Customize RuboCop Layout/ClassStructure cop I’m really proud to announce my new contribuition to RuboCop.
Some days ago I contributed improving the development page, creating a getting started guide and also creating a new tutorial to explain how Node Pattern works.
Now, the Layout/ClassStructure cop was merged and it allows us to specify the order of the elements in the class definition.
Initially it follows the community style guide and follows the order:
- Include, Extend or Prepend First
- Constants
- Initializer
- Public methods
- Protected methods
- Private methods
It’s also very easy to extend the cop and include new rules in the middle.
The basic configuration says:
Layout/ClassStructure:
Enabled: false
Categories:
module_inclusion:
- include
- prepend
- extend
ExpectedOrder:
- module_inclusion
- constants
- public_class_methods
- initializer
- instance_methods
- protected_methods
- private_methods
Lets imagine you got sad about people saying validates after define methods
and also mess with other macros from ActiveRecord.
Lets say we want to have strict rules in Rails models and use the following order:
- Include, Extend or Prepend First
- Constants
- Attributes (attribute, attr_accessor, attr_reader, attr_writer)
- Associations (belongs_to, has_many, has_and_belongs_to_many …)
- Validations (validate, validates_presence_of, validates_uniqueness_of …)
- Hooks (before_save, after_save, after_initialize …)
- Initializer
- Public methods
- Protected methods
- Private methods
Now we need to setup Categories and include them in the ExpectedOrder.
Layout/ClassStructure:
Enabled: true
Categories:
module_inclusion:
- include
- prepend
- extend
attributes:
- attribute
- attr_reader
- attr_writer
- attr_accessor
associations:
- has_one
- has_many
- belongs_to
- has_and_belongs_to_many
validations:
- validate
- validates_presence_of
- validates_uniqueness_of
hooks:
- after_save
- after_create
- after_initialize
ExpectedOrder:
- module_inclusion
- constants
- attributes
- associations
- validations
- hooks
- public_class_methods
- initializer
- public_methods
- protected_methods
- private_methods
Now it’s ready to be tested.
Lets use a example with a few mistakes:
class User
validate :name, :email, presence: true
attr_reader :temporary_orders
validates_uniqueness_of :email
def email_domain
email.split('@').last
end
has_many :orders
after_create :send_welcome_email
belongs_to :location
end
It supports autocorrect, and running it you can check that RuboCop has a kind of loop to keep autocorrecting until it’s perfect.
user.rb:3:3: C: [Corrected] Layout/ClassStructure: attributes is supposed to appear before associations.
attr_reader :temporary_orders
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
user.rb:3:3: C: [Corrected] Layout/ClassStructure: attributes is supposed to appear before validations.
attr_reader :temporary_orders
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
user.rb:5:3: C: [Corrected] Layout/ClassStructure: associations is supposed to appear before hooks.
belongs_to :location
^^^^^^^^^^^^^^^^^^^^
user.rb:5:3: C: [Corrected] Layout/ClassStructure: associations is supposed to appear before validations.
has_many :orders
^^^^^^^^^^^^^^^^
user.rb:6:3: C: [Corrected] Layout/ClassStructure: associations is supposed to appear before validations.
belongs_to :location
^^^^^^^^^^^^^^^^^^^^
user.rb:6:3: C: [Corrected] Layout/ClassStructure: validations is supposed to appear before hooks.
validate :name, :email, presence: true
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
user.rb:8:3: C: [Corrected] Layout/ClassStructure: validations is supposed to appear before hooks.
validates_uniqueness_of :email
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
This feature is very cool because allow the cops algorithm simply execute one swap between the nodes that are not in the proper place. Then you can see it in action recursively until the file is totally organized.
After autocorrect the file looks like this:
class User
attr_reader :temporary_orders
has_many :orders
belongs_to :location
validates_uniqueness_of :email
validate :name, :email, presence: true
after_create :send_welcome_email
def email_domain
email.split('@').last
end
end
So, that is what this cop does. I hope this cop to be useful for the community and make our code classes more organized. If you’re interested in the full history you can check my Pull Request here.