From 0c48936a50f4f9a5f155ec4294a26a1768cd00a1 Mon Sep 17 00:00:00 2001
From: johnnyshields <27655+johnnyshields@users.noreply.github.com>
Date: Tue, 5 Sep 2023 00:55:51 +0900
Subject: [PATCH 1/6] __mongoize_fk step 1: move code to right class

---
 lib/mongoid/extensions/array.rb         |  17 ---
 lib/mongoid/extensions/object.rb        |  15 ---
 lib/mongoid/fields/foreign_key.rb       |  25 +++-
 spec/mongoid/extensions/array_spec.rb   | 150 ------------------------
 spec/mongoid/extensions/object_spec.rb  |  91 --------------
 spec/mongoid/fields/foreign_key_spec.rb | 142 ++++++++++++++++++++++
 6 files changed, 166 insertions(+), 274 deletions(-)

diff --git a/lib/mongoid/extensions/array.rb b/lib/mongoid/extensions/array.rb
index 812ac620da..bba6d613a7 100644
--- a/lib/mongoid/extensions/array.rb
+++ b/lib/mongoid/extensions/array.rb
@@ -122,23 +122,6 @@ def resizable?
 
       module ClassMethods
 
-        # Convert the provided object to a proper array of foreign keys.
-        #
-        # @example Mongoize the object.
-        #   Array.__mongoize_fk__(constraint, object)
-        #
-        # @param [ Mongoid::Association::Relatable ] association The association metadata.
-        # @param [ Object ] object The object to convert.
-        #
-        # @return [ Array ] The array of ids.
-        def __mongoize_fk__(association, object)
-          if object.resizable?
-            object.blank? ? object : association.convert_to_foreign_key(object)
-          else
-            object.blank? ? [] : association.convert_to_foreign_key(Array(object))
-          end
-        end
-
         # Turn the object from the ruby type we deal with to a Mongo friendly
         # type.
         #
diff --git a/lib/mongoid/extensions/object.rb b/lib/mongoid/extensions/object.rb
index ec0cd89f91..4d55ee10d2 100644
--- a/lib/mongoid/extensions/object.rb
+++ b/lib/mongoid/extensions/object.rb
@@ -203,21 +203,6 @@ def you_must(name, *args)
 
       module ClassMethods
 
-        # Convert the provided object to a foreign key, given the metadata key
-        # contstraint.
-        #
-        # @example Convert the object to a fk.
-        #   Object.__mongoize_fk__(association, object)
-        #
-        # @param [ Mongoid::Association::Relatable ] association The association metadata.
-        # @param [ Object ] object The object to convert.
-        #
-        # @return [ Object ] The converted object.
-        def __mongoize_fk__(association, object)
-          return nil if !object || object == ""
-          association.convert_to_foreign_key(object)
-        end
-
         # Convert the object from its mongo friendly ruby type to this type.
         #
         # @example Demongoize the object.
diff --git a/lib/mongoid/fields/foreign_key.rb b/lib/mongoid/fields/foreign_key.rb
index 19cb802ab9..5e0b7f1df3 100644
--- a/lib/mongoid/fields/foreign_key.rb
+++ b/lib/mongoid/fields/foreign_key.rb
@@ -95,7 +95,7 @@ def lazy?
       # @return [ Object ] The mongoized object.
       def mongoize(object)
         if type.resizable? || object_id_field?
-          type.__mongoize_fk__(association, object)
+          mongoize_foreign_key(type, association, object)
         else
           related_id_field.mongoize(object)
         end
@@ -124,6 +124,29 @@ def resizable?
 
       private
 
+      # Convert the provided object to a foreign key, given the type
+      # and metadata key constraint.
+      #
+      # @example Convert the object to a fk.
+      #   mongoize_foreign_key(Array, association, object)
+      #
+      # @param [ Class ] type The association metadata.
+      # @param [ Mongoid::Association::Relatable ] association The association metadata.
+      # @param [ Object ] object The object to convert.
+      #
+      # @return [ Object ] The converted object.
+      def mongoize_foreign_key(type, association, object)
+        if type == Array
+          if object.resizable?
+            object.blank? ? object : association.convert_to_foreign_key(object)
+          else
+            object.blank? ? [] : association.convert_to_foreign_key(Array(object))
+          end
+        elsif !(object.nil? || object == '')
+          association.convert_to_foreign_key(object)
+        end
+      end
+
       # Evaluate the default proc. In some cases we need to instance exec,
       # in others we don't.
       #
diff --git a/spec/mongoid/extensions/array_spec.rb b/spec/mongoid/extensions/array_spec.rb
index 18ab1ee2f2..4019f6f1c2 100644
--- a/spec/mongoid/extensions/array_spec.rb
+++ b/spec/mongoid/extensions/array_spec.rb
@@ -203,156 +203,6 @@
     end
   end
 
