DYN-10248: Fix crash when opening the Python Migration Assistant on an IronPython2 node

src/PythonMigrationViewExtension/MigrationAssistant/PythonMigrationAssistantViewModel.cs

@@ -24,6 +24,7 @@ internal class PythonMigrationAssistantViewModel : NotificationObject
         private readonly Version dynamoVersion;
         private PythonNode PythonNode;
 
+        private readonly Func<string, string> codeConverter;
         private IDiffViewViewModel currentViewModel;
         private SideBySideDiffModel diffModel;
 
@@ -43,27 +44,47 @@ public IDiffViewViewModel CurrentViewModel
             set { this.currentViewModel = value; RaisePropertyChanged(nameof(this.CurrentViewModel)); }
         }
 
-        public PythonMigrationAssistantViewModel(PythonNode pythonNode, WorkspaceModel workspace, IPathManager pathManager, Version dynamoVersion)
+        /// <summary>
+        /// Initializes the view model, runs the 2-to-3 code migration, and prepares the diff model.
+        /// If migration fails the view model is placed in an error state rather than propagating the exception.
+        /// </summary>
+        /// <param name="pythonNode">The Python node whose script will be migrated.</param>
+        /// <param name="workspace">The workspace that contains the node.</param>
+        /// <param name="pathManager">Provides backup and application paths.</param>
+        /// <param name="dynamoVersion">The running Dynamo version, used to scope disclaimer-dismiss files.</param>
+        /// <param name="codeConverter">
+        /// Optional override for the migration function. Defaults to <see cref="ScriptMigrator.MigrateCode"/>.
+        /// Intended for unit testing only.
+        /// </param>
+        public PythonMigrationAssistantViewModel(PythonNode pythonNode, WorkspaceModel workspace, IPathManager pathManager, Version dynamoVersion, Func<string, string> codeConverter = null)
         {
             PythonNode = pythonNode;
             OldCode = pythonNode.Script;
 
             this.workspace = workspace;
             backupDirectory = pathManager.BackupDirectory;
             this.dynamoVersion = dynamoVersion;
+            this.codeConverter = codeConverter;
 
             try
             {
                 MigrateCode();
             }
             catch (PythonException)
             {
-                var sidebyside = new SideBySideDiffBuilder();
-                diffModel = sidebyside.BuildDiffModel(OldCode, OldCode, false);
-
-                SetSideBySideViewModel();
-
-                CurrentViewModel.DiffState = State.Error;
+                // Python script error during migration (e.g. syntax the 2to3 tool cannot parse).
+                SetMigrationErrorState();
+                return;
+            }
+            catch (Exception ex) when (
+                ex is TypeLoadException ||
+                ex is MissingMethodException ||
+                ex is FileLoadException ||
+                ex is BadImageFormatException)
+            {
+                // Python.Runtime assembly at runtime is incompatible (e.g. pythonnet 2.x instead of 3.x).
+                // Types or members such as PyModule may be absent in older assemblies.
+                SetMigrationErrorState();
                 return;
             }
             SetSideBySideViewModel();
@@ -74,12 +95,21 @@ public PythonMigrationAssistantViewModel(PythonNode pythonNode, WorkspaceModel w
 
         private void MigrateCode()
         {
-            NewCode = ScriptMigrator.MigrateCode(OldCode);
+            var converter = codeConverter ?? ScriptMigrator.MigrateCode;
+            NewCode = converter(OldCode);
 
             var sidebyside = new SideBySideDiffBuilder();
             diffModel = sidebyside.BuildDiffModel(OldCode, NewCode, false);
         }
 
+        private void SetMigrationErrorState()
+        {
+            var sidebyside = new SideBySideDiffBuilder();
+            diffModel = sidebyside.BuildDiffModel(OldCode, OldCode, false);
+            SetSideBySideViewModel();
+            CurrentViewModel.DiffState = State.Error;
+        }
+
         /// <summary>
         /// Replaces the code in the Python node with the code changes made by the Migration Assistant.
         /// </summary>

