StrictAssociations

What it does

Summary

Enforces explicit definitions of both sides of ActiveRecord associations (e.g. belongs_to, has_many)

StrictAssociations enforces 5 rules:

1. :missing_inverse - Every belongs_to must have a corresponding has_many or has_one on the target model pointing back
2. :missing_dependent - Every direct has_many or has_one must declare a :dependent option (:destroy, :nullify, etc)
3. :unregistered_polymorphic - Every polymorphic belongs_to must declare :valid_types
4. :missing_polymorphic_inverse - Each registered polymorphic type must have a has_many or has_one pointing back
5. :habtm_banned - No has_and_belongs_to_many allowed

How to use

Normal case: StrictAssociation enforces doing it right

class Foo < ApplicationRecord
end

class Bar < ApplicationRecord
  belongs_to :foo
end

# => StrictAssociation::ViolationError
#
# We failed to define the has_many association

class Foo < ApplicationRecord
  has_many :bars
end

class Bar < ApplicationRecord
  belongs_to :foo
end

# => StrictAssociation::ViolationError
#
# We failed to define the :dependent option for the has_many association

class Foo < ApplicationRecord
  has_many :bars, dependent: :destroy
end

class Bar < ApplicationRecord
  belongs_to :foo
end

# => Good

Ignore in cases where StrictAssociations don't make sense

# "I know this model doesn't have a has_many pointing back; that's intentional"
belongs_to :foo, strict: false

# "I'm handling dependents manually" (e.g. such as in a callback)
has_many :bars, strict: false

# "I'm purposely not defining the association"
skip_strict_association :bars

Sample error message

StrictAssociations found 1 violation(s): (StrictAssociations::ViolationError)

Foo.bars [missing_dependent]: Foo#bars is missing a :dependent option.
Add dependent: :destroy, :delete_all, :nullify, or :restrict_with_exception. Or mark
with strict: false. Or call skip_strict_association :bars on Foo.

Polymorphic associations

You must specify valid_types for polymorphic models. These are then also checked along with other strict associations.

Example

class Role < ActiveRecord::Base
  belongs_to :resource, polymorphic: true
end

class Document < ActiveRecord::Base
  has_many :roles, dependent: :destroy
end

# => StrictAssociation::ViolationError
# We failed to define :valid_types for the polymorphic belongs_to

class Role < ActiveRecord::Base
  belongs_to :resource, polymorphic: true, valid_types: %i[Document Organization]
end

class Document < ActiveRecord::Base
end

# => StrictAssociation::ViolationError
# We failed to define the has_many

class Role < ActiveRecord::Base
  belongs_to :resource, polymorphic: true, valid_types: %i[Document Organization]
end

class Document < ActiveRecord::Base
  has_many :roles, dependent: :destroy
end

# => Good