msbuild task: wait for file to exist

gistfile1.txt

    <WaitFor FilePath="$(MSBuildProjectDirectory)/../../samples/unity-of-bugs/Library/ScriptAssemblies/UnityEngine.TestRunner.dll" Delay="5000" />


  <UsingTask
    TaskName="WaitFor"
    TaskFactory="RoslynCodeTaskFactory"
    AssemblyFile="$(MSBuildToolsPath)\Microsoft.Build.Tasks.Core.dll" >
    <ParameterGroup>
      <FilePath ParameterType="System.String" Required="true" />
      <Delay ParameterType="System.Int32" Required="true" />
    </ParameterGroup>
    <Task>
      <Code Type="Fragment" Language="cs">
      <![CDATA[
int iterations = 10;
var sleep = this.Delay / iterations;

var i = 0;
do
{
    if (System.IO.File.Exists(this.FilePath))
    {
        return true;
    }
    Log.LogMessage($"Waiting ({i}x) {sleep}ms for {this.FilePath}.");
    System.Threading.Thread.Sleep(sleep);
} while (++i < iterations);
Log.LogError($"Waited but couldn't find {this.FilePath}.");
]]>
      </Code>
    </Task>
  </UsingTask>

/Applications/Unity/Hub/Editor/2019.4.21f1/Unity.app/Contents/MacOS/Unity -quit -batchmode -nographics -logFile - -projectPath samples/unity-of-bugs -buildMacOS64Player game

https://docs.microsoft.com/en-us/dotnet/api/system.threading.spinwait.spinuntil?view=net-5.0