MONGOID-5608 allow using #exists? with args on relations (#5736)

* MONGOID-5608 allow using `#exists?` with args on relations

* simplify

* test the nil/false and _id matching paths, too

lib/mongoid/association/embedded/embeds_many/proxy.rb

@@ -292,9 +292,24 @@ def destroy_all(conditions = {})
           # @example Are there persisted documents?
           #   person.posts.exists?
           #
-          # @return [ true | false ] True is persisted documents exist, false if not.
-          def exists?
-            _target.any?(&:persisted?)
+          # @param [ :none | nil | false | Hash | Object ] id_or_conditions
+          #   When :none (the default), returns true if any persisted
+          #   documents exist in the association. When nil or false, this
+          #   will always return false. When a Hash is given, this queries
+          #   the documents in the association for those that match the given
+          #   conditions, and returns true if any match which have been
+          #   persisted. Any other argument is interpreted as an id, and
+          #   queries for the existence of persisted documents in the
+          #   association with a matching _id.
+          #
+          # @return [ true | false ] True if persisted documents exist, false if not.
+          def exists?(id_or_conditions = :none)
+            case id_or_conditions
+            when :none then _target.any?(&:persisted?)
+            when nil, false then false
+            when Hash then where(id_or_conditions).any?(&:persisted?)
+            else where(_id: id_or_conditions).any?(&:persisted?)
+            end
           end
 
           # Finds a document in this association through several different

lib/mongoid/association/referenced/has_many/proxy.rb

@@ -217,9 +217,18 @@ def each(&block)
           # @example Are there persisted documents?
           #   person.posts.exists?
           #
+          # @param [ :none | nil | false | Hash | Object ] id_or_conditions
+          #   When :none (the default), returns true if any persisted
+          #   documents exist in the association. When nil or false, this
+          #   will always return false. When a Hash is given, this queries
+          #   the documents in the association for those that match the given
+          #   conditions, and returns true if any match. Any other argument is
+          #   interpreted as an id, and queries for the existence of documents
+          #   in the association with a matching _id.
+          #
           # @return [ true | false ] True is persisted documents exist, false if not.
-          def exists?
-            criteria.exists?
+          def exists?(id_or_conditions = :none)
+            criteria.exists?(id_or_conditions)
           end
 
           # Find the matching document on the association, either based on id or

spec/mongoid/association/embedded/embeds_many/proxy_spec.rb

@@ -2311,9 +2311,37 @@ class TrackingIdValidationHistory
         person.addresses.create!(street: "Bond St")
       end
 
+      let(:address) { person.addresses.first }
+
       it "returns true" do
         expect(person.addresses.exists?).to be true
       end
+
+      context 'when given specifying conditions' do
+        context 'when the record exists in the association' do
+          it 'returns true by condition' do
+            expect(person.addresses.exists?(street: 'Bond St')).to be true
+          end
+
+          it 'returns true by id' do
+            expect(person.addresses.exists?(address._id)).to be true
+          end
+
+          it 'returns false when given false' do
+            expect(person.addresses.exists?(false)).to be false
+          end
+
+          it 'returns false when given nil' do
+            expect(person.addresses.exists?(nil)).to be false
+          end
+        end
+
+        context 'when the record does not exist in the association' do
+          it 'returns false' do
+            expect(person.addresses.exists?(street: 'Garfield Ave')).to be false
+          end
+        end
+      end
     end
 
     context "when no documents exist in the database" do
@@ -2325,6 +2353,13 @@ class TrackingIdValidationHistory
       it "returns false" do
         expect(person.addresses.exists?).to be false
       end
+
+      context 'when given specifying conditions' do
+        it 'returns false' do
+          expect(person.addresses.exists?(street: 'Hyde Park Dr')).to be false
+          expect(person.addresses.exists?(street: 'Garfield Ave')).to be false
+        end
+      end
     end
   end
 

spec/mongoid/association/referenced/has_many/proxy_spec.rb

@@ -1924,6 +1924,42 @@ def with_transaction_via(model, &block)
           expect_query(1) { expect(person.posts.exists?).to be true }
         end
       end
+
+      context 'when invoked with specifying conditions' do
+        let(:other_person) { Person.create! }
+        let(:post) { person.posts.first }
+
+        before do
+          person.posts.create title: 'bumfuzzle'
+          other_person.posts.create title: 'bumbershoot'
+        end
+
+        context 'when the conditions match an associated record' do
+          it 'detects its existence by condition' do
+            expect(person.posts.exists?(title: 'bumfuzzle')).to be true
+            expect(other_person.posts.exists?(title: 'bumbershoot')).to be true
+          end
+
+          it 'detects its existence by id' do
+            expect(person.posts.exists?(post._id)).to be true
+          end
+
+          it 'returns false when given false' do
+            expect(person.posts.exists?(false)).to be false
+          end
+
+          it 'returns false when given nil' do
+            expect(person.posts.exists?(nil)).to be false
+          end
+        end
+
+        context 'when the conditions match an unassociated record' do
+          it 'does not detect its existence' do
+            expect(person.posts.exists?(title: 'bumbershoot')).to be false
+            expect(other_person.posts.exists?(title: 'bumfuzzle')).to be false
+          end
+        end
+      end
     end
 
     context 'when documents exist in application but not in database' do
@@ -1972,6 +2008,12 @@ def with_transaction_via(model, &block)
           expect_query(1) { expect(person.posts.exists?).to be false }
         end
       end
+
+      context 'when invoked with specifying conditions' do
+        it 'returns false' do
+          expect(person.posts.exists?(title: 'hullaballoo')).to be false
+        end
+      end
     end
   end