-  describe ".__mongoize_fk__" do
-
-    context "when the related model uses object ids" do
-
-      let(:association) do
-        Person.relations["preferences"]
-      end
-
-      context "when provided an object id" do
-
-        let(:object_id) do
-          BSON::ObjectId.new
-        end
-
-        let(:fk) do
-          Array.__mongoize_fk__(association, object_id)
-        end
-
-        it "returns the object id as an array" do
-          expect(fk).to eq([ object_id ])
-        end
-      end
-
-      context "when provided a object ids" do
-
-        let(:object_id) do
-          BSON::ObjectId.new
-        end
-
-        let(:fk) do
-          Array.__mongoize_fk__(association, [ object_id ])
-        end
-
-        it "returns the object ids" do
-          expect(fk).to eq([ object_id ])
-        end
-      end
-
-      context "when provided a string" do
-
-        context "when the string is a legal object id" do
-
-          let(:object_id) do
-            BSON::ObjectId.new
-          end
-
-          let(:fk) do
-            Array.__mongoize_fk__(association, object_id.to_s)
-          end
-
-          it "returns the object id in an array" do
-            expect(fk).to eq([ object_id ])
-          end
-        end
-
-        context "when the string is not a legal object id" do
-
-          let(:string) do
-            "blah"
-          end
-
-          let(:fk) do
-            Array.__mongoize_fk__(association, string)
-          end
-
-          it "returns the string in an array" do
-            expect(fk).to eq([ string ])
-          end
-        end
-
-        context "when the string is blank" do
-
-          let(:fk) do
-            Array.__mongoize_fk__(association, "")
-          end
-
-          it "returns an empty array" do
-            expect(fk).to be_empty
-          end
-        end
-      end
-
-      context "when provided nil" do
-
-        let(:fk) do
-          Array.__mongoize_fk__(association, nil)
-        end
-
-        it "returns an empty array" do
-          expect(fk).to be_empty
-        end
-      end
-
-      context "when provided an array of strings" do
-
-        context "when the strings are legal object ids" do
-
-          let(:object_id) do
-            BSON::ObjectId.new
-          end
-
-          let(:fk) do
-            Array.__mongoize_fk__(association, [ object_id.to_s ])
-          end
-
-          it "returns the object id in an array" do
-            expect(fk).to eq([ object_id ])
-          end
-        end
-
-        context "when the strings are not legal object ids" do
-
-          let(:string) do
-            "blah"
-          end
-
-          let(:fk) do
-            Array.__mongoize_fk__(association, [ string ])
-          end
-
-          it "returns the string in an array" do
-            expect(fk).to eq([ string ])
-          end
-        end
-
-        context "when the strings are blank" do
-
-          let(:fk) do
-            Array.__mongoize_fk__(association, [ "", "" ])
-          end
-
-          it "returns an empty array" do
-            expect(fk).to be_empty
-          end
-        end
-      end
-
-      context "when provided nils" do
-
-        let(:fk) do
-          Array.__mongoize_fk__(association, [ nil, nil, nil ])
-        end
-
-        it "returns an empty array" do
-          expect(fk).to be_empty
-        end
-      end
-    end
-  end
-
   describe "#__mongoize_time__" do
 
     let(:array) do
diff --git a/spec/mongoid/extensions/object_spec.rb b/spec/mongoid/extensions/object_spec.rb
index 80d313a3af..e610285798 100644
--- a/spec/mongoid/extensions/object_spec.rb
+++ b/spec/mongoid/extensions/object_spec.rb
@@ -30,97 +30,6 @@
     end
   end
 
