Start-UnityEditor fails if there are compiler errors even when passing -ErrorAction 'SilentlyContinue'

[mister-liss]

With previous versions of Unity, passing 'SilentlyContinue' to -ErrorAction would cause Unity to ignore initial compiler errors. This is impotant in cases where the Unity is expected to run code which will retrieve compile time dependencies. In Unity 2020, 'SilentlyContinue' doesn't seem to affect Unity and Start-UnityEditor will fail.

I experienced this issue using Nuget4Unity, which is a plugin that performs a nuget package restore after Unity starts. Since Unity fails to start now, the packages are never restored and Start-UnityEditor cannot be used.

Repro Steps:
-Create an empty Unity 2020 project (I am using Unity 2020.3.20f1)
-Import the Nuget4Unity plugin
-Add a Nuget package
-Create a script which references a .net type from the Nuget package
-run "sue [YourProjectPath] -AcceptAPIUpdate -BatchMode -Quit -Wait -BuildTarget 'WSAPlayer' -ErrorAction SilentlyContinue

Expected Result:
UnitySetup emits some errors about references to the types found in the Nuget package and continues to build the project.

Actual Result:
UnitySetup emits some errors about references to the types found in the Nuget package and then exits.

I reproduced this bug in both the release version 5.4.140 and the pre-release version 5.5.146-develop.

[mister-liss]

A user can circumvent this issue by using the -AdditionalArguements paramter with "-ignoreCompilerErrors" at the bottom of this page.

https://docs.unity3d.com/2020.2/Documentation/Manual/SafeMode.html

[jwittner]

Very strange - SilentlyContinue is a PowerShell construct and not a UnitySetup feature. As long as we're using Write-Error for the errors then PowerShell should continue running and not log the errors.

The exit from Unity is a Unity thing and not UnitySetup either - seems like first class support for 'IgnoreCompilerErrors' seems like the right fix there (we should make it a first class switch to sue).