Delphi EInOutError exception is not raised - delphi

Question

I am trying to copy directory:
procedure CopyBigDirWithSubdirs;
{$IOCHECKS ON}
begin
try
TDirectory.Copy(SrcPath, DstPath);
except
on E: EInOutError do something
end;
end;
In my case it is crucial to check disk full condition and I hoped that catching EInOutError exception would solve my problem. But as far as I could find out TDirectory methods do not notify of this condition at all. The situation is even worse because TDirectory.copy can write part of subdirs, face disk full condition and terminate, so I have to check the whole directory tree to be sure that my directory is copied properly. Does anybody know better solution?

Answer 1

{$IOCHECKS ON} isn't relevant here. That's for legacy Pascal I/O. And likewise for EInOutError, you aren't ever going to get that from functions in the IOUtils unit.
The real problem here is that TDirectory.Copy is, like so much of IOUtils, broken by design. There appears to be no error checking whatsoever implemented in TDirectory.Copy. For what it is worth, the rule at my place of work is that IOUtils must not be used in our code.
You are going to have to either write your own code which does include some error checking, or find a third party library to do the work.
Certainly on Windows then you should use IFileOperation to do this. As a benefit you'll even be able to show the standard system progress dialog. And because the code is provided by the system rather than by Embarcadero, you can expect it to work.
If you require support for other platforms then you may have to work a little harder to find suitable code.

Answer 2

As using IFileOperation interface looks like most practical solution I've written the function based on it:
function CopyItem(const Src, Dest: string ): HRESULT;
const
FOF_SILENT = $0004;
FOF_NOCONFIRMATION = $0010;
FOF_NOCONFIRMMKDIR = $0200;
FOF_NOERRORUI = $0400;
FOF_NO_UI =(FOF_SILENT or FOF_NOCONFIRMATION or FOF_NOERRORUI or FOF_NOCONFIRMMKDIR); // don't display any UI at all
var
lFileOperation: IFileOperation;
psiFrom: IShellItem;
psiTo: IShellItem;
opAborted : longbool;
begin
//We probably don't need to call CoInitializeEx/CoUninitialize pair as it could have been called by Delphi library
CoInitializeEx(nil, COINIT_APARTMENTTHREADED or COINIT_DISABLE_OLE1DDE);
// check arguments and create the IFileOperation interface,
if (Src='') or (Dest='') then Result := E_INVALIDARG
else Result := CoCreateInstance(CLSID_FileOperation, nil, CLSCTX_ALL, IFileOperation, lFileOperation);
// Set the operation flags. Turn off all UI from being shown to the user
if Succeeded(Result) then Result := lFileOperation.SetOperationFlags(FOF_NO_UI);
// Create IShellItem-s from the supplied source and dest paths.
if Succeeded(Result) then Result := SHCreateItemFromParsingName(PWideChar(wideString(Src)),
nil, IShellItem, psiFrom);
if Succeeded(Result) then Result := SHCreateItemFromParsingName(PWideChar(wideString(Dest)),
nil, IShellItem, psiTo);
// This method does not copy the item, it merely declares the item to be copied
if Succeeded(Result) then Result := lFileOperation.CopyItem(psiFrom, psiTo, nil, nil);
// This method is called last to execute those actions that have been specified earlier
if Succeeded(Result) then Result := lFileOperation.PerformOperations;
// Check now if the operation was aborted by the system
if Succeeded(Result) then
begin
lFileOperation.GetAnyOperationsAborted(opAborted);
if opAborted then Result := ERROR_WRITE_FAULT;
end;
CoUninitialize;
end;
As you can see from the code the solution is not complete because in case of disc full error (my reason for all this fiddling with lFileOperation) PerformOperations returns S_OK (!!!) and I can find the error only by calling GetAnyOperationsAborted which does not specify the error condition exactly but merely sets opAborted flag. Then I have to guess the real case of abortion.