[RF] Writing copy of RooWorkspace messes up proxies

[guitargeek]

Take this workspace here:
workspace.root.txt

Now run this reproducer code:

void repro() {

   {
      std::unique_ptr<TFile> f{TFile::Open("workspace.root")};
      RooWorkspace* combined = f->Get<RooWorkspace>("combined"); // load the original
      cout << combined->function("gaus_x1y1_OSeMmuP_fakeOverall")->getProxy(0) << std::endl; // this is non-zero
      combined->writeToFile("another.root"); // supposed to create a nice copy
   }

   std::unique_ptr<TFile> f{TFile::Open("another.root")};
   RooWorkspace* w = f->Get<RooWorkspace>("combined"); // load the copy
   cout << w->function("gaus_x1y1_OSeMmuP_fakeOverall")->getProxy(0) << std::endl; // this is zero ???
}

The output will be:

0x55925a4e95c0
0

That's not good. When copying a workspace, the proxies should not be set to zero!

Note that the .txt suffix has to be removed from the input file. It's just there to be able to upload the workspace to GitHub.

Thanks to @will-cern for reporting this.