-  describe ".__mongoize_fk__" do
-
-    context "when the related model uses object ids" do
-
-      let(:association) do
-        Game.relations["person"]
-      end
-
-      context "when provided an object id" do
-
-        let(:object_id) do
-          BSON::ObjectId.new
-        end
-
-        let(:fk) do
-          Object.__mongoize_fk__(association, object_id)
-        end
-
-        it "returns the object id" do
-          expect(fk).to eq(object_id)
-        end
-      end
-
-      context "when provided a string" do
-
-        context "when the string is a legal object id" do
-
-          let(:object_id) do
-            BSON::ObjectId.new
-          end
-
-          let(:fk) do
-            Object.__mongoize_fk__(association, object_id.to_s)
-          end
-
-          it "returns the object id" do
-            expect(fk).to eq(object_id)
-          end
-        end
-
-        context "when the string is not a legal object id" do
-
-          let(:string) do
-            "blah"
-          end
-
-          let(:fk) do
-            Object.__mongoize_fk__(association, string)
-          end
-
-          it "returns the string" do
-            expect(fk).to eq(string)
-          end
-        end
-
-        context "when the string is blank" do
-
-          let(:fk) do
-            Object.__mongoize_fk__(association, "")
-          end
-
-          it "returns nil" do
-            expect(fk).to be_nil
-          end
-        end
-      end
-
-      context "when provided nil" do
-
-        let(:fk) do
-          Object.__mongoize_fk__(association, nil)
-        end
-
-        it "returns nil" do
-          expect(fk).to be_nil
-        end
-      end
-
-      context "when provided an empty array" do
-
-        let(:fk) do
-          Object.__mongoize_fk__(association, [])
-        end
-
-        it "returns an empty array" do
-          expect(fk).to eq([])
-        end
-      end
-    end
-  end
-
   describe "#__mongoize_time__" do
 
     it "returns self" do
diff --git a/spec/mongoid/fields/foreign_key_spec.rb b/spec/mongoid/fields/foreign_key_spec.rb
index 3aafef65a5..15878a360c 100644
--- a/spec/mongoid/fields/foreign_key_spec.rb
+++ b/spec/mongoid/fields/foreign_key_spec.rb
@@ -716,4 +716,146 @@
       end
     end
   end
+
+  describe "#mongoize_foreign_key" do
+    let(:field) { described_class.new(:vals, type: Object, default: []) }
+    let(:association) { Person.relations['preferences'] }
+    subject(:mongoized) { field.send(:mongoize_foreign_key, type, association, object) }
+
+    context 'type is Array' do
+      let(:type) { Array }
+
+      context 'when the object is a BSON::ObjectId' do
+        let(:object) { BSON::ObjectId.new }
+
+        it 'returns the object id as an array' do
+          expect(mongoized).to eq([object])
+        end
+      end
+
+      context 'when the object is an Array of BSON::ObjectId' do
+        let(:object) { [BSON::ObjectId.new] }
+
+        it 'returns the object ids' do
+          expect(mongoized).to eq(object)
+        end
+      end
+
+      context 'when the object is a String which is a legal object id' do
+        let(:object) { BSON::ObjectId.new.to_s }
+
+        it 'returns the object id in an array' do
+          expect(mongoized).to eq([BSON::ObjectId.from_string(object)])
+        end
+      end
+
+      context 'when the object is a String which is not a legal object id' do
+        let(:object) { 'blah' }
+
+        it 'returns the object id in an array' do
+          expect(mongoized).to eq(%w[blah])
+        end
+      end
+
+      context 'when the object is a blank String' do
+        let(:object) { '' }
+
+        it 'returns an empty array' do
+          expect(mongoized).to eq([])
+        end
+      end
+
+      context 'when the object is nil' do
+        let(:object) { nil }
+
+        it 'returns an empty array' do
+          expect(mongoized).to eq([])
+        end
+      end
+
+      context 'when the object is Array of Strings which are legal object ids' do
+        let(:object) { [BSON::ObjectId.new.to_s] }
+
+        it 'returns the object id in an array' do
+          expect(mongoized).to eq([BSON::ObjectId.from_string(object.first)])
+        end
+      end
+
+      context 'when the object is Array of Strings which are not legal object ids' do
+        let(:object) { %w[blah] }
+
+        it 'returns the object id in an array' do
+          expect(mongoized).to eq(%w[blah])
+        end
+      end
+
+      context 'when the object is Array of Strings which are blank' do
+        let(:object) { ['', ''] }
+
+        it 'returns the object id in an array' do
+          expect(mongoized).to eq([])
+        end
+      end
+
+      context 'when the object is Array of nils' do
+          let(:object) { [nil, nil, nil] }
+
+          it 'returns the object id in an array' do
+            expect(mongoized).to eq([])
+          end
+        end
+    end
+
+    context 'type is not Array' do
+      let(:type) { Object }
+
+      context 'when the object is a BSON::ObjectId' do
+        let(:object) { BSON::ObjectId.new }
+
+        it 'returns the object id' do
+          expect(mongoized).to eq(object)
+        end
+      end
+
+      context 'when the object is a String which is a legal object id' do
+        let(:object) { BSON::ObjectId.new.to_s }
+
+        it 'returns the object id' do
+          expect(mongoized).to eq(BSON::ObjectId.from_string(object))
+        end
+      end
+
+      context 'when the object is a String which is not a legal object id' do
+        let(:object) { 'blah' }
+
+        it 'returns the string' do
+          expect(mongoized).to eq('blah')
+        end
+      end
+
+      context 'when the String is blank' do
+        let(:object) { '' }
+
+        it 'returns nil' do
+          expect(mongoized).to be_nil
+        end
+        end
+
+      context 'when the object is nil' do
+        let(:object) { '' }
+
+        it 'returns nil' do
+          expect(mongoized).to be_nil
+        end
+      end
+
+      context 'when object is an empty Array' do
+        let(:object) { [] }
+
+        it 'returns an empty array' do
+          expect(mongoized).to eq([])
+        end
+      end
+    end
+  end
 end

