TracksApp/tracks

Flog calculates the ABC score for methods. The ABC score is based on assignments, branches (method calls), and conditions.

You can read more about ABC metrics or the flog tool

A method with Too Many Statements is any method that has a large number of lines.

Too Many Statements warns about any method that has more than 5 statements. Reek's smell detector for Too Many Statements counts +1 for every simple statement in a method and +1 for every statement within a control structure (if, else, case, when, for, while, until, begin, rescue) but it doesn't count the control structure itself.

So the following method would score +6 in Reek's statement-counting algorithm:

def parse(arg, argv, &error)
  if !(val = arg) and (argv.empty? or /\A-/ =~ (val = argv[0]))
    return nil, block, nil                                         # +1
  end
  opt = (val = parse_arg(val, &error))[1]                          # +2
  val = conv_arg(*val)                                             # +3
  if opt and !arg
    argv.shift                                                     # +4
  else
    val[0] = nil                                                   # +5
  end
  val                                                              # +6
end

(You might argue that the two assigments within the first @if@ should count as statements, and that perhaps the nested assignment should count as +2.)

A method with Too Many Statements is any method that has a large number of lines.

Too Many Statements warns about any method that has more than 5 statements. Reek's smell detector for Too Many Statements counts +1 for every simple statement in a method and +1 for every statement within a control structure (if, else, case, when, for, while, until, begin, rescue) but it doesn't count the control structure itself.

So the following method would score +6 in Reek's statement-counting algorithm:

def parse(arg, argv, &error)
  if !(val = arg) and (argv.empty? or /\A-/ =~ (val = argv[0]))
    return nil, block, nil                                         # +1
  end
  opt = (val = parse_arg(val, &error))[1]                          # +2
  val = conv_arg(*val)                                             # +3
  if opt and !arg
    argv.shift                                                     # +4
  else
    val[0] = nil                                                   # +5
  end
  val                                                              # +6
end

(You might argue that the two assigments within the first @if@ should count as statements, and that perhaps the nested assignment should count as +2.)

Flog calculates the ABC score for methods. The ABC score is based on assignments, branches (method calls), and conditions.

You can read more about ABC metrics or the flog tool

Duplication occurs when two fragments of code look nearly identical, or when two fragments of code have nearly identical effects at some conceptual level.

Reek implements a check for Duplicate Method Call.

Example

Here's a very much simplified and contrived example. The following method will report a warning:

def double_thing()
  @other.thing + @other.thing
end

One quick approach to silence Reek would be to refactor the code thus:

def double_thing()
  thing = @other.thing
  thing + thing
end

A slightly different approach would be to replace all calls of double_thing by calls to @other.double_thing:

class Other
  def double_thing()
    thing + thing
  end
end

The approach you take will depend on balancing other factors in your code.

Classes and modules are the units of reuse and release. It is therefore considered good practice to annotate every class and module with a brief comment outlining its responsibilities.

Example

Given

class Dummy
  # Do things...
end

Reek would emit the following warning:

test.rb -- 1 warning:
  [1]:Dummy has no descriptive comment (IrresponsibleModule)

Fixing this is simple - just an explaining comment:

# The Dummy class is responsible for ...
class Dummy
  # Do things...
end

Duplication occurs when two fragments of code look nearly identical, or when two fragments of code have nearly identical effects at some conceptual level.

Reek implements a check for Duplicate Method Call.

Example

Here's a very much simplified and contrived example. The following method will report a warning:

def double_thing()
  @other.thing + @other.thing
end

One quick approach to silence Reek would be to refactor the code thus:

def double_thing()
  thing = @other.thing
  thing + thing
end

A slightly different approach would be to replace all calls of double_thing by calls to @other.double_thing:

class Other
  def double_thing()
    thing + thing
  end
end

The approach you take will depend on balancing other factors in your code.

Duplication occurs when two fragments of code look nearly identical, or when two fragments of code have nearly identical effects at some conceptual level.

Reek implements a check for Duplicate Method Call.

Example

Here's a very much simplified and contrived example. The following method will report a warning:

def double_thing()
  @other.thing + @other.thing
end

One quick approach to silence Reek would be to refactor the code thus:

def double_thing()
  thing = @other.thing
  thing + thing
end

A slightly different approach would be to replace all calls of double_thing by calls to @other.double_thing:

class Other
  def double_thing()
    thing + thing
  end
end

The approach you take will depend on balancing other factors in your code.

Classes should not assume that instance variables are set or present outside of the current class definition.

