fix: v2 references for properties do not work as expected

src/Microsoft.OpenApi/Models/OpenApiSchema.cs

@@ -650,7 +650,7 @@ internal void WriteAsItemsProperties(IOpenApiWriter writer)
         /// <param name="writer">The open api writer.</param>
         /// <param name="parentRequiredProperties">The list of required properties in parent schema.</param>
         /// <param name="propertyName">The property name that will be serialized.</param>
-        internal void SerializeAsV2(
+        internal virtual void SerializeAsV2(
             IOpenApiWriter writer,
             ISet<string> parentRequiredProperties,
             string propertyName)

src/Microsoft.OpenApi/Models/References/OpenApiSchemaReference.cs

@@ -227,6 +227,22 @@ public override void SerializeAsV3(IOpenApiWriter writer)
             writer.GetSettings().LoopDetector.PopLoop<OpenApiSchema>();
         }
 
+        /// <inheritdoc/>
+        internal override void SerializeAsV2(
+            IOpenApiWriter writer,
+            ISet<string> parentRequiredProperties,
+            string propertyName)
+        {
+            if (!writer.GetSettings().ShouldInlineReference(_reference))
+            {
+                _reference.SerializeAsV2(writer);
+            }
+            else
+            {
+                base.SerializeAsV2(writer, parentRequiredProperties, propertyName);
+            }
+        }
+
         /// <inheritdoc/>
         public override void SerializeAsV2(IOpenApiWriter writer)
         {

test/Microsoft.OpenApi.Readers.Tests/V2Tests/OpenApiSchemaTests.cs

@@ -11,6 +11,8 @@
 using System.Text.Json.Nodes;
 using System.Collections.Generic;
 using FluentAssertions.Equivalency;
+using Microsoft.OpenApi.Models.References;
+using Microsoft.OpenApi.Writers;
 
 namespace Microsoft.OpenApi.Readers.Tests.V2Tests
 {
@@ -95,5 +97,56 @@ public void ParseSchemaWithEnumShouldSucceed()
                               .Excluding((IMemberInfo memberInfo) =>
                                     memberInfo.Path.EndsWith("Parent")));
         }
+        [Fact]
+        public void PropertiesReferenceShouldWork()
+        {
+            var workingDocument = new OpenApiDocument()
+            {
+                Components = new OpenApiComponents(),
+            };
+            const string referenceId = "targetSchema";
+            var targetSchema = new OpenApiSchema()
+            {
+                Type = JsonSchemaType.Object,
+                Properties = new Dictionary<string, OpenApiSchema>
+                {
+                    ["prop1"] = new OpenApiSchema()
+                    {
+                        Type = JsonSchemaType.String
+                    }
+                }
+            };
+            workingDocument.Components.Schemas.Add(referenceId, targetSchema);
+            workingDocument.Workspace.RegisterComponents(workingDocument);
+            var referenceSchema = new OpenApiSchema()
+            {
+                Type = JsonSchemaType.Object,
+                Properties = new Dictionary<string, OpenApiSchema>
+                {
+                    ["propA"] = new OpenApiSchemaReference(referenceId, workingDocument),
+                }
+            };
+
+            using var textWriter = new StringWriter();
+            var writer = new OpenApiJsonWriter(textWriter);
+            referenceSchema.SerializeAsV2(writer);
+
+            var json = textWriter.ToString();
+            var expected = JsonNode.Parse(
+                """
+                {
+                    "type": "object",
+                    "properties":
+                    {
+                        "propA":
+                        {
+                            "$ref": "#/definitions/targetSchema"
+                        }
+                    }
+                }
+                """
+            );
+            Assert.True(JsonNode.DeepEquals(JsonNode.Parse(json), expected));
+        }
     }
 }