An "XmlSchemaException" error is thrown when updating UXML schema with App UI package installed

Package: App UI

This issue has been closed as a duplicate of:

Error "UXML validation error: Line 3, Position 6: The element 'VisualElement' in namespace 'UnityEngine.UIElements' has incomplete content." is present when running the test for Schema Definitions

Duplicate

2.2.X

How to reproduce:
1. Create and open a new project
2. Open package manager (Window > Package management > Package Manager)
3. Install App UI package (com.unity.dt.app-ui)
4. In the app menu, navigate to Assets > Update UXML Schema
5. Observe the Console

Actual result: An “XmlSchemaException: The simpleType 'Unity.AppUI.UI:VariantType' has already been declared.” error is thrown
Expected result: No errors are thrown

Reproducible with: 1.2.0 (6000.4.0a1), 2.2.0-pre.3 (6000.4.0a1, 6000.4.0b1, 6000.5.0a3)
Not reproducible with: 2.2.0-pre.3 (6000.0.64f1, 6000.3.0a6)

Reproducible on: macOS 26.1 (M1 Pro)
Not reproducible on: No other environments tested

An "XmlSchemaException" error is thrown when updating UXML schema with App UI package installed

Package: App UI

Duplicate

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Have a workaround or additional info about this issue?

An "XmlSchemaException" error is thrown when updating UXML schema with App UI package installed

Package: App UI

Statuses

Duplicate

Resolution Notes

Description

Prioritise and Follow this issue

Have a workaround or additional info about this issue?