Good:

class Foo
  def initialize
    @bar = :foo
  end

  def foo?
    @bar == :foo
  end
end

Good as well:

class Foo
  def foo?
    bar == :foo
  end

  def bar
    @bar ||= :foo
  end
end

Bad:

class Foo
  def go_foo!
    @bar = :foo
  end

  def foo?
    @bar == :foo
  end
end

Example

Running Reek on:

class Dummy
  def test
    @ivar
  end
end

would report:

[1]:InstanceVariableAssumption: Dummy assumes too much for instance variable @ivar

Note that this example would trigger this smell warning as well:

class Parent
  def initialize(omg)
    @omg = omg
  end
end

class Child < Parent
  def foo
    @omg
  end
end

The way to address the smell warning is that you should create an attr_reader to use @omg in the subclass and not access @omg directly like this:

class Parent
  attr_reader :omg

  def initialize(omg)
    @omg = omg
  end
end

class Child < Parent
  def foo
    omg
  end
end

Directly accessing instance variables is considered a smell because it breaks encapsulation and makes it harder to reason about code.

If you don't want to expose those methods as public API just make them private like this:

class Parent
  def initialize(omg)
    @omg = omg
  end

  private
  attr_reader :omg
end

class Child < Parent
  def foo
    omg
  end
end

Current Support in Reek

An instance variable must:

• be set in the constructor
• or be accessed through a method with lazy initialization / memoization.

If not, Instance Variable Assumption will be reported.

A NilCheck is a type check. Failures of NilCheck violate the "tell, don't ask" principle.

Additionally, type checks often mask bigger problems in your source code like not using OOP and / or polymorphism when you should.

Example

Given

class Klass
  def nil_checker(argument)
    if argument.nil?
      puts "argument isn't nil!"
    end
  end
end

Reek would emit the following warning:

test.rb -- 1 warning:
  [3]:Klass#nil_checker performs a nil-check. (NilCheck)

This cop checks for the use of methods which skip validations which are listed in http://guides.rubyonrails.org/active_record_validations.html#skipping-validations

Example:

# bad
Article.first.decrement!(:view_count)
DiscussionBoard.decrement_counter(:post_count, 5)
Article.first.increment!(:view_count)
DiscussionBoard.increment_counter(:post_count, 5)
person.toggle :active
product.touch
Billing.update_all("category = 'authorized', author = 'David'")
user.update_attribute(website: 'example.com')
user.update_columns(last_request_at: Time.current)
Post.update_counters 5, comment_count: -1, action_count: 1

# good
user.update_attributes(website: 'example.com')
FileUtils.touch('file')

This cop checks for comparison of something with nil using ==.

Example:

# bad
if x == nil
end

# good
if x.nil?
end

This cop checks for redundant parentheses.

Example:

# bad
(x) if ((y.z).nil?)

# good
x if y.z.nil?

This cop checks for the presence of parentheses around ternary conditions. It is configurable to enforce inclusion or omission of parentheses using EnforcedStyle. Omission is only enforced when removing the parentheses won't cause a different behavior.

Example: EnforcedStyle: requirenoparentheses (default)

# bad
foo = (bar?) ? a : b
foo = (bar.baz?) ? a : b
foo = (bar && baz) ? a : b

# good
foo = bar? ? a : b
foo = bar.baz? ? a : b
foo = bar && baz ? a : b

Example: EnforcedStyle: require_parentheses

# bad
foo = bar? ? a : b
foo = bar.baz? ? a : b
foo = bar && baz ? a : b

# good
foo = (bar?) ? a : b
foo = (bar.baz?) ? a : b
foo = (bar && baz) ? a : b

Example: EnforcedStyle: requireparentheseswhen_complex

# bad
foo = (bar?) ? a : b
foo = (bar.baz?) ? a : b
foo = bar && baz ? a : b

# good
foo = bar? ? a : b
foo = bar.baz? ? a : b
foo = (bar && baz) ? a : b

Checks for if and unless statements that would fit on one line if written as a modifier if/unless. The maximum line length is configured in the Metrics/LineLength cop.

Example:

# bad
if condition
  do_stuff(bar)
end

unless qux.empty?
  Foo.do_something
end

# good
do_stuff(bar) if condition
Foo.do_something unless qux.empty?

This cop can check for array literals made up of symbols that are not using the %i() syntax.

Alternatively, it checks for symbol arrays using the %i() syntax on projects which do not want to use that syntax.

Configuration option: MinSize If set, arrays with fewer elements than this value will not trigger the cop. For example, a MinSize of3` will not enforce a style on an array of 2 or fewer elements.

Example: EnforcedStyle: percent (default)

# good
%i[foo bar baz]

# bad
[:foo, :bar, :baz]

Example: EnforcedStyle: brackets

# good
[:foo, :bar, :baz]

# bad
%i[foo bar baz]

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