[RF] Register function as value server in pass-through RooRealIntegrals

In pass through mode, the RooRealIntegral should have registered the
function as a value server, because we directly depend on its value.

As it is only determined later in the constructor if a given integral is
in pass through mode, we also have to delay the construction of the
function proxy object now.

It's important to do this correctly, because the new BatchMode uses the
value server interface to analyze the computation graph.

Author: guitargeek

roofit/roofitcore/inc/RooArgProxy.h

@@ -61,6 +61,8 @@ class RooArgProxy : public TNamed, public RooAbsProxy  {
 
 protected:
 
+  friend class RooRealIntegral;
+
   bool changePointer(const RooAbsCollection& newServerSet, bool nameChange=false, bool factoryInitMode=false) override ;
 
   virtual void changeDataSet(const RooArgSet* newNormSet) ;

roofit/roofitcore/src/RooRealIntegral.cxx

@@ -102,8 +102,7 @@ RooRealIntegral::RooRealIntegral(const char *name, const char *title,
   _anaList("!anaList","Variables to be integrated analytically",this,false,false),
   _jacList("!jacList","Jacobian product term",this,false,false),
   _facList("!facList","Variables independent of function",this,false,true),
-  _function("!func","Function to be integrated",this,
-       const_cast<RooAbsReal&>(function),false,false),
+  _function("!func","Function to be integrated",this,false,false),
   _iconfig((RooNumIntConfig*)config),
   _sumCat("!sumCat","SuperCategory for summation",this,false,false),
   _mode(0),
@@ -406,7 +405,7 @@ RooRealIntegral::RooRealIntegral(const char *name, const char *title,
   RooArgSet anIntDepList ;
 
   RooArgSet *anaSet = new RooArgSet( _anaList, Form("UniqueCloneOf_%s",_anaList.GetName()));
-  _mode = ((RooAbsReal&)_function.arg()).getAnalyticalIntegralWN(anIntOKDepList,*anaSet,_funcNormSet,RooNameReg::str(_rangeName)) ;
+  _mode = function.getAnalyticalIntegralWN(anIntOKDepList,*anaSet,_funcNormSet,RooNameReg::str(_rangeName)) ;
   _anaList.removeAll() ;
   _anaList.add(*anaSet);
   delete anaSet;
@@ -539,9 +538,13 @@ RooRealIntegral::RooRealIntegral(const char *name, const char *title,
     // Purely analytical integration
     _intOperMode = Analytic ;
   } else {
-    // No integration performed
+    // No integration performed, where the function is a direct value server
     _intOperMode = PassThrough ;
+    _function._valueServer = true;
   }
+  // We are only setting the function proxy now that it's clear if it's a value
+  // server or not.
+  _function.setArg(const_cast<RooAbsReal&>(function));
 
   // Determine auto-dirty status
   autoSelectDirtyMode() ;
@@ -884,6 +887,10 @@ double RooRealIntegral::evaluate() const
 
   case PassThrough:
     {
+      // In pass through mode, the RooRealIntegral should have registered the
+      // function as a value server, because we directly depend on its value.
+      assert(_function.isValueServer());
+
       //setDirtyInhibit(true) ;
       retVal= _function.arg().getVal(_funcNormSet) ;
       //setDirtyInhibit(false) ;