From b74ce466ac022ea65aee3de57ca486f47cc52eb0 Mon Sep 17 00:00:00 2001
From: johnnyshields <27655+johnnyshields@users.noreply.github.com>
Date: Tue, 5 Sep 2023 01:01:02 +0900
Subject: [PATCH 2/6] __mongoize_fk step 1: #mongoize_foreign_key should use
 class member variables

---
 lib/mongoid/fields/foreign_key.rb       | 12 +++++-------
 spec/mongoid/fields/foreign_key_spec.rb |  4 ++--
 2 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/lib/mongoid/fields/foreign_key.rb b/lib/mongoid/fields/foreign_key.rb
index 5e0b7f1df3..774acd9599 100644
--- a/lib/mongoid/fields/foreign_key.rb
+++ b/lib/mongoid/fields/foreign_key.rb
@@ -14,7 +14,7 @@ class ForeignKey < Standard
       # @example Add the atomic changes.
       #   field.add_atomic_changes(doc, "key", {}, [], [])
       #
-      # @todo: Durran: Refactor, big time.
+      # @todo: Refactor, big time.
       #
       # @param [ Document ] document The document to add to.
       # @param [ String ] name The name of the field.
@@ -95,7 +95,7 @@ def lazy?
       # @return [ Object ] The mongoized object.
       def mongoize(object)
         if type.resizable? || object_id_field?
-          mongoize_foreign_key(type, association, object)
+          mongoize_foreign_key(object)
         else
           related_id_field.mongoize(object)
         end
@@ -127,15 +127,13 @@ def resizable?
       # Convert the provided object to a foreign key, given the type
       # and metadata key constraint.
       #
-      # @example Convert the object to a fk.
-      #   mongoize_foreign_key(Array, association, object)
+      # @example Convert the object to a foreign key.
+      #   mongoize_foreign_key(object)
       #
-      # @param [ Class ] type The association metadata.
-      # @param [ Mongoid::Association::Relatable ] association The association metadata.
       # @param [ Object ] object The object to convert.
       #
       # @return [ Object ] The converted object.
-      def mongoize_foreign_key(type, association, object)
+      def mongoize_foreign_key(object)
         if type == Array
           if object.resizable?
             object.blank? ? object : association.convert_to_foreign_key(object)
diff --git a/spec/mongoid/fields/foreign_key_spec.rb b/spec/mongoid/fields/foreign_key_spec.rb
index 15878a360c..5357a57611 100644
--- a/spec/mongoid/fields/foreign_key_spec.rb
+++ b/spec/mongoid/fields/foreign_key_spec.rb
@@ -718,9 +718,9 @@
   end
 
   describe "#mongoize_foreign_key" do
-    let(:field) { described_class.new(:vals, type: Object, default: []) }
+    let(:field) { described_class.new(:vals, type: type, association: association) }
     let(:association) { Person.relations['preferences'] }
-    subject(:mongoized) { field.send(:mongoize_foreign_key, type, association, object) }
+    subject(:mongoized) { field.send(:mongoize_foreign_key, object) }
 
     context 'type is Array' do
       let(:type) { Array }

From dc6646b76996f0b83a46c6c766a9655cc11880ad Mon Sep 17 00:00:00 2001
From: johnnyshields <27655+johnnyshields@users.noreply.github.com>
Date: Tue, 5 Sep 2023 01:41:07 +0900
Subject: [PATCH 3/6] __mongoize_fk step 3: consolidate all specs to public
 #mongoize method

