Add support for acts_as_tenant :through (#275)

* Add support for acts_as_tenant :through. This allows you to use acts_as_tenant for has-and-belongs-to-many relationships.

* Update readme to include  option.

README.md

@@ -210,6 +210,28 @@ You can also explicitly specifiy a primary_key for AaT to use should the key dif
 acts_as_tenant(:account, :primary_key => 'primaryID') # by default AaT expects id
 ```
 
+
+### Has and belongs to many ###
+
+You can scope a model that is part of a HABTM relationship by using the `through` option.
+
+```ruby
+class Organisation < ActiveRecord::Base
+  has_many :organisations_users
+  has_many :users, through: :organisations_users
+end
+
+class User < ActiveRecord::Base
+  has_many :organisations_users
+  acts_as_tenant :organisation, through: :organisations_users
+end
+
+class OrganisationsUser < ActiveRecord::Base
+  belongs_to :user
+  acts_as_tenant :organisation
+end
+```
+
 Configuration options
 ---------------------
 An initializer can be created to control (currently one) option in ActsAsTenant. Defaults

lib/acts_as_tenant/model_extensions.rb

@@ -24,9 +24,15 @@ def acts_as_tenant(tenant = :account, **options)
             keys = [ActsAsTenant.current_tenant.send(pkey)].compact
             keys.push(nil) if options[:has_global_records]
 
-            query_criteria = {fkey.to_sym => keys}
-            query_criteria[polymorphic_type.to_sym] = ActsAsTenant.current_tenant.class.to_s if options[:polymorphic]
-            where(query_criteria)
+            if options[:through]
+              query_criteria = {options[:through] => {fkey.to_sym => keys}}
+              query_criteria[polymorphic_type.to_sym] = ActsAsTenant.current_tenant.class.to_s if options[:polymorphic]
+              joins(options[:through]).where(query_criteria)
+            else
+              query_criteria = {fkey.to_sym => keys}
+              query_criteria[polymorphic_type.to_sym] = ActsAsTenant.current_tenant.class.to_s if options[:polymorphic]
+              where(query_criteria)
+            end
           else
             all
           end

spec/dummy/app/models/account.rb

@@ -1,4 +1,6 @@
 class Account < ActiveRecord::Base
   has_many :projects
   has_many :global_projects
+  has_many :users_accounts
+  has_many :users, through: :users_accounts
 end

spec/dummy/app/models/user.rb

@@ -0,0 +1,6 @@
+class User < ActiveRecord::Base
+  has_many :users_accounts
+  has_many :accounts, through: :users_accounts
+
+  acts_as_tenant :account, through: :users_accounts
+end

spec/dummy/app/models/users_account.rb

@@ -0,0 +1,4 @@
+class UsersAccount < ActiveRecord::Base
+  acts_as_tenant :account
+  belongs_to :user
+end

spec/dummy/db/schema.rb

@@ -81,4 +81,14 @@
     t.column :polymorphic_tenant_commentable_type, :string
     t.column :account_id, :integer
   end
+
+  create_table :users, force: true do |t|
+    t.column :name, :string
+  end
+
+  create_table :users_accounts, force: true do |t|
+    t.column :user_id, :integer
+    t.column :account_id, :integer
+    t.index [:user_id, :account_id], name: :index_users_accounts_on_user_id_and_account_id, unique: true
+  end
 end

spec/fixtures/accounts.yml

@@ -8,3 +8,11 @@ with_domain:
   name: domain
   subdomain: domain
   domain: domain.com
+
+abc:
+  name: abc
+  users: john, bob # habtm relation
+
+def:
+  name: def
+  users: john, alice # habtm relation

spec/fixtures/users.yml

@@ -0,0 +1,8 @@
+john:
+  name: john
+
+bob:
+  name: bob
+
+alice:
+  name: alice

spec/models/model_extensions_spec.rb

@@ -104,6 +104,25 @@
     end
   end
 
+  describe "acts_as_tenant :through" do
+    let(:account) { accounts(:abc) }
+
+    it "should scope User.all to the current tenant if set" do
+      ActsAsTenant.current_tenant = account
+      expect(User.count).to eq(account.users.count)
+      expect(User.all).to eq(account.users)
+    end
+
+    it "should return all users when no current tenant is set" do
+      expect(User.count).to eq(3)
+    end
+
+    it "should allow unscoping" do
+      ActsAsTenant.current_tenant = account
+      expect(User.unscoped.count).to be > account.users.count
+    end
+  end
+
   describe "A tenant model with global records" do
     before do
       ActsAsTenant.current_tenant = account