fix on-fly swap from recursive to iterative cloning

Author: lofcz

FastCloner.Tests/DynamicMaxRecursionDepthTests.cs

@@ -0,0 +1,123 @@
+namespace FastCloner.Tests;
+
+[TestFixture]
+public class DynamicMaxRecursionDepthTests
+{
+    public class A
+    {
+        public List<B> Bs = [];
+        public B? Child;
+    }
+
+    public class B
+    {
+        public A? Child;
+    }
+    
+    [OneTimeSetUp]
+    public void BaseOneTimeSetUp()
+    {
+        
+    }
+
+    [OneTimeTearDown]
+    public void BaseOneTimeTearDown()
+    {
+        FastCloner.MaxRecursionDepth = 1000;
+    }
+
+    [Test]
+    public void TestDynamicMaxRecursionDepth()
+    {
+        // Arrange
+        A orig = new A();
+        orig.Bs.Add(new B());
+
+        // Act & Assert: MRD = 1
+        {
+            FastCloner.MaxRecursionDepth = 1;
+            A? clone = FastCloner.DeepClone(orig);
+            AssertClone(clone);
+        }
+        
+        // Act & Assert: MRD = 2
+        {
+            FastCloner.MaxRecursionDepth = 2;
+            A? clone = FastCloner.DeepClone(orig);
+            AssertClone(clone);
+        }
+        
+        // Act & Assert: MRD = 3
+        {
+            FastCloner.MaxRecursionDepth = 3;
+            A? clone = FastCloner.DeepClone(orig);
+            AssertClone(clone);
+        }
+
+        void AssertClone(A? clone)
+        {
+            using (Assert.EnterMultipleScope())
+            {
+                Assert.That((orig == clone).Dump(), Is.EqualTo("false"), $"Orig should not be the same as clone for depth {FastCloner.MaxRecursionDepth}");
+                Assert.That((orig.Bs == clone.Bs).Dump(), Is.EqualTo("false"), $"Orig.Bs should not be the same as clone.Bs for depth {FastCloner.MaxRecursionDepth}");
+                Assert.That((orig.Bs.First() == clone.Bs.First()).Dump(), Is.EqualTo("false"), $"Orig.Bs.First() should not be the same as clone.Bs.First() for depth {FastCloner.MaxRecursionDepth}");
+            }
+        }
+    }
+
+    [Test]
+    public void TestDeepObjectGraph_1500Levels_WithMRD1000()
+    {
+        // Arrange
+        const int nestLevel = 1500;
+        const int maxRecursionDepth = 1000;
+        
+        A root = new A();
+        A currentA = root;
+        
+        for (int i = 0; i < nestLevel; i++)
+        {
+            B newB = new B();
+            currentA.Child = newB;
+            
+            if (i < nestLevel - 1)
+            {
+                A newA = new A();
+                newB.Child = newA;
+                currentA = newA;
+            }
+        }
+        
+        // Act
+        FastCloner.MaxRecursionDepth = maxRecursionDepth;
+        A? clone = FastCloner.DeepClone(root);
+        
+        // Assert
+        Assert.That(clone, Is.Not.Null);
+        Assert.That((root == clone).Dump(), Is.EqualTo("false"));
+        
+        A? origA = root;
+        A? clonedA = clone;
+        int level = 0;
+        
+        while (origA != null && clonedA != null)
+        {
+            Assert.That((origA == clonedA).Dump(), Is.EqualTo("false"), $"A at level {level} should be different objects");
+            
+            if (origA.Child != null && clonedA.Child != null)
+            {
+                Assert.That((origA.Child == clonedA.Child).Dump(), Is.EqualTo("false"), $"B at level {level} should be different objects");
+                
+                origA = origA.Child.Child;
+                clonedA = clonedA.Child.Child;
+                level++;
+            }
+            else
+            {
+                break;
+            }
+        }
+        
+        Assert.That(level, Is.GreaterThan(maxRecursionDepth), $"Verified {level} levels");
+    }
+}

FastCloner.Tests/FastCloner.Tests.csproj

@@ -25,6 +25,7 @@
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>
+    <PackageReference Include="ObjectDumper.NET" Version="4.3.4-pre" />
     <PackageReference Include="System.Data.SqlClient" Version="4.9.0" />
     <PackageReference Include="System.Data.SQLite.Core" Version="1.0.119" />
     <PackageReference Include="System.Drawing.Common" Version="8.0.3" />

FastCloner/Code/FastClonerGenerator.cs

@@ -81,6 +81,8 @@ internal static class FastClonerGenerator
             UseWorkList = TypeHasDirectSelfReference(rootType)
         };
 
+        object result;
+        
         if (!state.UseWorkList)
         {
             try
@@ -91,12 +93,18 @@ internal static class FastClonerGenerator
                 {
                     state.DecrementDepth();
                     state.UseWorkList = true;
+                    result = cloner(obj, state);
                 }
                 else
                 {
-                    object resultNormal = cloner(obj, state);
+                    result = cloner(obj, state);
                     state.DecrementDepth();
-                    return resultNormal;
+                    
+                    // if UseWorkList was set during recursive cloning, process the worklist
+                    if (!state.UseWorkList)
+                    {
+                        return result;
+                    }
                 }
             }
             catch
@@ -105,8 +113,11 @@ internal static class FastClonerGenerator
                 throw;
             }
         }
-
-        object result = cloner(obj, state);
+        else
+        {
+            result = cloner(obj, state);
+        }
+        
         while (state.TryPop(out object from, out object to, out Type type))
         {
             // boxed value types - MemberwiseClone already created a value copy.