---
 lib/mongoid/fields/foreign_key.rb       |   2 +-
 spec/mongoid/fields/foreign_key_spec.rb | 480 ++++++++++++------------
 2 files changed, 251 insertions(+), 231 deletions(-)

diff --git a/lib/mongoid/fields/foreign_key.rb b/lib/mongoid/fields/foreign_key.rb
index 774acd9599..484b960af0 100644
--- a/lib/mongoid/fields/foreign_key.rb
+++ b/lib/mongoid/fields/foreign_key.rb
@@ -134,7 +134,7 @@ def resizable?
       #
       # @return [ Object ] The converted object.
       def mongoize_foreign_key(object)
-        if type == Array
+        if type == Array || type == Set
           if object.resizable?
             object.blank? ? object : association.convert_to_foreign_key(object)
           else
diff --git a/spec/mongoid/fields/foreign_key_spec.rb b/spec/mongoid/fields/foreign_key_spec.rb
index 5357a57611..fedfef3eca 100644
--- a/spec/mongoid/fields/foreign_key_spec.rb
+++ b/spec/mongoid/fields/foreign_key_spec.rb
@@ -497,230 +497,19 @@
     end
   end
 
-  describe "#mongoize" do
-
-    context "when the type is array" do
-
-      context "when the array is object ids" do
-
-        let(:association) do
-          Game.relations["person"]
-        end
-
-        let(:field) do
-          described_class.new(
-            :vals,
-            type: Array,
-            default: [],
-            identity: true,
-            association: association,
-            overwrite: true
-          )
-        end
-
-        context "when provided nil" do
-
-          it "returns an empty array" do
-            expect(field.mongoize(nil)).to be_empty
-          end
-        end
-
-        context "when provided an empty array" do
-
-          let(:array) do
-            []
-          end
-
-          it "returns an empty array" do
-            expect(field.mongoize(array)).to eq(array)
-          end
-
-          it "returns the same instance" do
-            expect(field.mongoize(array)).to equal(array)
-          end
-        end
-
-        context "when using object ids" do
-
-          let(:object_id) do
-            BSON::ObjectId.new
-          end
-
-          it "performs conversion on the ids if strings" do
-            expect(field.mongoize([object_id.to_s])).to eq([object_id])
-          end
-        end
-
-        context "when not using object ids" do
-
-          let(:object_id) do
-            BSON::ObjectId.new
-          end
-
-          before do
-            Person.field(
-              :_id,
-              type: String,
-              pre_processed: true,
-              default: ->{ BSON::ObjectId.new.to_s },
-              overwrite: true
-            )
-          end
-
-          after do
-            Person.field(
-              :_id,
-              type: BSON::ObjectId,
-              pre_processed: true,
-              default: ->{ BSON::ObjectId.new },
-              overwrite: true
-            )
-          end
-
-          it "does not convert" do
-            expect(field.mongoize([object_id.to_s])).to eq([object_id.to_s])
-          end
-        end
-      end
-    end
-
-    context "when the type is object" do
-
-      context "when the array is object ids" do
-
-        let(:association) do
-          Game.relations['person']
-        end
-
-        let(:field) do
-          described_class.new(
-            :vals,
-            type: Object,
-            default: nil,
-            identity: true,
-            association: association,
-            overwrite: true
-          )
-        end
-
-        context "when using object ids" do
-
-          let(:object_id) do
-            BSON::ObjectId.new
-          end
-
-          it "performs conversion on the ids if strings" do
-            expect(field.mongoize(object_id.to_s)).to eq(object_id)
-          end
-        end
-
-        context "when not using object ids" do
-
-          context "when using strings" do
-
-            context "when provided a string" do
-
-              let(:object_id) do
-                BSON::ObjectId.new
-              end
-
-              before do
-                Person.field(
-                  :_id,
-                  type: String,
-                  pre_processed: true,
-                  default: ->{ BSON::ObjectId.new.to_s },
-                  overwrite: true
-                )
-              end
-
-              after do
-                Person.field(
-                  :_id,
-                  type: BSON::ObjectId,
-                  pre_processed: true,
-                  default: ->{ BSON::ObjectId.new },
-                  overwrite: true
-                )
-              end
-
-              it "does not convert" do
-                expect(field.mongoize(object_id.to_s)).to eq(object_id.to_s)
-              end
-            end
-          end
-
-          context "when using integers" do
-
-            context "when provided a string" do
-
-              before do
-                Person.field(:_id, type: Integer, overwrite: true)
-              end
-
-              after do
-                Person.field(
-                  :_id,
-                  type: BSON::ObjectId,
-                  pre_processed: true,
-                  default: ->{ BSON::ObjectId.new },
-                  overwrite: true
-                )
-              end
-
-              it "converts the string to an integer" do
-                expect(field.mongoize("1")).to eq(1)
-              end
-            end
-          end
-        end
-      end
-    end
-  end
-
-  describe "#resizable" do
-
-    context "when the type is an array" do
-
-      let(:field) do
-        described_class.new(:vals, type: Array, default: [])
-      end
-
-      it "returns true" do
-        expect(field).to be_resizable
-      end
-    end
-
-    context "when the type is an object" do
-
-      let(:field) do
-        described_class.new(:vals, type: Object, default: [])
-      end
-
-      it "returns false" do
-        expect(field).to_not be_resizable
-      end
-    end
-  end
-
-  context "when the foreign key points is a many to many" do
-
-    context "when the related document stores non object ids" do
-
-      let(:agent) do
-        Agent.new(account_ids: [ true, false, 1, 2 ])
-      end
-
-      it "casts the ids on the initial set" do
-        expect(agent.account_ids).to eq([ "true", "false", "1", "2" ])
-      end
+  describe '#mongoize' do
+    let(:field) do
+      described_class.new(
+        :vals,
+        type: type,
+        default: [],
+        identity: true,
+        association: association,
+        overwrite: true
+      )
     end
-  end
-
-  describe "#mongoize_foreign_key" do
-    let(:field) { described_class.new(:vals, type: type, association: association) }
-    let(:association) { Person.relations['preferences'] }
-    subject(:mongoized) { field.send(:mongoize_foreign_key, object) }
+    let(:association) { Game.relations['person'] }
+    subject(:mongoized) { field.mongoize(object) }
 
