Add test for nested list decoding and improve ListEncoderDecoder

Co-authored-by: ipetrov <[email protected]>

Author: cursoragent

DSPythonNet3/DSPythonNet3.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 	<PropertyGroup>
 		<ProjectGuid>{F1541C2D-80A9-4FE7-8D9E-75A8B9FF3479}</ProjectGuid>
 		<OutputType>Library</OutputType>
@@ -10,6 +10,7 @@
 	<ItemGroup>
 		<InternalsVisibleTo Include="PythonMigrationViewExtension" />
 		<InternalsVisibleTo Include="DynamoPythonTests" />
+		<InternalsVisibleTo Include="DSPythonNet3Tests" />
 
 		<PackageReference Include="DynamoVisualProgramming.Core" Version="$(DynamoPackageVersion)" ExcludeAssets="runtime" />
 		<PackageReference Include="DynamoVisualProgramming.DynamoServices" Version="$(DynamoPackageVersion)" ExcludeAssets="runtime" />

DSPythonNet3/Encoders/ListEncodeDecoder.cs

@@ -28,18 +28,18 @@ public bool TryDecode<T>(PyObject pyObj, out T value)
                 return false;
             }
 
-            using (var pyList = PyList.AsList(pyObj))
+            if (typeof(T).IsGenericType)
             {
-                if (typeof(T).IsGenericType)
+                using (var pyList = PyList.AsList(pyObj))
                 {
                     value = pyList.ToList<T>();
                 }
-                else
-                {
-                    value = (T)pyList.ToList();
-                }
                 return true;
             }
+
+            var converted = ConvertToArrayList(pyObj);
+            value = (T)converted;
+            return true;
         }
 
         public PyObject TryEncode(object value)
@@ -57,5 +57,54 @@ bool IPyObjectDecoder.CanDecode(PyType objectType, Type targetType)
             }
             return decodableTypes.IndexOf(targetType) >= 0;
         }
+
+        private static IList ConvertToArrayList(PyObject pyObj)
+        {
+            using var pyList = PyList.AsList(pyObj);
+            var result = new ArrayList();
+            foreach (PyObject item in pyList)
+            {
+                using (item)
+                {
+                    result.Add(ConvertItem(item));
+                }
+            }
+
+            return result;
+        }
+
+        private static object ConvertItem(PyObject item)
+        {
+            if (TryGetClrObject(item, out var clrObject))
+            {
+                return clrObject;
+            }
+
+            if (PyString.IsStringType(item))
+            {
+                return item.AsManagedObject(typeof(string));
+            }
+
+            if (PyList.IsListType(item) || PyTuple.IsTupleType(item))
+            {
+                return ConvertToArrayList(item);
+            }
+
+            return item.AsManagedObject(typeof(object));
+        }
+
+        private static bool TryGetClrObject(PyObject pyObj, out object clrObject)
+        {
+            try
+            {
+                clrObject = pyObj.GetManagedObject();
+                return true;
+            }
+            catch
+            {
+                clrObject = null;
+                return false;
+            }
+        }
     }
 }

DSpythonNet3Tests/ListEncoderDecoderTests.cs

@@ -0,0 +1,47 @@
+using System.Collections;
+using DSPythonNet3;
+using DSPythonNet3.Encoders;
+using NUnit.Framework;
+using Python.Runtime;
+
+namespace DSPythonNet3Tests
+{
+    public class ListEncoderDecoderTests
+    {
+        [Test]
+        public void TryDecode_ConvertsNestedPythonListsToClrLists()
+        {
+            DSPythonNet3Evaluator.InitializePython();
+
+            using (Py.GIL())
+            using (var scope = Py.CreateScope())
+            {
+                scope.Exec("value = [[1, [2, 3]], ['a', ['b']]]");
+                using var pyList = scope.Get("value");
+
+                var decoder = new ListEncoderDecoder();
+                var success = decoder.TryDecode(pyList, out IList result);
+
+                Assert.That(success, Is.True);
+                Assert.That(result, Is.InstanceOf<IList>());
+
+                var first = result[0] as IList;
+                Assert.That(first, Is.Not.Null);
+                Assert.That(first[0], Is.EqualTo(1));
+
+                var secondLevel = first?[1] as IList;
+                Assert.That(secondLevel, Is.Not.Null);
+                Assert.That(secondLevel?[0], Is.EqualTo(2));
+                Assert.That(secondLevel?[1], Is.EqualTo(3));
+
+                var second = result[1] as IList;
+                Assert.That(second, Is.Not.Null);
+                Assert.That(second?[0], Is.EqualTo("a"));
+
+                var thirdLevel = second?[1] as IList;
+                Assert.That(thirdLevel, Is.Not.Null);
+                Assert.That(thirdLevel?[0], Is.EqualTo("b"));
+            }
+        }
+    }
+}