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 25.

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

Use a guard clause instead of wrapping the code inside a conditional expression

Example:

# bad
def test
  if something
    work
  end
end

# good
def test
  return unless something
  work
end

# also good
def test
  work if something
end

# bad
if something
  raise 'exception'
else
  ok
end

# good
raise 'exception' if something
ok

This cop checks for the use of output safety calls like htmlsafe, raw, and safeconcat. These methods do not escape content. They simply return a SafeBuffer containing the content as is. Instead, use safe_join to join content and escape it and concat to concatenate content and escape it, ensuring its safety.

Example:

user_content = "hi"

# bad
"
#{user_content}
".html_safe
# => ActiveSupport::SafeBuffer "
hi
"

# good
content_tag(:p, user_content)
# => ActiveSupport::SafeBuffer "
<b>hi</b>
"

# bad
out = ""
out << "
#{user_content}
"
out << "
#{user_content}
"
out.html_safe
# => ActiveSupport::SafeBuffer "
hi
hi
"

# good
out = []
out << content_tag(:li, user_content)
out << content_tag(:li, user_content)
safe_join(out)
# => ActiveSupport::SafeBuffer
#    "
<b>hi</b>
<b>hi</b>
"

# bad
out = "
trusted content
".html_safe
out.safe_concat(user_content)
# => ActiveSupport::SafeBuffer "
trusted_content
hi"

# good
out = "
trusted content
".html_safe
out.concat(user_content)
# => ActiveSupport::SafeBuffer
#    "
trusted_content
<b>hi</b>"

# safe, though maybe not good style
out = "trusted content"
result = out.concat(user_content)
# => String "trusted contenthi"
# because when rendered in ERB the String will be escaped:
# <%= result %>
# => trusted content<b>hi</b>

# bad
(user_content + " " + content_tag(:span, user_content)).html_safe
# => ActiveSupport::SafeBuffer "hi <span><b>hi</b></span>"

# good
safe_join([user_content, " ", content_tag(:span, user_content)])
# => ActiveSupport::SafeBuffer
#    "<b>hi</b> <span>&lt;b&gt;hi&lt;/b&gt;</span>"

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 makes sure that all variables use the configured style, snake_case or camelCase, for their names.

Example: EnforcedStyle: snake_case (default)

# bad
fooBar = 1

# good
foo_bar = 1

Example: EnforcedStyle: camelCase

# bad
foo_bar = 1

# good
fooBar = 1

This cop checks for the use of Time methods without zone.

Built on top of Ruby on Rails style guide (https://github.com/bbatsov/rails-style-guide#time) and the article http://danilenko.org/2012/7/6/rails_timezones/ .

Two styles are supported for this cop. When EnforcedStyle is 'strict' then only use of Time.zone is allowed.

When EnforcedStyle is 'flexible' then it's also allowed to use Time.intimezone.

Example:

# always offense
Time.now
Time.parse('2015-03-02 19:05:37')

# no offense
Time.zone.now
Time.zone.parse('2015-03-02 19:05:37')

# no offense only if style is 'flexible'
Time.current
DateTime.strptime(str, "%Y-%m-%d %H:%M %Z").in_time_zone
Time.at(timestamp).in_time_zone

This cop checks for assignments in the conditions of if/while/until.

Example:

# bad

if some_var = true
  do_something
end

Example:

# good

if some_var == true
  do_something
end

This cop looks for has(one|many) and belongsto associations where ActiveRecord can't automatically determine the inverse association because of a scope or the options used. This can result in unnecessary queries in some circumstances. :inverse_of must be manually specified for associations to work in both ways, or set to false to opt-out.

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

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

This cop checks for the use of output safety calls like htmlsafe, raw, and safeconcat. These methods do not escape content. They simply return a SafeBuffer containing the content as is. Instead, use safe_join to join content and escape it and concat to concatenate content and escape it, ensuring its safety.

