Studio Pro crashes when opening Changes details after `ALTER ENTITY ... MODIFY ATTRIBUTE`

[savinocannonebiz]

After changing the type of an existing entity attribute with ALTER ENTITY ... MODIFY ATTRIBUTE, Mendix Studio Pro displays the change in the Changes panel. However, double-clicking the change to open its details causes Studio Pro to enter an exception state.

The affected domain model remains accessible, and the updated attribute type is visible in the Domain Model editor.

Reproduction Steps

1. Existing Mendix project started from 10.x and currently in 11.12.4, example name NorthwindForge.
2. Use a module such as AuroraPlanning.
3. Have (or create) a non-persistent entity named ShipmentMaterialDto with an attribute:
   • MaterialCode: String(unlimited)
4. Apply the following MDL change:

ALTER ENTITY AuroraPlanning."ShipmentMaterialDto"
  MODIFY ATTRIBUTE "MaterialCode" String(255);

5. Validate and execute the MDL with mxcli.
6. Open the project in Mendix Studio Pro.
7. Open the Domain Model and confirm that MaterialCode is now String(unlimited).
8. Open the Changes panel.
9. Double-click the domain model change to view its details.

Expected Behavior

Studio Pro should display the details of the changed attribute, including the old and new string length.

Actual Behavior

The change is shown in the Changes panel, but opening its details causes an exception. The relevant part of the exception is:

System.InvalidOperationException:
Objects with ID [redacted] of type DomainModels$NoGeneralization
do not have the same properties.

baseNames = HasChangedByAttr, HasChangedDateAttr,
HasCreatedDateAttr, HasOwnerAttr, Persistable;

newNames = Persistable

The stack trace includes:

System.InvalidOperationException: Objects with ID a884c3e2-c7f9-596c-9015-5cc0aed512c3 of type DomainModels$NoGeneralization do not have the same properties. baseNames = HasChangedByAttr, HasChangedDateAttr, HasCreatedDateAttr, HasOwnerAttr, Persistable; newNames = Persistable
   at Mendix.Modeler.MergeLib.ContentsAlgorithmNewStyle.DifferenceComputer.CompareObjects(MprObject baseObject, MprObject newObject) in Mendix.Modeler.MergeLib\ContentsAlgorithmNewStyle\DifferenceComputer.cs:line 48
   at Mendix.Modeler.MergeLib.ContentsAlgorithmNewStyle.DifferenceComputer.ComputeDifferences() in Mendix.Modeler.MergeLib\ContentsAlgorithmNewStyle\DifferenceComputer.cs:line 32
   at Mendix.Modeler.DiffLib.DifferencesRenderer.GetModificationRows() in Mendix.Modeler.DiffLib\DifferencesRenderer.cs:line 26
   at Mendix.Modeler.VersionControl.Status.States.DocumentLevelStateSelector.GetState(ProjectStatusItem projectStatusItem) in Mendix.Modeler.VersionControl.View\Status\States\DocumentLevelStateSelector.cs:line 48
   at Mendix.Modeler.VersionControl.Status.RevStatusControlEto.NavigateToSelectedItem(ProjectStatusGrid projectStatusGrid, ProjectStatusItem item) in Mendix.Modeler.VersionControl.View\Status\RevStatusControlEto.cs:line 446
   at Mendix.Modeler.VersionControl.Status.RevStatusControlEto.NavigateToProjectStatusGridSelection(ProjectStatusGrid projectStatusGrid) in Mendix.Modeler.VersionControl.View\Status\RevStatusControlEto.cs:line 436
   at Mendix.Modeler.VersionControl.Status.RevStatusControlEto.GoToSelectedItem() in Mendix.Modeler.VersionControl.View\Status\RevStatusControlEto.cs:line 416
   at Eto.Forms.RelayCommand.<>c__DisplayClass1_0.<.ctor>b__0(Object obj)
   at Eto.Forms.RelayCommand`1.Execute(Object parameter)
   at Mendix.Modeler.VersionControl.Status.RevStatusControlEto.ExecuteGoToCommand() in Mendix.Modeler.VersionControl.View\Status\RevStatusControlEto.cs:line 407
   at Mendix.Modeler.VersionControl.Status.RevStatusControlEto.ProjectStatusGridOnActivateRow(Object sender, Object item) in Mendix.Modeler.VersionControl.View\Status\RevStatusControlEto.cs:line 399
   at Mendix.Modeler.Controls.Grids.Grid`1.OnCellDoubleClick(Object sender, GridCellMouseEventArgs e) in Mendix.Modeler.Controls\Grids\GridOfT.cs:line 533
   at Eto.Forms.Grid.OnCellDoubleClick(GridCellMouseEventArgs e)
   at Eto.Forms.Grid.Callback.OnCellDoubleClick(Grid widget, GridCellMouseEventArgs e)
   at Mendix.Modeler.Controls.Windows.Grids.EtoGridHandler.OnControlMouseDoubleClicked(Object sender, MouseButtonEventArgs e) in Mendix.Modeler.Controls.Windows\Grids\EtoGridHandler.cs:line 315
   at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
   at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
   at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
   at System.Windows.Controls.Control.HandleDoubleClick(Object sender, MouseButtonEventArgs e)
   at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
   at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
   at System.Windows.UIElement.ReRaiseEventAs(DependencyObject sender, RoutedEventArgs args, RoutedEvent newEvent)
   at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
   at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
   at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
   at System.Windows.Input.InputManager.ProcessStagingArea()
   at System.Windows.Interop.HwndMouseInputProvider.ReportInput(IntPtr hwnd, InputMode mode, Int32 timestamp, RawMouseActions actions, Int32 x, Int32 y, Int32 wheel)
   at System.Windows.Interop.HwndMouseInputProvider.FilterMessage(IntPtr hwnd, WindowMessage msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   at System.Windows.Interop.HwndSource.InputFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
   at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
   at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)

Environment

• Mendix Studio Pro: 11.12.4
• mxcli: 0.23
• Operating system: Windows
• Entity type: non-persistent
• Operation: ALTER ENTITY ... MODIFY ATTRIBUTE
• Attribute change: String(255) to String(unlimited)

Additional Information

• The attribute change itself appears to be applied correctly.
• The Domain Model editor opens normally.
• The issue occurs specifically when opening the details of the change from the Changes panel.
• The exception appears related to a difference between the properties represented in the base and modified domain-model objects, but it is unclear whether the problem originates in mxcli-generated MPR metadata or in Studio Pro’s change-difference renderer.
• Avoiding the Changes-panel detail view allows continued work with the project.

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Issue Triage

Summary:
Studio Pro throws an exception when trying to view the details of a change made by ALTER ENTITY … MODIFY ATTRIBUTE after running the change with mxcli.

Checklist for bug report completeness

Required info	Present?	Details
mxcli version	✅	0.23 (listed in Environment)
Mendix version of project	✅	Project started on 10.x, currently on 11.12.4
Scenario (what was done)	✅	ALTER ENTITY … MODIFY ATTRIBUTE via mxcli, steps to reproduce
Expected output	✅	Studio Pro should show the attribute change details
Experienced output (error/crash)	✅	Exception with stack trace when opening the change details
AI bug report (mxcli diag --bundle or session log)	❌	Not provided

Missing information:
Could you please attach the output of mxcli diag --bundle (or at least the session log) so we can examine the exact MPR changes mxcli produced? This will help us pinpoint whether the issue lies in the generated metadata or in Studio Pro’s change‑difference rendering.

Thank you for the detailed report! Once we have the diagnostic bundle, we’ll be able to investigate further.

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