntax: always (default)

# bad
{foo: foo, bar: bar}

# good
{foo:, bar:}

Example: EnforcedShorthandSyntax: never

# bad
{foo:, bar:}

# good
{foo: foo, bar: bar}

Example: EnforcedShorthandSyntax: either

# good
{foo: foo, bar: bar}

# good
{foo:, bar:}

Example: EnforcedShorthandSyntax: consistent

# bad
{foo: , bar: bar}

# good
{foo:, bar:}

# bad
{foo: , bar: baz}

# good
{foo: foo, bar: baz}

Looks for expressions containing multiple binary operators where precedence is ambiguous due to lack of parentheses. For example, in 1 + 2 * 3, the multiplication will happen before the addition, but lexically it appears that the addition will happen first.

The cop does not consider unary operators (ie. !a or -b) or comparison operators (ie. a =~ b) because those are not ambiguous.

NOTE: Ranges are handled by Lint/AmbiguousRange.

Example:

# bad
a + b * c
a || b && c
a ** b + c

# good (different precedence)
a + (b * c)
a || (b && c)
(a ** b) + c

# good (same precedence)
a + b + c
a * b / c % d

Looks for expressions containing multiple binary operators where precedence is ambiguous due to lack of parentheses. For example, in 1 + 2 * 3, the multiplication will happen before the addition, but lexically it appears that the addition will happen first.

The cop does not consider unary operators (ie. !a or -b) or comparison operators (ie. a =~ b) because those are not ambiguous.

NOTE: Ranges are handled by Lint/AmbiguousRange.

Example:

# bad
a + b * c
a || b && c
a ** b + c

# good (different precedence)
a + (b * c)
a || (b && c)
(a ** b) + c

# good (same precedence)
a + b + c
a * b / c % d

Checks hash literal syntax.

It can enforce either the use of the class hash rocket syntax or the use of the newer Ruby 1.9 syntax (when applicable).

A separate offense is registered for each problematic pair.

The supported styles are:

• ruby19 - forces use of the 1.9 syntax (e.g. {a: 1}) when hashes have all symbols for keys
• hash_rockets - forces use of hash rockets for all hashes
• nomixedkeys - simply checks for hashes with mixed syntaxes
• ruby19nomixed_keys - forces use of ruby 1.9 syntax and forbids mixed syntax hashes

This cop has EnforcedShorthandSyntax option. It can enforce either the use of the explicit hash value syntax or the use of Ruby 3.1's hash value shorthand syntax.

The supported styles are:

• always - forces use of the 3.1 syntax (e.g. {foo:})
• never - forces use of explicit hash literal value
• either - accepts both shorthand and explicit use of hash literal value
• consistent - like "either", but will avoid mixing styles in a single hash

Example: EnforcedStyle: ruby19 (default)

# bad
{:a => 2}
{b: 1, :c => 2}

# good
{a: 2, b: 1}
{:c => 2, 'd' => 2} # acceptable since 'd' isn't a symbol
{d: 1, 'e' => 2} # technically not forbidden

Example: EnforcedStyle: hash_rockets

# bad
{a: 1, b: 2}
{c: 1, 'd' => 5}

# good
{:a => 1, :b => 2}

Example: EnforcedStyle: nomixedkeys

# bad
{:a => 1, b: 2}
{c: 1, 'd' => 2}

# good
{:a => 1, :b => 2}
{c: 1, d: 2}

Example: EnforcedStyle: ruby19nomixed_keys

# bad
{:a => 1, :b => 2}
{c: 2, 'd' => 3} # should just use hash rockets

# good
{a: 1, b: 2}
{:c => 3, 'd' => 4}

Example: EnforcedShorthandSyntax: always (default)

# bad
{foo: foo, bar: bar}

# good
{foo:, bar:}

Example: EnforcedShorthandSyntax: never

# bad
{foo:, bar:}

# good
{foo: foo, bar: bar}

Example: EnforcedShorthandSyntax: either

# good
{foo: foo, bar: bar}

# good
{foo:, bar:}

Example: EnforcedShorthandSyntax: consistent

# bad
{foo: , bar: bar}

# good
{foo:, bar:}

# bad
{foo: , bar: baz}

# good
{foo: foo, bar: baz}

Checks for chaining of a block after another block that spans multiple lines.

Example:

# bad
Thread.list.select do |t|
  t.alive?
end.map do |t|
  t.object_id
end

# good
alive_threads = Thread.list.select do |t|
  t.alive?
end
alive_threads.map do |t|
  t.object_id
end

Checks for a redundant argument passed to certain methods.

NOTE: This cop is limited to methods with single parameter.

Method names and their redundant arguments can be configured like this:

Methods:
  join: ''
  split: ' '
  chomp: "\n"
  chomp!: "\n"
  foo: 2

Safety:

This cop is unsafe because of the following limitations:

1. This cop matches by method names only and hence cannot tell apart methods with same name in different classes.
2. This cop may be unsafe if certain special global variables (e.g. $;, $/) are set. That depends on the nature of the target methods, of course. For example, the default argument to join is $OUTPUT_FIELD_SEPARATOR (or $,) rather than '', and if that global is changed, '' is no longer a redundant argument.

