Unit test intermittently fails

[Tanya-Solyanik]

DesignerHost_Add_ComponentDisposeThrowsDuringUnloadingDispose_ThrowsInvalidOperationException might have a race condition

https://github.com/dotnet/winforms/blob/774bd34a750016e596808bc6106d63b79dff2462/src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/DesignerHostTests.cs#L1801-#1814

[hughbe]

Hmmm - i'm a bit surprised because there shouldn't be any async stuff interfering with this

[hughbe]

Possibly related: a failure in DesignSurface_View_GetWithInvalidSupportedTechnologies_ThrowsNotSupportedException in # 1508

Error message
Assert.Throws() Failure\r\nExpected: typeof(System.NotSupportedException)\r\nActual: typeof(System.InvalidOperationException): The CurrentContext property of the LicenseManager is currently locked and cannot be changed.\r\n---- System.InvalidOperationException : The CurrentContext property of the LicenseManager is currently locked and cannot be changed.\r\n-------- System.InvalidOperationException : The CurrentContext property of the LicenseManager is currently locked and cannot be changed.

Stack trace
at System.ComponentModel.Design.DesignSurface.get_View() in F:\workspace_work\1\s\src\System.Windows.Forms.Design\src\System\ComponentModel\Design\DesignSurface.cs:line 161
at System.ComponentModel.Design.Tests.DesignSurfaceTests.<>c__DisplayClass23_0.<DesignSurface_View_GetWithInvalidSupportedTechnologies_ThrowsNotSupportedException>b__0() in F:\workspace_work\1\s\src\System.Windows.Forms.Design\tests\UnitTests\System\ComponentModel\Design\DesignSurfaceTests.cs:line 340
----- Inner Stack Trace -----
at System.ComponentModel.Design.DesignSurface.get_View() in F:\workspace_work\1\s\src\System.Windows.Forms.Design\src\System\ComponentModel\Design\DesignSurface.cs:line 161
at System.ComponentModel.Design.Tests.DesignSurfaceTests.<>c__DisplayClass23_0.<DesignSurface_View_GetWithInvalidSupportedTechnologies_ThrowsNotSupportedException>b__0() in F:\workspace_work\1\s\src\System.Windows.Forms.Design\tests\UnitTests\System\ComponentModel\Design\DesignSurfaceTests.cs:line 340
----- Inner Stack Trace -----
at System.ComponentModel.LicenseManager.set_CurrentContext(LicenseContext value)
at System.ComponentModel.Design.DesignerHost.System.ComponentModel.Design.IDesignerHost.CreateComponent(Type componentType, String name) in F:\workspace_work\1\s\src\System.Windows.Forms.Design\src\System\ComponentModel\Design\DesignerHost.cs:line 1034
at System.ComponentModel.Design.DesignerHost.System.ComponentModel.Design.IDesignerHost.CreateComponent(Type componentType) in F:\workspace_work\1\s\src\System.Windows.Forms.Design\src\System\ComponentModel\Design\DesignerHost.cs:line 1016
at System.ComponentModel.Design.DesignSurface.DefaultDesignerLoader.BeginLoad(IDesignerLoaderHost loaderHost) in F:\workspace_work\1\s\src\System.Windows.Forms.Design\src\System\ComponentModel\Design\DesignSurface.cs:line 592
at System.ComponentModel.Design.DesignerHost.BeginLoad(DesignerLoader loader) in F:\workspace_work\1\s\src\System.Windows.Forms.Design\src\System\ComponentModel\Design\DesignerHost.cs:line 328

[hughbe]

Another possibly related failure in #1527

System.ComponentModel.Design.Tests.DesignerHostTests.DesignerHost_Add_DuringUnload_ThrowsException [FAIL]

  System.Exception : There is no designer for the class System.ComponentModel.Design.Tests.DesignerHostTests+DesignerComponent.
  Stack Trace:
    /_/src/System.Windows.Forms.Design/src/System/ComponentModel/Design/DesignerHost.cs(244,0): at System.ComponentModel.Design.DesignerHost.AddToContainerPostProcess(IComponent component, String name, IContainer containerToAddTo)
    /_/src/System.Windows.Forms.Design/src/System/ComponentModel/Design/DesignerHost.cs(151,0): at System.ComponentModel.Design.DesignerHost.PerformAdd(IComponent component, String name)
    /_/src/System.Windows.Forms.Design/src/System/ComponentModel/Design/DesignerHost.cs(141,0): at System.ComponentModel.Design.DesignerHost.Add(IComponent component, String name)
       at System.ComponentModel.Container.Add(IComponent component)
    /_/src/System.Windows.Forms.Design/tests/UnitTests/System/ComponentModel/Design/DesignerHostTests.cs(874,0): at System.ComponentModel.Design.Tests.DesignerHostTests.DesignerHost_Add_DuringUnload_ThrowsException()

Looking at the stack trace, we must be returning from DesignSurface.CreateDesigner.

protected internal virtual IDesigner CreateDesigner(IComponent component, bool rootDesigner)
{
    if (component == null)
    {
        throw new ArgumentNullException(nameof(component));
    }

    if (_host == null)
    {
        throw new ObjectDisposedException(GetType().FullName);
    }

    IDesigner designer;
    if (rootDesigner)
    {
        designer = TypeDescriptor.CreateDesigner(component, typeof(IRootDesigner)) as IRootDesigner;
    }
    else
    {
        designer = TypeDescriptor.CreateDesigner(component, typeof(IDesigner));
    }
    return designer;
}

but i'm not sure how TypeDescriptor.CreateDesigner could return null!