solver3: Consider packages as obsolete and not versions

This makes more sense, as all package versions are obsolete that
are not the candidate, usually.

Pay special attention to no-strict-pinning: If we don't have
strict pinning, a package without a candidate version may still
be non-obsolete if the latest version is not obsolete.

Likewise, in no-strict-pinning any later source version that exists
will cause the package to be considered obsolete, rather than just
candidates.

2 files changed, 26 insertions, 13 deletions

diff --git a/apt-pkg/solver3.cc b/apt-pkg/solver3.cc
index 7580d6e18..29bd3a115 100644
--- a/apt-pkg/solver3.cc
+++ b/apt-pkg/solver3.cc
@@ -64,8 +64,8 @@ struct APT::Solver::CompareProviders3 /*{{{*/
       // Try obsolete choices only after exhausting non-obsolete choices such that we install
       // packages replacing them and don't keep back upgrades depending on the replacement to
       // keep the obsolete package installed.
-      if (auto obsoleteAV = Solver.Obsolete(AV), obsoleteBV = Solver.Obsolete(BV); obsoleteAV != obsoleteBV)
-	 return obsoleteBV;
+      if (auto obsoleteA = Solver.Obsolete(A), obsoleteB = Solver.Obsolete(B); obsoleteA != obsoleteB)
+	 return obsoleteB;
       // Prefer MA:same packages if other architectures for it are installed
       if ((AV->MultiArch & pkgCache::Version::Same) == pkgCache::Version::Same ||
 	  (BV->MultiArch & pkgCache::Version::Same) == pkgCache::Version::Same)
@@ -166,7 +166,7 @@ APT::Solver::Solver(pkgCache &cache, pkgDepCache::Policy &policy)
       policy(policy),
       pkgStates(cache.Head().PackageCount),
       verStates(cache.Head().VersionCount),
-      verObsolete(cache.Head().VersionCount)
+      pkgObsolete(cache.Head().PackageCount)
 {
    static_assert(sizeof(APT::Solver::State<pkgCache::PkgIterator>) == 3 * sizeof(int));
    static_assert(sizeof(APT::Solver::State<pkgCache::VerIterator>) == 3 * sizeof(int));
@@ -246,23 +246,36 @@ std::string APT::Solver::WhyStr(Reason reason)
    return outstr;
 }
 
-bool APT::Solver::Obsolete(pkgCache::VerIterator ver)
+bool APT::Solver::Obsolete(pkgCache::PkgIterator pkg)
 {
-   if (verObsolete[ver->ID] != 0)
-      return verObsolete[ver->ID] == 2;
+   auto ver = policy.GetCandidateVer(pkg);
+
+   if (ver.end() && not StrictPinning)
+      ver = pkg.VersionList();
+   if (ver.end())
+   {
+      std::cerr << "Obsolete: " << pkg.FullName() << " - not installable\n";
+      return true;
+   }
+   if (pkgObsolete[pkg->ID] != 0)
+      return pkgObsolete[pkg->ID] == 2;
    for (auto bin = ver.Cache()->FindGrp(ver.SourcePkgName()).VersionsInSource(); not bin.end(); bin = bin.NextInSource())
-      if (bin != ver && bin.ParentPkg()->Arch == ver.ParentPkg()->Arch && bin->ParentPkg != ver->ParentPkg && policy.GetCandidateVer(bin.ParentPkg()) == bin && _system->VS->CmpVersion(bin.SourceVerStr(), ver.SourceVerStr()) > 0)
+      if (bin != ver && bin.ParentPkg()->Arch == ver.ParentPkg()->Arch && bin->ParentPkg != ver->ParentPkg && (not StrictPinning || policy.GetCandidateVer(bin.ParentPkg()) == bin) && _system->VS->CmpVersion(bin.SourceVerStr(), ver.SourceVerStr()) > 0)
       {
-	 verObsolete[ver->ID] = 2;
+	 pkgObsolete[pkg->ID] = 2;
+	 if (debug >= 3)
+	    std::cerr << "Obsolete: " << ver.ParentPkg().FullName() << "=" << ver.VerStr() << " due to " << bin.ParentPkg().FullName() << "=" << bin.VerStr() << "\n";
 	 return true;
       }
    for (auto file = ver.FileList(); !file.end(); file++)
       if ((file.File()->Flags & pkgCache::Flag::NotSource) == 0)
       {
-	 verObsolete[ver->ID] = 1;
+	 pkgObsolete[pkg->ID] = 1;
 	 return false;
       }
-   verObsolete[ver->ID] = 2;
+   if (debug >= 3)
+      std::cerr << "Obsolete: " << ver.ParentPkg().FullName() << "=" << ver.VerStr() << " - not installable\n";
+   pkgObsolete[pkg->ID] = 2;
    return true;
 }
 
@@ -533,7 +546,7 @@ bool APT::Solver::EnqueueOrGroup(pkgCache::DepIterator start, pkgCache::DepItera
 		   { return pkgCache::VerIterator(cache, V).ParentPkg()->CurrentVer == 0; }))
       workItem.group = Group::SatisfyNew;
    if (std::any_of(workItem.solutions.begin(), workItem.solutions.end(), [this](auto V) -> auto
-		   { return Obsolete(pkgCache::VerIterator(cache, V)); }))
+		   { return Obsolete(pkgCache::VerIterator(cache, V).ParentPkg()); }))
       workItem.group = Group::SatisfyObsolete;
    // Try to perserve satisfied Recommends. FIXME: We should check if the Recommends was there in the installed version?
    if (workItem.optional && start.ParentPkg()->CurrentVer)
diff --git a/apt-pkg/solver3.h b/apt-pkg/solver3.h
index 9a9d67a02..d460c95d9 100644
--- a/apt-pkg/solver3.h
+++ b/apt-pkg/solver3.h
@@ -104,8 +104,8 @@ class Solver
       return verStates[V->ID];
    }
 
-   std::vector<char> verObsolete;
-   bool Obsolete(pkgCache::VerIterator ver);
+   std::vector<char> pkgObsolete;
+   bool Obsolete(pkgCache::PkgIterator pkg);
 
    // \brief Heap of the remaining work.
    //