Example:

# bad
array.join('')
[1, 2, 3].join("")
string.split(" ")
"first\nsecond".split(" ")
string.chomp("\n")
string.chomp!("\n")
A.foo(2)

# good
array.join
[1, 2, 3].join
string.split
"first second".split
string.chomp
string.chomp!
A.foo

Looks for expressions containing multiple binary operators where precedence is ambiguous due to lack of parentheses. For example, in 1 + 2 * 3, the multiplication will happen before the addition, but lexically it appears that the addition will happen first.

The cop does not consider unary operators (ie. !a or -b) or comparison operators (ie. a =~ b) because those are not ambiguous.

NOTE: Ranges are handled by Lint/AmbiguousRange.

Example:

# bad
a + b * c
a || b && c
a ** b + c

# good (different precedence)
a + (b * c)
a || (b && c)
(a ** b) + c

# good (same precedence)
a + b + c
a * b / c % d

Enforces the consistent usage of %-literal delimiters.

Specify the 'default' key to set all preferred delimiters at once. You can continue to specify individual preferred delimiters to override the default.

Example:

# Style/PercentLiteralDelimiters:
#   PreferredDelimiters:
#     default: '[]'
#     '%i':    '()'

# good
%w[alpha beta] + %i(gamma delta)

# bad
%W(alpha #{beta})

# bad
%I(alpha beta)

Checks hash literal syntax.

It can enforce either the use of the class hash rocket syntax or the use of the newer Ruby 1.9 syntax (when applicable).

A separate offense is registered for each problematic pair.

The supported styles are:

• ruby19 - forces use of the 1.9 syntax (e.g. {a: 1}) when hashes have all symbols for keys
• hash_rockets - forces use of hash rockets for all hashes
• nomixedkeys - simply checks for hashes with mixed syntaxes
• ruby19nomixed_keys - forces use of ruby 1.9 syntax and forbids mixed syntax hashes

This cop has EnforcedShorthandSyntax option. It can enforce either the use of the explicit hash value syntax or the use of Ruby 3.1's hash value shorthand syntax.

The supported styles are:

• always - forces use of the 3.1 syntax (e.g. {foo:})
• never - forces use of explicit hash literal value
• either - accepts both shorthand and explicit use of hash literal value
• consistent - like "either", but will avoid mixing styles in a single hash

Example: EnforcedStyle: ruby19 (default)

# bad
{:a => 2}
{b: 1, :c => 2}

# good
{a: 2, b: 1}
{:c => 2, 'd' => 2} # acceptable since 'd' isn't a symbol
{d: 1, 'e' => 2} # technically not forbidden

Example: EnforcedStyle: hash_rockets

# bad
{a: 1, b: 2}
{c: 1, 'd' => 5}

# good
{:a => 1, :b => 2}

Example: EnforcedStyle: nomixedkeys

# bad
{:a => 1, b: 2}
{c: 1, 'd' => 2}

# good
{:a => 1, :b => 2}
{c: 1, d: 2}

Example: EnforcedStyle: ruby19nomixed_keys

# bad
{:a => 1, :b => 2}
{c: 2, 'd' => 3} # should just use hash rockets

# good
{a: 1, b: 2}
{:c => 3, 'd' => 4}

Example: EnforcedShorthandSyntax: always (default)

# bad
{foo: foo, bar: bar}

# good
{foo:, bar:}

Example: EnforcedShorthandSyntax: never

# bad
{foo:, bar:}

# good
{foo: foo, bar: bar}

Example: EnforcedShorthandSyntax: either

# good
{foo: foo, bar: bar}

# good
{foo:, bar:}

Example: EnforcedShorthandSyntax: consistent

# bad
{foo: , bar: bar}

# good
{foo:, bar:}

# bad
{foo: , bar: baz}

# good
{foo: foo, bar: baz}

Checks method parameter names for how descriptive they are. It is highly configurable.

The MinNameLength config option takes an integer. It represents the minimum amount of characters the name must be. Its default is 3. The AllowNamesEndingInNumbers config option takes a boolean. When set to false, this cop will register offenses for names ending with numbers. Its default is false. The AllowedNames config option takes an array of permitted names that will never register an offense. The ForbiddenNames config option takes an array of restricted names that will always register an offense.

Example:

# bad
def bar(varOne, varTwo)
  varOne + varTwo
end

# With `AllowNamesEndingInNumbers` set to false
def foo(num1, num2)
  num1 * num2
end

# With `MinNameLength` set to number greater than 1
def baz(a, b, c)
  do_stuff(a, b, c)
end

# good
def bar(thud, fred)
  thud + fred
end

def foo(speed, distance)
  speed * distance
end

def baz(age_a, height_b, gender_c)
  do_stuff(age_a, height_b, gender_c)
end

Enforces the consistent usage of %-literal delimiters.

Specify the 'default' key to set all preferred delimiters at once. You can continue to specify individual preferred delimiters to override the default.

Example:

# Style/PercentLiteralDelimiters:
#   PreferredDelimiters:
#     default: '[]'
#     '%i':    '()'

# good
%w[alpha beta] + %i(gamma delta)

# bad
%W(alpha #{beta})

# bad
%I(alpha beta)