test/Libraries/DynamoPythonTests/PythonMigrationAssistantViewModelTests.cs

@@ -0,0 +1,119 @@
+using System;
+using System.IO;
+using Dynamo;
+using Dynamo.Graph.Workspaces;
+using Dynamo.PythonMigration.Differ;
+using Dynamo.PythonMigration.MigrationAssistant;
+using NUnit.Framework;
+using PythonNodeModels;
+
+namespace DynamoPythonTests
+{
+    [TestFixture]
+    public class PythonMigrationAssistantViewModelTests : DynamoModelTestBase
+    {
+        /// <summary>
+        /// Regression test: when Python.Runtime is an incompatible version (e.g. pythonnet 2.x loaded
+        /// instead of 3.x), Py.CreateScope() throws TypeLoadException because PyModule does not exist
+        /// in that assembly. The ViewModel must catch this and show an error state rather than crashing.
+        /// </summary>
+        [Test]
+        public void WhenMigrationThrowsTypeLoadExceptionViewModelShowsErrorState()
+        {
+            // Arrange
+            var pyNode = new PythonNode();
+            var workspace = CurrentDynamoModel.CurrentWorkspace as WorkspaceModel;
+            var pathManager = CurrentDynamoModel.PathManager;
+
+            Func<string, string> brokenMigrator = _ =>
+                throw new TypeLoadException("Could not load type 'Python.Runtime.PyModule' from assembly 'Python.Runtime, Version=2.5.2.12086'");
+
+            // Act
+            PythonMigrationAssistantViewModel viewModel = null;
+            Assert.DoesNotThrow(() =>
+            {
+                viewModel = new PythonMigrationAssistantViewModel(
+                    pyNode, workspace, pathManager, new Version(3, 0), brokenMigrator);
+            });
+
+            // Assert
+            Assert.IsNotNull(viewModel);
+            Assert.AreEqual(State.Error, viewModel.CurrentViewModel.DiffState);
+        }
+
+        /// <summary>
+        /// Verifies that a MissingMethodException (e.g. missing member in incompatible Python.Runtime)
+        /// during migration is handled gracefully and shows an error state.
+        /// </summary>
+        [Test]
+        public void WhenMigrationThrowsMissingMethodExceptionViewModelShowsErrorState()
+        {
+            var pyNode = new PythonNode();
+            var workspace = CurrentDynamoModel.CurrentWorkspace as WorkspaceModel;
+            var pathManager = CurrentDynamoModel.PathManager;
+
+            Func<string, string> brokenMigrator = _ =>
+                throw new MissingMethodException("Python.Runtime.Py", "CreateScope");
+
+            PythonMigrationAssistantViewModel viewModel = null;
+            Assert.DoesNotThrow(() =>
+            {
+                viewModel = new PythonMigrationAssistantViewModel(
+                    pyNode, workspace, pathManager, new Version(3, 0), brokenMigrator);
+            });
+
+            Assert.IsNotNull(viewModel);
+            Assert.AreEqual(State.Error, viewModel.CurrentViewModel.DiffState);
+        }
+
+        /// <summary>
+        /// Verifies that a FileLoadException (e.g. assembly version conflict) during migration
+        /// is handled gracefully and shows an error state.
+        /// </summary>
+        [Test]
+        public void WhenMigrationThrowsFileLoadExceptionViewModelShowsErrorState()
+        {
+            var pyNode = new PythonNode();
+            var workspace = CurrentDynamoModel.CurrentWorkspace as WorkspaceModel;
+            var pathManager = CurrentDynamoModel.PathManager;
+
+            Func<string, string> brokenMigrator = _ =>
+                throw new FileLoadException("Could not load file or assembly 'Python.Runtime'");
+
+            PythonMigrationAssistantViewModel viewModel = null;
+            Assert.DoesNotThrow(() =>
+            {
+                viewModel = new PythonMigrationAssistantViewModel(
+                    pyNode, workspace, pathManager, new Version(3, 0), brokenMigrator);
+            });
+
+            Assert.IsNotNull(viewModel);
+            Assert.AreEqual(State.Error, viewModel.CurrentViewModel.DiffState);
+        }
+
+        /// <summary>
+        /// Verifies that a BadImageFormatException (e.g. 32/64-bit or .NET target mismatch in
+        /// Python.Runtime) during migration is handled gracefully and shows an error state.
+        /// </summary>
+        [Test]
+        public void WhenMigrationThrowsBadImageFormatExceptionViewModelShowsErrorState()
+        {
+            var pyNode = new PythonNode();
+            var workspace = CurrentDynamoModel.CurrentWorkspace as WorkspaceModel;
+            var pathManager = CurrentDynamoModel.PathManager;
+
+            Func<string, string> brokenMigrator = _ =>
+                throw new BadImageFormatException("The format of the file 'Python.Runtime' is invalid.");
+
+            PythonMigrationAssistantViewModel viewModel = null;
+            Assert.DoesNotThrow(() =>
+            {
+                viewModel = new PythonMigrationAssistantViewModel(
+                    pyNode, workspace, pathManager, new Version(3, 0), brokenMigrator);
+            });
+
+            Assert.IsNotNull(viewModel);
+            Assert.AreEqual(State.Error, viewModel.CurrentViewModel.DiffState);
+        }
+    }
+}