DEV: Have contract take a block in services

Currently in services, the `contract` step is only used to define where
the contract will be called in the execution flow. Then, a `Contract`
class has to be defined with validations in it.

This patch allows the `contract` step to take a block containing
validations, attributes, etc. directly. No need to then open a
`Contract` class later in the service.

It also has a nice side effect, as it’s now easy to define multiples
contracts inside the same service. Before, we had the `class_name:`
option, but it wasn’t really useful as you had to redefine a complete
new contract class.
Now, when using a name for the contract other than `default`, a new
contract will be created automatically using the provided name.

Example:
```ruby
contract(:user) do
  attribute :user_id, :integer

  validates :user_id, presence: true
end
```
This will create a `UserContract` class and use it, also putting the
resulting contract in `context[:user_contract]`.

app/services/flags/create_flag.rb

@@ -3,28 +3,26 @@
 class Flags::CreateFlag
   include Service::Base
 
-  contract
-  policy :invalid_access
-  policy :unique_name
-  model :flag, :instantiate_flag
-
-  transaction do
-    step :create
-    step :log
-  end
-
-  class Contract
+  contract do
     attribute :name, :string
     attribute :description, :string
     attribute :require_message, :boolean
     attribute :enabled, :boolean
     attribute :applies_to
+
     validates :name, presence: true
     validates :description, presence: true
     validates :name, length: { maximum: Flag::MAX_NAME_LENGTH }
     validates :description, length: { maximum: Flag::MAX_DESCRIPTION_LENGTH }
     validates :applies_to, inclusion: { in: -> { Flag.valid_applies_to_types } }, allow_nil: false
   end
+  policy :invalid_access
+  policy :unique_name
+  model :flag, :instantiate_flag
+  transaction do
+    step :create
+    step :log
+  end
 
   private
 

app/services/flags/reorder_flag.rb

@@ -5,23 +5,21 @@ VALID_DIRECTIONS = %w[up down]
 class Flags::ReorderFlag
   include Service::Base
 
-  contract
+  contract do
+    attribute :flag_id, :integer
+    attribute :direction, :string
+
+    validates :flag_id, presence: true
+    validates :direction, inclusion: { in: VALID_DIRECTIONS }
+  end
   model :flag
   policy :invalid_access
   policy :invalid_move
-
   transaction do
     step :move
     step :log
   end
 
-  class Contract
-    attribute :flag_id, :integer
-    attribute :direction, :string
-    validates :flag_id, presence: true
-    validates :direction, inclusion: { in: VALID_DIRECTIONS }
-  end
-
   private
 
   def fetch_flag(flag_id:)

app/services/flags/toggle_flag.rb

@@ -3,20 +3,18 @@
 class Flags::ToggleFlag
   include Service::Base
 
-  contract
+  contract do
+    attribute :flag_id, :integer
+
+    validates :flag_id, presence: true
+  end
   model :flag
   policy :invalid_access
-
   transaction do
     step :toggle
     step :log
   end
 
-  class Contract
-    attribute :flag_id, :integer
-    validates :flag_id, presence: true
-  end
-
   private
 
   def fetch_flag(flag_id:)

app/services/flags/update_flag.rb

@@ -3,30 +3,28 @@
 class Flags::UpdateFlag
   include Service::Base
 
-  contract
-  model :flag
-  policy :not_system
-  policy :not_used
-  policy :invalid_access
-  policy :unique_name
-
-  transaction do
-    step :update
-    step :log
-  end
-
-  class Contract
+  contract do
     attribute :name, :string
     attribute :description, :string
     attribute :require_message, :boolean
     attribute :enabled, :boolean
     attribute :applies_to
+
     validates :name, presence: true
     validates :description, presence: true
     validates :name, length: { maximum: Flag::MAX_NAME_LENGTH }
     validates :description, length: { maximum: Flag::MAX_DESCRIPTION_LENGTH }
     validates :applies_to, inclusion: { in: -> { Flag.valid_applies_to_types } }, allow_nil: false
   end
+  model :flag
+  policy :not_system
+  policy :not_used
+  policy :invalid_access
+  policy :unique_name
+  transaction do
+    step :update
+    step :log
+  end
 
   private
 

app/services/update_site_setting.rb

@@ -4,20 +4,18 @@ class UpdateSiteSetting
   include Service::Base
 
   policy :current_user_is_admin
-  contract
-  step :convert_name_to_sym
-  policy :setting_is_visible
-  policy :setting_is_configurable
-  step :cleanup_value
-  step :save
-
-  class Contract
+  contract do
     attribute :setting_name
     attribute :new_value
     attribute :allow_changing_hidden, :boolean, default: false
 
     validates :setting_name, presence: true
   end
+  step :convert_name_to_sym
+  policy :setting_is_visible
+  policy :setting_is_configurable
+  step :cleanup_value
+  step :save
 
   private
 

app/services/user/silence.rb

@@ -3,16 +3,7 @@
 class User::Silence
   include Service::Base
 
-  contract
-  model :user
-  policy :not_silenced_already, class_name: User::Policy::NotAlreadySilenced
-  model :users
-  policy :can_silence_all_users
-  step :silence
-  model :post, optional: true
-  step :perform_post_action
-
-  class Contract
+  contract do
     attribute :user_id, :integer
     attribute :reason, :string
     attribute :message, :string
@@ -28,6 +19,13 @@ class User::Silence
     validates :other_user_ids, length: { maximum: User::MAX_SIMILAR_USERS }
     validates :post_action, inclusion: { in: %w[delete delete_replies edit] }, allow_blank: true
   end
+  model :user
+  policy :not_silenced_already, class_name: User::Policy::NotAlreadySilenced
+  model :users
+  policy :can_silence_all_users
+  step :silence
+  model :post, optional: true
+  step :perform_post_action
 
   private
 

app/services/user/suspend.rb

@@ -3,16 +3,7 @@
 class User::Suspend
   include Service::Base
 
-  contract
-  model :user
-  policy :not_suspended_already, class_name: User::Policy::NotAlreadySuspended
-  model :users
-  policy :can_suspend_all_users
-  step :suspend
-  model :post, optional: true
-  step :perform_post_action
-
-  class Contract
+  contract do
     attribute :user_id, :integer
     attribute :reason, :string
     attribute :message, :string
@@ -28,6 +19,13 @@ class User::Suspend
     validates :other_user_ids, length: { maximum: User::MAX_SIMILAR_USERS }
     validates :post_action, inclusion: { in: %w[delete delete_replies edit] }, allow_blank: true
   end
+  model :user
+  policy :not_suspended_already, class_name: User::Policy::NotAlreadySuspended
+  model :users
+  policy :can_suspend_all_users
+  step :suspend
+  model :post, optional: true
+  step :perform_post_action
 
   private