solver3: Refactor Install(Ver) to PropagateInstall(Ver)

This is the first part of changing from Install() to Enqueue() for
installs, affecting only the versions. For packages, we still have
to resolve the group changing: When propagating cleanly, we don't
have the information as to which group the package was part of,
hence we are no longer able to queue the version selection of
upgrades before obsolete packages, for example, which needs
solving.

2 files changed, 36 insertions, 32 deletions

diff --git a/apt-pkg/solver3.cc b/apt-pkg/solver3.cc
index 7f382646a..4c1adef4b 100644
--- a/apt-pkg/solver3.cc
+++ b/apt-pkg/solver3.cc
@@ -322,6 +322,9 @@ bool APT::Solver::Enqueue(Var var, bool decision, Var reason)
       return true;
    }
 
+   if (auto Ver = var.Ver(cache); !Ver.end() && decision && unlikely(debug >= 1))
+      assert(IsAllowedVersion(Ver));
+
    state.decision = decisionCast;
    state.depth = depth();
    state.reason = reason;
@@ -337,7 +340,11 @@ bool APT::Solver::Enqueue(Var var, bool decision, Var reason)
 	 return false;
       needsRescore = true;
    }
-
+   else
+   {
+      if (not PropagateInstall(var))
+	 return false;
+   }
    return true;
 }
 
@@ -377,7 +384,7 @@ bool APT::Solver::Install(pkgCache::PkgIterator Pkg, Var reason, Group group)
 
    if (workItem.solutions.size() > 1 || workItem.optional)
       AddWork(std::move(workItem));
-   else if (not Install(pkgCache::VerIterator(cache, workItem.solutions[0]), workItem.reason, group))
+   else if (not Enqueue(Var(pkgCache::VerIterator(cache, workItem.solutions[0])), true, workItem.reason))
       return false;
 
    if (not EnqueueCommonDependencies(Pkg))
@@ -386,35 +393,32 @@ bool APT::Solver::Install(pkgCache::PkgIterator Pkg, Var reason, Group group)
    return true;
 }
 
-bool APT::Solver::Install(pkgCache::VerIterator Ver, Var reason, Group group)
+bool APT::Solver::PropagateInstall(Var var)
 {
-   if ((*this)[Ver].decision == Decision::MUST)
-      return true;
-
-   if (unlikely(debug >= 1))
-      assert(IsAllowedVersion(Ver));
-
-   // Note decision
-   if (not Enqueue(Var(Ver), true, reason))
-      return false;
-   if (not Enqueue(Var(Ver.ParentPkg()), true, Var(Ver)))
-      return false;
-
-   for (auto OV = Ver.ParentPkg().VersionList(); not OV.end(); ++OV)
+   if (auto Pkg = var.Pkg(cache); not Pkg.end())
    {
-      if (OV != Ver && not Enqueue(Var(OV), false, Var(Ver)))
-	 return false;
    }
-
-   for (auto dep = Ver.DependsList(); not dep.end();)
+   else if (auto Ver = var.Ver(cache); not Ver.end())
    {
-      // Compute a single dependency element (glob or)
-      pkgCache::DepIterator start;
-      pkgCache::DepIterator end;
-      dep.GlobOr(start, end); // advances dep
-
-      if (not EnqueueOrGroup(start, end, Var(Ver)))
+      if (not Enqueue(Var(Ver.ParentPkg()), true, Var(Ver)))
 	 return false;
+
+      for (auto OV = Ver.ParentPkg().VersionList(); not OV.end(); ++OV)
+      {
+	 if (OV != Ver && not Enqueue(Var(OV), false, Var(Ver)))
+	    return false;
+      }
+
+      for (auto dep = Ver.DependsList(); not dep.end();)
+      {
+	 // Compute a single dependency element (glob or)
+	 pkgCache::DepIterator start;
+	 pkgCache::DepIterator end;
+	 dep.GlobOr(start, end); // advances dep
+
+	 if (not EnqueueOrGroup(start, end, Var(Ver)))
+	    return false;
+      }
    }
 
    return true;
@@ -608,7 +612,7 @@ bool APT::Solver::EnqueueOrGroup(pkgCache::DepIterator start, pkgCache::DepItera
       }
       if (workItem.optional || workItem.solutions.size() > 1)
 	 AddWork(std::move(workItem));
-      else if (not Install(pkgCache::VerIterator(cache, workItem.solutions[0]), reason, workItem.group))
+      else if (not Enqueue(Var(pkgCache::VerIterator(cache, workItem.solutions[0])), true, reason))
 	 return false;
    }
    else if (start.IsCritical() && not start.IsNegative())
@@ -901,7 +905,7 @@ bool APT::Solver::Solve()
 	 }
 	 if (unlikely(debug >= 3))
 	    std::cerr << "(try it: " << ver.ParentPkg().FullName() << "=" << ver.VerStr() << ")\n";
-	 if (not Install(pkgCache::VerIterator(cache, ver), item.reason, Group::Satisfy) && not Pop())
+	 if (not Enqueue(Var(pkgCache::VerIterator(cache, ver)), true, item.reason) && not Pop())
 	    return false;
 	 foundSolution = true;
 	 break;
@@ -942,7 +946,7 @@ bool APT::Solver::FromDepCache(pkgDepCache &depcache)
       {
 	 if (unlikely(debug >= 1))
 	    std::cerr << "Hold " << P.FullName() << "\n";
-	 if (P->CurrentVer ? not Install(P.CurrentVer(), {}, Group::HoldOrDelete) : not Enqueue(Var(P), false, Var()))
+	 if (P->CurrentVer ? not Enqueue(Var(P.CurrentVer()), true, {}) : not Enqueue(Var(P), false, Var()))
 	    return false;
       }
       else if (state.Delete()						  // Normal delete request.
@@ -979,7 +983,7 @@ bool APT::Solver::FromDepCache(pkgDepCache &depcache)
 	 if (not isOptional)
 	 {
 	    // Pre-empt the non-optional requests, as we don't want to queue them, we can just "unit propagate" here.
-	    if (depcache[P].Keep() ? not Install(P, {}, Group) : not Install(depcache.GetCandidateVersion(P), {}, Group))
+	    if (depcache[P].Keep() ? not Install(P, {}, Group) : not Enqueue(Var(depcache.GetCandidateVersion(P)), true, {}))
 	       return false;
 	 }
 	 else
diff --git a/apt-pkg/solver3.h b/apt-pkg/solver3.h
index de1bd1e73..0e6d0e2f9 100644
--- a/apt-pkg/solver3.h
+++ b/apt-pkg/solver3.h
@@ -153,6 +153,8 @@ class Solver
    bool RejectReverseDependencies(pkgCache::VerIterator Ver);
    // \brief Enqueue a single or group
    bool EnqueueOrGroup(pkgCache::DepIterator start, pkgCache::DepIterator end, Var reason);
+   // \brief Propagate a "true" value of a variable
+   bool PropagateInstall(Var var);
    // \brief Propagate a rejection of a variable
    bool PropagateReject(Var var);
    // \brief Check if a version is allowed by policy.
@@ -186,8 +188,6 @@ class Solver
 
    // \brief Mark the package for install. This is annoying as it incurs a decision
    bool Install(pkgCache::PkgIterator Pkg, Var reason, Group group);
-   // \brief Install a version.
-   bool Install(pkgCache::VerIterator Ver, Var reason, Group group);
 
    // \brief Apply the selections from the dep cache to the solver
    bool FromDepCache(pkgDepCache &depcache);