Omnithread: Create a task wrapper / modify a task that adds some extra pre- and post processing to an alredy existing task

Some background:

Basically it comes down to that I want to be able to "execute" the task in the current thread. Why? -I have a task creator routine, and one time I want the task to be executed immediately in a background task, and at other times I want the task to be scheduled using an IOmniThreadPool.

In the case that I want to use the OmniThreadpool I want do do some output about the task's status, like that it was queued, started, finished or failed.

The task's execution is not yet started at this moment.

So I imagined someting like this:

function WrapIntoPoolTask(const aOriginalTask:IOmniTaskCOntrol):IOmniTaskCOntrol;
begin
  if Assigned(aOriginalTask) then
  begin
    var lPoolProgress:=TaskPoolProgress; // fetch global task pool progress interface
    // immediately displays message says its been queued, remember message bookmark
    var lMessageBookMark:=lPoolProgress.MessageList.AddMessage(aOriginalTask.Name,pmPaused);
    Result:=CreateTask(
      procedure (const aTask:IOmniTask)
      begin
        lPoolProgress.MessageList.UpdateMessage(lMessageBookMark,pmStarted); // update message status
        try

          aOriginalTask.ExecuteTaskInThisThread; // <<=== So how do I do this?

          lPoolProgress.MessageList.UpdateMessage(lMessageBookMark,pmCompleted);
        except
          lPoolProgress.MessageList.UpdateMessage(lMessageBookMark,pmFailed);
          raise;
        end;
      end
      ,
      'Pooled:'+aOriginalTask.Name
    );
  end;
end;

Using the UpdateMessage call after performing the original task can be moved to the OnTerminated handler of the IOmniTaskControl interface. I tried that and it works just fine for the thread ending part. It even allows for handling exit codes and exit messages which I like even better.

I think what I am missing here is probably an OnInitialize or OnStartExecution handler to set my pmStarted status.

Question:

• How can I directly execute a tasks "body" from IOmniTaskCOntrol

or

• how can I add some initialization code to my task after the task was already created. This code should be executed immediatliy prior to executing my tasks original body.

In order to solve my problem I had to change the omnithreadlibrary unit OtlTaskControl a bit.

one routine added to IOmniTaskControl (GUID should change, but I didn'tt)

  IOmniTaskControl = interface ['{881E94CB-8C36-4CE7-9B31-C24FD8A07555}']
...
    function DirectExecute:IOmniTaskControl;
...
  end; { IOmniTaskControl }

And the implementation added to TOmniTaskControl:

function TOmniTaskControl.DirectExecute:IOmniTaskControl;
VAR lTask:IOmniTask;
begin
  Result:=self;
  lTask:=CreateTask;
  (lTask as IOmniTaskExecutor).Execute;
end;

Then my "custom wrapper" routine that actually adds the pool progress handling to whatever the original task was:

function WrapIntoOmniPoolTask(const aTaskControl:IOmniTaskCOntrol):IOmniTaskCOntrol;
var lTaskControl:IOmniTaskCOntrol;
    lPoolProgress:IAppProgress;
    lmbm:integer;
begin
  if Assigned(aTaskControl) then
  begin
    // have some local copies to work around compiler bug RX10.3 and RX10.4
    // cannot use inline vars due to this bug either.
    lTaskControl:=aTaskControl;
    lPoolProgress:=TaskPoolProgress;
    lmbm:=lPoolProgress.MessageList.AddMessage(aTaskControl.Name,pmPaused);
    Result:=CreateTask(
      procedure (const aTask:IOmniTask)
      begin
        try
          lPoolProgress.MessageList.UpdateMessage(lmbm,pmStarted);
          try
            lTaskControl.DirectExecute;
            aTask.SetExitStatus(lTaskControl.ExitCode,lTaskControl.ExitMessage);
            HandlePoolTaskTermination(lTaskControl,lmbm,lPoolProgress);
          except
            HandlePoolTaskTermination(lTaskControl,lmbm,lPoolProgress);
            if IsFatalException then
              raise;
          end;
        finally
          // release interfaces when all is done
          lPoolProgress:=nil; 
          lTaskControl:=nil;
        end;
      end,
      'Pooled: '+lTaskCOntrol.Name
    );
  end;
end;

And finally, the routine that schedules my wrapped task into the omnipoolthread.

function TfrmMain.CreateTestTask:IOmniTaskControl;
begin
  Result:=WrapIntoOmniPoolTask(CreateTask(TestTask,TGUID.NewGuid.ToString)).Unobserved;
end;

Everything seems to work as expected including the exit code and exit message which are propagated from the inner task to the outer task.

The compiler bug I am referring to is reported here: https://quality.embarcadero.com/browse/RSP-29564 (please vote!)

---

For those interested: this is what HandlePoolTaskTermination looks like:

procedure HandlePoolTaskTermination(const aTaskControl:IOmniTaskCOntrol;const aMessageBookmark:integer;const aPoolProgress:IAppProgress);
begin
  var pm:=pmCompleted;
  if Assigned(aTaskControl.FatalException) then
  begin
    pm:=pmWarning;
    var pe:=peError;
    if IsAbortException(aTaskControl.FatalException) then
      pe:=peWarning
    else if IsFatalException(aTaskControl.FatalException) then
    begin
      pm:=pmFailed;
      pe:=peFatalError;
    end;
    aPoolProgress.ErrorList.AddErrorToMessage(aMessageBookmark,'',pe,aTaskControl.FatalException)
  end
  else if aTaskControl.ExitCode<>0 then
  begin
    pm:=pmWarning;
    aPoolProgress.ErrorList.AddErrorToMessage(aMessageBookmark,aTaskControl.ExitMessage,peWarning);
  end;
  aPoolProgress.MessageList.UpdateMessage(aMessageBookmark,pm);
end;

The IsFatalException returns true if the "current" exception is eg EAccessViolation, EInvalidOperation and alike.