MRTK Build Tool triggers indefinite "Importing" dialog in Unity 2020

[srinjoym]

Describe the bug

The MRTK Build Window triggers Unity 2020 to start an indefinite "Importing" message. I've reproduced on an empty Unity 2020 project with just MRTK 2.6.1:

To reproduce

Steps to reproduce the behavior:

1. Create a new Unity 2020 LTS Project
2. Add MRTK Foundation and Tools
3. Click "Build All" on the build window to start a build
4. After the build finishes, Unity 2020 starts showing an indefinite "Importing" message.

Expected behavior

This doesn't happen on Unity 2019 LTS - might be an issue with where the Build Assets are placed in Unity 2020?

Your setup (please complete the following information)

• Unity Version 2020.3.3
• MRTK Version v2.6.1

Target platform (please complete the following information)

• HoloLens 2

[CDiaz-MS]

I can repro this issue and we are continuing to investigate. It does occur in Unity 2020 and not Unity 2019.

[david-c-kline]

I'm working the @CDiaz-MS to see if we can isolate the portion of the MRTK Build Window that might be causing this. It is possible that there is a behavior change between Unity 2019 and 2020 that may require a coding change.

[david-c-kline]

While investigating this, @CDiaz-MS and I came upon the following line in the MRTK EditorAssemblyReloadManager

EditorApplication.delayCall += () => AssetDatabase.Refresh(ImportAssetOptions.ForceUpdate);

We tried removing this line and also removing the Refresh() parameter and we still encounter the loop.

[david-c-kline]

Testing was done on Unity 2020.3.8f1. This does not occur on previous versions (ex: 2019.4)

[david-c-kline]

The more we look at this, the mo.re if seems like a behavior change in Unity 2020

[david-c-kline]

Disabled the two likely causes of the importing trigger to no avail. From what I am seeing, I cannot identify where MRTK is doing something that is the root cause,

[david-c-kline]

Here are the changes that were attempted:

EditorAssemblyReloadManager.cs

#if !UNITY_2020_3_OR_NEWER
                    EditorApplication.delayCall += () => AssetDatabase.Refresh(ImportAssetOptions.ForceUpdate);
#endif

ProjectPreferences.cs

#if !UNITY_2020_3_OR_NEWER
                        AssetDatabase.Refresh();
#endif

[david-c-kline]

@keveleigh has narrowed this down further and found that without the appx build step, this does not repro.

Will investigate with him to see if we can identify the cause.

[david-c-kline]

Contacted Unity. They are able to repro this issue (and potentially in a similar scenario). Moving this to the 2.x future milestone.

[keveleigh]

Unity provided an update with why it's newly failing (they hardened some state logic requiring a ClearProgressBar call), so I opened #10046 to fix! I double checked the rest of our progress bar calls, and this was the only one missing a corresponding clear.