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Fixed in 2021.2.X

Fixed in 2020.3.X, 2021.1.X



Found in



Issue ID




UnityException and ArgumentException errors are thrown when UI Toolkit is added to a new project



How to reproduce:
1. Create a new project
2. Open the created project's folder
3. Open the Packages folder
4. Open the manifest.json file with a text editor
5. Add this line to the manifest.json file: "com.unity.ui": "1.0.0-preview.6",
6. Go back to the Editor
7. Observe the Console log

Expected result: No errors are thrown in the Console log
Actual result: "UnityException: The MakeClientFunc has already been registered. Registration denied." and "ArgumentException: An item with the same key has already been added." error messages are thrown in the Console log (Full error messages in the edit)

Reproducible with: 2020.2.0a18, 2020.2.0a20 (1.0.0-preview.6)
Not reproducible with: 2020.1.2f1, 2020.2.0a17 (1.0.0-preview.6)
Could not test with: 2018.4.26f1, 2019.4.8f1 (UI Toolkit not supported)

- The Package Manager won't open after adding the package in the manifest.json file and restarting the Editor, the following error message appears in the Console log: "NullReferenceException: Object reference not set to an instance of an object" (Full error message in the edit)

  1. Resolution Note (fix version 2021.2):

    Fixed in: 2021.2.0a9

  2. Resolution Note (fix version 2021.1):

    Fixed in: 2021.1.12f1

  3. Resolution Note (fix version 2020.3):

    Fixed in: 2020.3.4f1

Comments (2)

  1. twaananen

    Apr 04, 2021 13:09

    Wait am I understanding this right, you have a fix for this now, when one latest version out is 2021.1.1f and you've scheduled it to roll out in some Fixed in: 2021.1.12f1, so maybe 6-12 months from now? Like this is preventing us from building working builds, shouldn't you escalate this?

  2. adam_unity302

    Mar 22, 2021 01:30

    Also issue with 2020.3.0f1

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