Backup external file before Inno Setup InstallDelete section - backup

Question

I would make a backup of files and folders before the [InstallDelete] section deletes them
[Files]
Source: "{app}\res_mods\configs\wotstat\cache.json"; \
DestDir: "{app}\_backup\res_mods_{#DateTime}\configs\wotstat\"; \
Flags: external skipifsourcedoesntexist uninsneveruninstall
Source: "{app}\res_mods\0.9.17.1\vehicles\*"; \
DestDir:"{app}\_backup\res_mods_{#DateTime}\0.9.17.1\vehicles\"; \
Flags: external skipifsourcedoesntexist createallsubdirs recursesubdirs uninsneveruninstall
This works fine. But, if i check
[InstallDelete]
Type: filesandordirs; Name: "{app}\mods\*.*"; Tasks: cleanres
Type: filesandordirs; Name: "{app}\res_mods\*.*"; Tasks: cleanres
No files are saved
How I can made it work. Thx

Answer 1

The [InstallDelete] section is processed (as one would expect) before the [Files] section. See the installation order.
You can code the backup in the CurStepChanged(ssInstall) event, that happens before the installation starts:
[Code]
procedure CurStepChanged(CurStep: TSetupStep);
var
SourcePath: string;
DestPath: string;
begin
if CurStep = ssInstall then
begin
SourcePath := ExpandConstant('{app}\res_mods\0.9.17.1\vehicles');
DestPath :=
ExpandConstant('{app}\_backup\res_mods_{#DateTime}\0.9.17.1\vehicles');
Log(Format('Backing up %s to %s before installation', [
SourcePath, DestPath]));
if not ForceDirectories(DestPath) then
begin
Log(Format('Failed to create %s', [DestPath]));
end
else
begin
DirectoryCopy(SourcePath, DestPath);
end;
SourcePath := ExpandConstant('{app}\res_mods\configs\wotstat\cache.json');
DestPath :=
ExpandConstant('{app}\_backup\res_mods_{#DateTime}\configs\wotstat');
if not ForceDirectories(DestPath) then
begin
Log(Format('Failed to create %s', [DestPath]));
end
else
begin
if not FileCopy(SourcePath, DestPath + '\cache.json', False) then
begin
Log(Format('Failed to copy %s', [SourcePath]));
end
else
begin
Log(Format('Backed up %s', [SourcePath]));
end;
end;
end;
end;
The code uses the DirectoryCopy function from the Inno Setup: copy folder, subfolders and files recursively in Code section.