From 8f317d97c9fb821e839342ae445c824207678eb7 Mon Sep 17 00:00:00 2001
From: Julian Andres Klode <julian.klode@canonical.com>
Date: Sat, 2 Nov 2024 12:45:07 +0100
Subject: solver3: Reject all non-candidates outright for strict pinning

Reimplement strict pinning by rejecting the non-candidates when
translating the problem from the depcache to the solver. This is
substantially better than restricting the list of alternatives for
an or group to only include allowed ones for debugging purposes,
albeit a bit slower.
---
 apt-pkg/solver3.cc | 43 ++++++++++++++++++-------------------------
 1 file changed, 18 insertions(+), 25 deletions(-)

(limited to 'apt-pkg/solver3.cc')

diff --git a/apt-pkg/solver3.cc b/apt-pkg/solver3.cc
index 83f3359df..00663ddca 100644
--- a/apt-pkg/solver3.cc
+++ b/apt-pkg/solver3.cc
@@ -329,9 +329,6 @@ 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;
@@ -369,12 +366,9 @@ bool APT::Solver::Install(pkgCache::PkgIterator Pkg, Var reason, Group group)
    Work workItem{Var(Pkg), depth(), group};
    for (auto ver = Pkg.VersionList(); not ver.end(); ver++)
    {
-      if (IsAllowedVersion(ver))
-      {
-	 workItem.solutions.push_back(ver);
-	 if ((*this)[ver].decision != Decision::MUSTNOT)
-	    anyInstallable = true;
-      }
+      workItem.solutions.push_back(ver);
+      if ((*this)[ver].decision != Decision::MUSTNOT)
+	 anyInstallable = true;
    }
 
    if (not anyInstallable)
@@ -535,8 +529,7 @@ bool APT::Solver::EnqueueOrGroup(pkgCache::DepIterator start, pkgCache::DepItera
 	 {
 	    if (unlikely(debug >= 3))
 	       std::cerr << "Adding work to  item " << Ver.ParentPkg().FullName() << "=" << Ver.VerStr() << " -> " << tgti.ParentPkg().FullName() << "=" << tgti.VerStr() << "\n";
-	    if (IsAllowedVersion(*tgt))
-	       workItem.solutions.push_back(*tgt);
+	    workItem.solutions.push_back(*tgt);
 	 }
       }
       delete[] all;
@@ -572,7 +565,7 @@ bool APT::Solver::EnqueueOrGroup(pkgCache::DepIterator start, pkgCache::DepItera
 	    newOptional = false, wasImportant = policy.IsImportantDep(D);
 
       bool satisfied = std::any_of(workItem.solutions.begin(), workItem.solutions.end(), [this](auto ver)
-				   { return pkgCache::VerIterator(cache, ver).ParentPkg()->CurrentVer != 0; });
+				   { return pkgCache::VerIterator(cache, ver).ParentPkg().CurrentVer() == ver; });
 
       if (important && wasImportant && not newOptional && not satisfied)
       {
@@ -696,17 +689,6 @@ bool APT::Solver::RejectReverseDependencies(pkgCache::VerIterator Ver)
    return true;
 }
 
-bool APT::Solver::IsAllowedVersion(pkgCache::Version *V)
-{
-   pkgCache::VerIterator ver(cache, V);
-   if (not StrictPinning || ver.ParentPkg().CurrentVer() == ver || policy.GetCandidateVer(ver.ParentPkg()) == ver || (*this)[V].decision == Decision::MUST)
-      return true;
-
-   if (unlikely(debug >= 3))
-      std::cerr << "Ignoring: " << ver.ParentPkg().FullName() << "=" << ver.VerStr() << "(neither candidate nor installed)\n";
-   return false;
-}
-
 void APT::Solver::Push(Work work)
 {
    if (unlikely(debug >= 2))
@@ -943,6 +925,18 @@ bool APT::Solver::FromDepCache(pkgDepCache &depcache)
    bool AllowRemoveManual = AllowRemove && _config->FindB("APT::Solver::RemoveManual", false);
    DefaultRootSetFunc2 rootSet(&cache);
 
+   // Enforce strict pinning rules by rejecting all forbidden versions.
+   if (StrictPinning)
+   {
+      for (auto P = cache.PkgBegin(); not P.end(); P++)
+      {
+	 for (auto V = P.VersionList(); not V.end(); ++V)
+	    if (P.CurrentVer() != V && depcache.GetCandidateVersion(P) != V)
+	       if (not Enqueue(Var(V), false, {}))
+		  return false;
+      }
+   }
+
    for (auto P = cache.PkgBegin(); not P.end(); P++)
    {
       if (P->VersionList == nullptr)
@@ -997,8 +991,7 @@ bool APT::Solver::FromDepCache(pkgDepCache &depcache)
 	 {
 	    Work w{Var(), depth(), Group, isOptional, Upgrade};
 	    for (auto V = P.VersionList(); not V.end(); ++V)
-	       if (IsAllowedVersion(V))
-		  w.solutions.push_back(V);
+	       w.solutions.push_back(V);
 	    std::stable_sort(w.solutions.begin(), w.solutions.end(), CompareProviders3{cache, policy, P, *this});
 	    AddWork(std::move(w));
 	 }
-- 
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