     context 'type is Array' do
       let(:type) { Array }
@@ -784,7 +573,7 @@
       context 'when the object is Array of Strings which are not legal object ids' do
         let(:object) { %w[blah] }
 
-        it 'returns the object id in an array' do
+        it 'returns the Array' do
           expect(mongoized).to eq(%w[blah])
         end
       end
@@ -792,21 +581,133 @@
       context 'when the object is Array of Strings which are blank' do
         let(:object) { ['', ''] }
 
-        it 'returns the object id in an array' do
+        it 'returns an empty Array' do
           expect(mongoized).to eq([])
         end
       end
 
       context 'when the object is Array of nils' do
-          let(:object) { [nil, nil, nil] }
+        let(:object) { [nil, nil, nil] }
+
+        it 'returns an empty Array' do
+          expect(mongoized).to eq([])
+        end
+      end
+
+      context 'when the object is an empty Array' do
+        let(:object) { [] }
+
+        it 'returns an empty Array' do
+          expect(mongoized).to eq([])
+        end
+
+        it 'returns the same instance' do
+          expect(mongoized).to equal(object)
+        end
+      end
+
+      context 'when the object is a Set' do
+        let(:object) { Set['blah'] }
+
+        it 'returns the object id in an array' do
+          expect(mongoized).to eq(%w[blah])
+        end
+      end
+
+      context 'when foreign key is a String' do
+        before do
+          Person.field(:_id, type: String, overwrite: true)
+        end
+
+        after do
+          Person.field(
+            :_id,
+            type: BSON::ObjectId,
+            pre_processed: true,
+            default: ->{ BSON::ObjectId.new },
+            overwrite: true
+          )
+        end
+
+        context 'when the object is a String' do
+          let(:object) { %w[1] }
+
+          it 'returns String' do
+            expect(mongoized).to eq(object)
+          end
+        end
+
+        context 'when the object is a BSON::ObjectId' do
+          let(:object) { [BSON::ObjectId.new] }
+
+          it 'converts to String' do
+            expect(mongoized).to eq([object.first.to_s])
+          end
+        end
+
+        context 'when the object is an Integer' do
+          let(:object) { [1] }
+
+          it 'converts to String' do
+            expect(mongoized).to eq(%w[1])
+          end
+        end
+      end
+
+      context 'when foreign key is an Integer' do
+        before do
+          Person.field(:_id, type: Integer, overwrite: true)
+        end
+
+        after do
+          Person.field(
+            :_id,
+            type: BSON::ObjectId,
+            pre_processed: true,
+            default: ->{ BSON::ObjectId.new },
+            overwrite: true
+          )
+        end
+
+        context 'when the object is a String' do
+          let(:object) { %w[1] }
 
