Check function for UninstallDelete is called upon installation

Question

I'm using Inno Setup to make my (un)installer. I want to make possibility to remove some "leftover" files after uninstall optionally, so I use [UninstallDelete] section with Check function for this. Function returns some value, but also shows some debug message. Something like this:

[UninstallDelete]
Type: filesandordirs; Name: "{app}\Plugins"; Check: ShouldRemovePlugins

[Code]
//...
var
  DelPlugins: Boolean;
//...
function ShouldRemovePlugins(): Boolean;
var text:string;
begin
  if(DelPlugins = true) then
    text := 'We should remove plugins'
  else
    text := 'We should not remove plugins';
  MsgBox(text, mbInformation, MB_OK);
  Result := DelPlugins;
end;

The thing is, that according to message box popping up, function is somehow called on install, not uninstall. So, question is - why so? Is it something about Inno Setup "workflow"?

Answer 1

It's determined during installation which uninstall tasks (including, but not limited to UninstallDelete entries) will be performed on uninstall.

So your Check function will indeed by called during installation.

---

See how processing UninstallDelete section is a step of installation:

Once the actual installation process begins, this is the order in which the various installation tasks are performed:

• [InstallDelete] is processed.
• The entries in [UninstallDelete] are stored in the uninstall log (which, at this stage, is stored in memory).
• The application directory is created, if necessary.
• ...

---

To delete files conditionally during uninstallation you have to code this explicitly in CurUninstallStepChanged event function.

Use usUninstall or usPostUninstall step.