MONGOID-5149 Skip inverse detection when inverse_of: nil is set (#5027)

* Skipping inverse relation detection when inverse_of: nil is set

* Extracting a specific spec for the matter at hand

lib/mongoid/association/relatable.rb

@@ -122,6 +122,8 @@ def bindable?(doc); false; end
       # @since 7.0
       def inverses(other = nil)
         return [ inverse_of ] if inverse_of
+        return [] if @options.key?(:inverse_of) && !inverse_of
+
         if polymorphic?
           polymorphic_inverses(other)
         else

spec/mongoid/association/referenced/belongs_to_query_spec.rb

@@ -35,4 +35,24 @@
       expect(school.team).to eq('Bulldogs')
     end
   end
+
+  context 'when projecting with #only while having similar inverse_of candidates' do
+    before do
+      alice = HmmOwner.create!(name: 'Alice')
+      bob = HmmOwner.create!(name: 'Bob')
+
+      HmmPet.create!(name: 'Rex', current_owner: bob, previous_owner: alice)
+    end
+
+    let(:pet) { HmmPet.where(name: 'Rex').only(:name, :previous_owner_id, 'previous_owner.name').first }
+
+    it 'populates specified fields' do
+      expect(pet.name).to eq('Rex')
+      expect(pet.previous_owner.name).to eq('Alice')
+    end
+
+    it 'does not try to load the inverse for an association that explicitly prevents it' do
+      expect { pet.previous_owner.name }.not_to raise_error
+    end
+  end
 end

spec/mongoid/association/referenced/has_many_models.rb

@@ -24,6 +24,23 @@ class HmmAddress
   belongs_to :company, class_name: 'HmmCompany'
 end
 
+class HmmOwner
+  include Mongoid::Document
+
+  has_many :pets, class_name: 'HmmPet', inverse_of: :current_owner
+
+  field :name, type: String
+end
+
+class HmmPet
+  include Mongoid::Document
+
+  belongs_to :current_owner, class_name: 'HmmOwner', inverse_of: :pets, optional: true
+  belongs_to :previous_owner, class_name: 'HmmOwner', inverse_of: nil, optional: true
+
+  field :name, type: String
+end
+
 class HmmSchool
   include Mongoid::Document