Merge remote-tracking branch 'origin/vnext' into dm/commandline

Author: darrelmiller

src/Microsoft.OpenApi/Models/OpenApiSchema.cs

@@ -442,13 +442,25 @@ internal void SerializeAsV2(
                 throw Error.ArgumentNull(nameof(writer));
             }
 
-            
-            if (Reference != null && writer.GetSettings().ReferenceInline != ReferenceInlineSetting.InlineLocalReferences)
+            if (Reference != null)
             {
-                Reference.SerializeAsV2(writer);
-                return;
+                var settings = writer.GetSettings();
+                if (settings.ReferenceInline != ReferenceInlineSetting.InlineLocalReferences)
+                {
+                    Reference.SerializeAsV2(writer);
+                    return;
+                }
+
+                // If Loop is detected then just Serialize as a reference.
+                if (!settings.LoopDetector.PushLoop<OpenApiSchema>(this))
+                {
+                    settings.LoopDetector.SaveLoop(this);
+                    Reference.SerializeAsV3(writer);
+                    return;
+                }
             }
 
+
             if (parentRequiredProperties == null)
             {
                 parentRequiredProperties = new HashSet<string>();