-          it 'returns the object id in an array' do
-            expect(mongoized).to eq([])
+          it 'converts to Integer' do
+            expect(mongoized).to eq([1])
           end
         end
+
+        context 'when the object is an Integer' do
+          let(:object) { [1] }
+
+          it 'returns Integer' do
+            expect(mongoized).to eq([1])
+          end
+        end
+      end
     end
 
-    context 'type is not Array' do
+    context 'type is Set' do
+      let(:type) { Set }
+
+      context 'when the object is an Array of BSON::ObjectId' do
+        let(:object) { [BSON::ObjectId.new] }
+
+        it 'returns the object ids' do
+          expect(mongoized).to eq(object)
+        end
+      end
+
+      context 'when the object is a Set of BSON::ObjectId' do
+        let(:object) { Set[BSON::ObjectId.new] }
+
+        it 'returns the object id in an array' do
+          expect(mongoized).to eq([object.first])
+        end
+      end
+    end
+
+    context 'type is Object' do
       let(:type) { Object }
 
       context 'when the object is a BSON::ObjectId' do
@@ -839,7 +740,7 @@
         it 'returns nil' do
           expect(mongoized).to be_nil
         end
-        end
+      end
 
       context 'when the object is nil' do
         let(:object) { '' }
@@ -856,6 +757,125 @@
           expect(mongoized).to eq([])
         end
       end
+
+      context 'when the object is a Set' do
+        let(:object) { Set['blah'] }
+
+        it 'returns the set' do
+          expect(mongoized).to eq(Set['blah'])
+        end
+      end
+
+      context 'when foreign key is a String' do
+        before do
+          Person.field(:_id, type: String, overwrite: true)
+        end
+
+        after do
+          Person.field(
+            :_id,
+            type: BSON::ObjectId,
+            pre_processed: true,
+            default: ->{ BSON::ObjectId.new },
+            overwrite: true
+          )
+        end
+
+        context 'when the object is a String' do
+          let(:object) { '1' }
+
+          it 'returns String' do
+            expect(mongoized).to eq(object)
+          end
+        end
+
+        context 'when the object is a BSON::ObjectId' do
+          let(:object) { BSON::ObjectId.new }
+
+          it 'converts to String' do
+            expect(mongoized).to eq(object.to_s)
+          end
+        end
+
+        context 'when the object is an Integer' do
+          let(:object) { 1 }
+
+          it 'converts to String' do
+            expect(mongoized).to eq('1')
+          end
+        end
+      end
+
+      context 'when foreign key is an Integer' do
+        before do
+          Person.field(:_id, type: Integer, overwrite: true)
+        end
+
+        after do
+          Person.field(
+            :_id,
+            type: BSON::ObjectId,
+            pre_processed: true,
+            default: ->{ BSON::ObjectId.new },
+            overwrite: true
+          )
+        end
+
+        context 'when the object is a String' do
+          let(:object) { '1' }
+
+          it 'converts to Integer' do
+            expect(mongoized).to eq(1)
+          end
+        end
+
+        context 'when the object is an Integer' do
+          let(:object) { 1 }
+
+          it 'returns Integer' do
+            expect(mongoized).to eq(object)
+          end
+        end
+      end
+    end
+  end
+
+  describe "#resizable" do
+
+    context "when the type is an array" do
+
+      let(:field) do
+        described_class.new(:vals, type: Array, default: [])
+      end
+
+      it "returns true" do
+        expect(field).to be_resizable
+      end
+    end
+
+    context "when the type is an object" do
+
+      let(:field) do
+        described_class.new(:vals, type: Object, default: [])
+      end
+
+      it "returns false" do
+        expect(field).to_not be_resizable
+      end
+    end
+  end
+
+  context "when the foreign key points is a many to many" do
+
+    context "when the related document stores non object ids" do
+
+      let(:agent) do
+        Agent.new(account_ids: [ true, false, 1, 2 ])
+      end
+
+      it "casts the ids on the initial set" do
+        expect(agent.account_ids).to eq([ "true", "false", "1", "2" ])
+      end
     end
   end
 end

