simulate all package manager actions explicitly

If a planner lets actions to be figured out by dpkg in pending calls
these actions aren't mentioned in a simulation. While that might be
a good thing for debugging, it would be a change in behavior and
especially if a planner avoids explicit removals could be confusing for
users. As such we perform the same 'trick' as in the dpkg implementation
by performing explicitly what would be done by the pending calls.

To save us some work and avoid desyncs we perform a layer violation by
using deb/ code in the generic simulation – and further we perform ugly
dynamic_cast to avoid breaking the ABI for nothing; aptitude is the only
other user of the simulation class according to codesearch.d.n and for
that our little trick works. It just isn't working if you happen to
extend pkgSimulate or otherwise manage to call the protected Go methods
directly – which isn't very realistic/practical.

1 files changed, 26 insertions, 23 deletions

diff --git a/apt-pkg/deb/dpkgpm.cc b/apt-pkg/deb/dpkgpm.cc
index d14155d01..4a49774f8 100644
--- a/apt-pkg/deb/dpkgpm.cc
+++ b/apt-pkg/deb/dpkgpm.cc
@@ -1297,37 +1297,34 @@ static void cleanUpTmpDir(char * const tmpdir)				/*{{{*/
  * through to human readable (and i10n-able)
  * names and calculates a percentage for each step.
  */
-bool pkgDPkgPM::Go(APT::Progress::PackageManager *progress)
+static bool ItemIsEssential(pkgDPkgPM::Item const &I)
+{
+   static auto const cachegen = _config->Find("pkgCacheGen::Essential");
+   if (cachegen == "none" || cachegen == "native")
+      return true;
+   if (unlikely(I.Pkg.end()))
+      return true;
+   return (I.Pkg->Flags & pkgCache::Flag::Essential) != 0;
+}
+bool pkgDPkgPM::ExpandPendingCalls(std::vector<Item> &List, pkgDepCache &Cache)
 {
-   // we remove the last configures (and after that removes) from the list here
-   // as they will be covered by the pending calls, so explicit calls are busy work
-   decltype(List)::const_iterator::difference_type explicitIdx =
-      std::distance(List.cbegin(),
-	    _config->FindB("Dpkg::ExplicitLastConfigure", false) ? List.cend() :
-	    std::find_if_not(
-	       std::find_if_not(List.crbegin(), List.crend(), [](Item const &i) { return i.Op == Item::Configure; }),
-	       List.crend(), [](Item const &i) { return i.Op == Item::Remove || i.Op == Item::Purge; }).base());
-
-   // explicitely remove everything for hookscripts and progress building
    {
       std::unordered_set<decltype(pkgCache::Package::ID)> alreadyRemoved;
       for (auto && I : List)
 	 if (I.Op == Item::Remove || I.Op == Item::Purge)
 	    alreadyRemoved.insert(I.Pkg->ID);
-      decltype(List) AppendList;
+      std::remove_reference<decltype(List)>::type AppendList;
       for (auto Pkg = Cache.PkgBegin(); Pkg.end() == false; ++Pkg)
 	 if (Cache[Pkg].Delete() && alreadyRemoved.insert(Pkg->ID).second == true)
 	    AppendList.emplace_back(Cache[Pkg].Purge() ? Item::Purge : Item::Remove, Pkg);
       std::move(AppendList.begin(), AppendList.end(), std::back_inserter(List));
    }
-
-   // explicitely configure everything for hookscripts and progress building
    {
       std::unordered_set<decltype(pkgCache::Package::ID)> alreadyConfigured;
       for (auto && I : List)
 	 if (I.Op == Item::Configure)
 	    alreadyConfigured.insert(I.Pkg->ID);
-      decltype(List) AppendList;
+      std::remove_reference<decltype(List)>::type AppendList;
       for (auto && I : List)
 	 if (I.Op == Item::Install && alreadyConfigured.insert(I.Pkg->ID).second == true)
 	    AppendList.emplace_back(Item::Configure, I.Pkg);
@@ -1336,15 +1333,21 @@ bool pkgDPkgPM::Go(APT::Progress::PackageManager *progress)
 	    AppendList.emplace_back(Item::Configure, Pkg);
       std::move(AppendList.begin(), AppendList.end(), std::back_inserter(List));
    }
+   return true;
+}
+bool pkgDPkgPM::Go(APT::Progress::PackageManager *progress)
+{
+   // we remove the last configures (and after that removes) from the list here
+   // as they will be covered by the pending calls, so explicit calls are busy work
+   decltype(List)::const_iterator::difference_type explicitIdx =
+      std::distance(List.cbegin(),
+	    _config->FindB("Dpkg::ExplicitLastConfigure", false) ? List.cend() :
+	    std::find_if_not(
+	       std::find_if_not(List.crbegin(), List.crend(), [](Item const &i) { return i.Op == Item::Configure; }),
+	       List.crend(), [](Item const &i) { return i.Op == Item::Remove || i.Op == Item::Purge; }).base());
 
-   auto const ItemIsEssential = [](pkgDPkgPM::Item const &I) {
-      static auto const cachegen = _config->Find("pkgCacheGen::Essential");
-      if (cachegen == "none" || cachegen == "native")
-	 return true;
-      if (unlikely(I.Pkg.end()))
-	 return true;
-      return (I.Pkg->Flags & pkgCache::Flag::Essential) != 0;
-   };
+   // explicitely remove&configure everything for hookscripts and progress building
+   ExpandPendingCalls(List, Cache);
 
    auto const StripAlreadyDoneFromPending = [&](APT::VersionVector & Pending) {
       Pending.erase(std::remove_if(Pending.begin(), Pending.end(), [&](pkgCache::VerIterator const &Ver) {