Question Unity upgrade breaks UXMLs

Hi, I have multiple UXMLs created a while back, plus some created in 2021.2.4f1 (where everything works).

After upgrading editor to 2022.1.0a16, the asset import fails on many of them. Does not seem to matter which previous version they were created in.

ArgumentNullException: Value cannot be null.
Parameter name: key

Some UXMLs lose their icon and association with UI Builder (they open in IDE). Others retain the link but the builder fails to open them: UI Builder - Unable to parse UXML file.

Spoiler: Console details

UI Builder Failed to open Assets/Content/UIDocuments/ModPanelContainer.uxml.uxml asset. This may be due to invalid UXML syntax or UXML syntax the UI Builder does not yet support. Check console for details.
UnityEngine.Debug:LogError (object)
Unity.UI.Builder.BuilderAssetUtilities:ValidateAsset (UnityEngine.UIElements.VisualTreeAsset,string) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui.builder/Editor/Builder/Utilities/BuilderAssetUtilities.cs:77)
Unity.UI.Builder.BuilderToolbar:LoadDocument (UnityEngine.UIElements.VisualTreeAsset,bool,bool,string) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui.builder/Editor/Builder/Toolbar/BuilderToolbar.cs:385)
Unity.UI.Builder.Builder:LoadDocument (UnityEngine.UIElements.VisualTreeAsset,bool) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui.builder/Editor/Builder/Builder.cs:210)
Unity.UI.Builder.Builder:OnOpenAsset (int,int) (at /Users/bokken/buildslave/unity/build/External/MirroredPackageSources/com.unity.ui.builder/Editor/Builder/Builder.cs:287)
UnityEngine.GUIUtilityrocessEvent (int,intptr,bool&) (at /Users/bokken/buildslave/unity/build/Modules/IMGUI/GUIUtility.cs:189)

Note on the double ".uxml" extension in console reference: The file on drive is just single .uxml

Thank you for any ideas!

 

Thanks, that's great news!

 

Running 2022.2.8f1 and it still seems to be an issue. The solution for me was to remove

<Style>

references to missing assets.