From 88fce3ac9665117c97a5f04c6f0333ee7721acf0 Mon Sep 17 00:00:00 2001
From: Johnny Shields <27655+johnnyshields@users.noreply.github.com>
Date: Tue, 5 Sep 2023 01:48:15 +0900
Subject: [PATCH 4/6] Update foreign_key.rb

---
 lib/mongoid/fields/foreign_key.rb | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/lib/mongoid/fields/foreign_key.rb b/lib/mongoid/fields/foreign_key.rb
index 484b960af0..2b8b558a90 100644
--- a/lib/mongoid/fields/foreign_key.rb
+++ b/lib/mongoid/fields/foreign_key.rb
@@ -124,8 +124,7 @@ def resizable?
 
       private
 
-      # Convert the provided object to a foreign key, given the type
-      # and metadata key constraint.
+      # Convert the provided object to a Mongo-friendly foreign key.
       #
       # @example Convert the object to a foreign key.
       #   mongoize_foreign_key(object)

From a3e295ba845c9bff729925e1a85119261ef40a29 Mon Sep 17 00:00:00 2001
From: Jamis Buck <jamis.buck@mongodb.com>
Date: Wed, 8 Nov 2023 09:19:08 -0700
Subject: [PATCH 5/6] deprecate, rather than remove

---
 lib/mongoid/extensions/array.rb  | 19 +++++++++++++++++++
 lib/mongoid/extensions/object.rb |  2 ++
 2 files changed, 21 insertions(+)

diff --git a/lib/mongoid/extensions/array.rb b/lib/mongoid/extensions/array.rb
index cf5cf0656a..6ff0d75c51 100644
--- a/lib/mongoid/extensions/array.rb
+++ b/lib/mongoid/extensions/array.rb
@@ -105,6 +105,25 @@ def resizable?
 
       module ClassMethods
 
+        # Convert the provided object to a proper array of foreign keys.
+        #
+        # @example Mongoize the object.
+        #   Array.__mongoize_fk__(constraint, object)
+        #
+        # @param [ Mongoid::Association::Relatable ] association The association metadata.
+        # @param [ Object ] object The object to convert.
+        #
+        # @return [ Array ] The array of ids.
+        # @deprecated
+        def __mongoize_fk__(association, object)
+          if object.resizable?
+            object.blank? ? object : association.convert_to_foreign_key(object)
+          else
+            object.blank? ? [] : association.convert_to_foreign_key(Array(object))
+          end
+        end
+        Mongoid.deprecate(self, :__mongoize_fk__)
+
         # Turn the object from the ruby type we deal with to a Mongo friendly
         # type.
         #
diff --git a/lib/mongoid/extensions/object.rb b/lib/mongoid/extensions/object.rb
index 495f7b2c40..879602f39e 100644
--- a/lib/mongoid/extensions/object.rb
+++ b/lib/mongoid/extensions/object.rb
@@ -215,10 +215,12 @@ module ClassMethods
         # @param [ Object ] object The object to convert.
         #
         # @return [ Object ] The converted object.
+        # @deprecated
         def __mongoize_fk__(association, object)
           return nil if !object || object == ""
           association.convert_to_foreign_key(object)
         end
+        Mongoid.deprecate(self, :__mongoize_fk__)
 
         # Convert the object from its mongo friendly ruby type to this type.
         #

From 7aebf023710c1744dfff4953177d9baabefd3174 Mon Sep 17 00:00:00 2001
From: Jamis Buck <jamis.buck@mongodb.com>
Date: Wed, 8 Nov 2023 13:19:00 -0700
Subject: [PATCH 6/6] Set support requires a bit of baby-sitting...

---
 lib/mongoid/fields/foreign_key.rb | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/mongoid/fields/foreign_key.rb b/lib/mongoid/fields/foreign_key.rb
index 2b8b558a90..815d5cdc99 100644
--- a/lib/mongoid/fields/foreign_key.rb
+++ b/lib/mongoid/fields/foreign_key.rb
@@ -134,6 +134,8 @@ def resizable?
       # @return [ Object ] The converted object.
       def mongoize_foreign_key(object)
         if type == Array || type == Set
+          object = object.to_a if type == Set || object.is_a?(Set)
+
           if object.resizable?
             object.blank? ? object : association.convert_to_foreign_key(object)
           else