Example:

user_content = "hi"

# bad
"
#{user_content}
".html_safe
# => ActiveSupport::SafeBuffer "
hi
"

# good
content_tag(:p, user_content)
# => ActiveSupport::SafeBuffer "
<b>hi</b>
"

# bad
out = ""
out << "
#{user_content}
"
out << "
#{user_content}
"
out.html_safe
# => ActiveSupport::SafeBuffer "
hi
hi
"

# good
out = []
out << content_tag(:li, user_content)
out << content_tag(:li, user_content)
safe_join(out)
# => ActiveSupport::SafeBuffer
#    "
<b>hi</b>
<b>hi</b>
"

# bad
out = "
trusted content
".html_safe
out.safe_concat(user_content)
# => ActiveSupport::SafeBuffer "
trusted_content
hi"

# good
out = "
trusted content
".html_safe
out.concat(user_content)
# => ActiveSupport::SafeBuffer
#    "
trusted_content
<b>hi</b>"

# safe, though maybe not good style
out = "trusted content"
result = out.concat(user_content)
# => String "trusted contenthi"
# because when rendered in ERB the String will be escaped:
# <%= result %>
# => trusted content<b>hi</b>

# bad
(user_content + " " + content_tag(:span, user_content)).html_safe
# => ActiveSupport::SafeBuffer "hi <span><b>hi</b></span>"

# good
safe_join([user_content, " ", content_tag(:span, user_content)])
# => ActiveSupport::SafeBuffer
#    "<b>hi</b> <span>&lt;b&gt;hi&lt;/b&gt;</span>"

This cop checks for every useless assignment to local variable in every scope. The basic idea for this cop was from the warning of ruby -cw:

assigned but unused variable - foo

Currently this cop has advanced logic that detects unreferenced reassignments and properly handles varied cases such as branch, loop, rescue, ensure, etc.

Example:

# bad

def some_method
  some_var = 1
  do_something
end

Example:

# good

def some_method
  some_var = 1
  do_something(some_var)
end

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 the use of output safety calls like htmlsafe, raw, and safeconcat. These methods do not escape content. They simply return a SafeBuffer containing the content as is. Instead, use safe_join to join content and escape it and concat to concatenate content and escape it, ensuring its safety.

Example:

user_content = "hi"

# bad
"
#{user_content}
".html_safe
# => ActiveSupport::SafeBuffer "
hi
"

# good
content_tag(:p, user_content)
# => ActiveSupport::SafeBuffer "
<b>hi</b>
"

# bad
out = ""
out << "
#{user_content}
"
out << "
#{user_content}
"
out.html_safe
# => ActiveSupport::SafeBuffer "
hi
hi
"

# good
out = []
out << content_tag(:li, user_content)
out << content_tag(:li, user_content)
safe_join(out)
# => ActiveSupport::SafeBuffer
#    "
<b>hi</b>
<b>hi</b>
"

# bad
out = "
trusted content
".html_safe
out.safe_concat(user_content)
# => ActiveSupport::SafeBuffer "
trusted_content
hi"

# good
out = "
trusted content
".html_safe
out.concat(user_content)
# => ActiveSupport::SafeBuffer
#    "
trusted_content
<b>hi</b>"

# safe, though maybe not good style
out = "trusted content"
result = out.concat(user_content)
# => String "trusted contenthi"
# because when rendered in ERB the String will be escaped:
# <%= result %>
# => trusted content<b>hi</b>

# bad
(user_content + " " + content_tag(:span, user_content)).html_safe
# => ActiveSupport::SafeBuffer "hi <span><b>hi</b></span>"

# good
safe_join([user_content, " ", content_tag(:span, user_content)])
# => ActiveSupport::SafeBuffer
#    "<b>hi</b> <span>&lt;b&gt;hi&lt;/b&gt;</span>"

This cop checks for every useless assignment to local variable in every scope. The basic idea for this cop was from the warning of ruby -cw:

assigned but unused variable - foo

Currently this cop has advanced logic that detects unreferenced reassignments and properly handles varied cases such as branch, loop, rescue, ensure, etc.

Example:

# bad

def some_method
  some_var = 1
  do_something
end

Example:

# good

def some_method
  some_var = 1
  do_something(some_var)
end

This cop looks for has(one|many) and belongsto associations where ActiveRecord can't automatically determine the inverse association because of a scope or the options used. This can result in unnecessary queries in some circumstances. :inverse_of must be manually specified for associations to work in both ways, or set to false to opt-out.

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

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

This cop makes sure that all variables use the configured style, snake_case or camelCase, for their names.

Example: EnforcedStyle: snake_case (default)

# bad
fooBar = 1

# good
foo_bar = 1

Example: EnforcedStyle: camelCase

# bad
foo_bar = 1

# good
fooBar = 1

Use a guard clause instead of wrapping the code inside a conditional expression

Example:

# bad
def test
  if something
    work
  end
end

# good
def test
  return unless something
  work
end

# also good
def test
  work if something
end

# bad
if something
  raise 'exception'
else
  ok
end

# good
raise 'exception' if something
ok