Merge branch 'feature/why' into 'main'

Introduce apt why, apt why-not

See merge request apt-team/apt!479

2 files changed, 23 insertions, 0 deletions

diff --git a/apt-pkg/solver3.cc b/apt-pkg/solver3.cc
index 620156ac3..abc0af314 100644
--- a/apt-pkg/solver3.cc
+++ b/apt-pkg/solver3.cc
@@ -1267,3 +1267,23 @@ bool APT::Solver::ToDepCache(pkgDepCache &depcache) const
    }
    return true;
 }
+
+// Command-line
+std::string APT::Solver::InternalCliWhy(pkgDepCache &cache, pkgCache::PkgIterator pkg, bool decision)
+{
+   APT::Solver solver(cache.GetCache(), cache.GetPolicy(), EDSP::Request::Flags(0));
+   // In case nothing has a positive dependency on pkg it may not actually be discovered in a `why-not`
+   // scenario, so make sure we discover it explicitly.
+   solver.Discover(Var(pkg));
+   if (not solver.FromDepCache(cache) || not solver.Solve())
+      return "";
+   std::unordered_set<Var> seen;
+   std::string buf;
+   if (solver[Var(pkg)].decision == Decision::NONE)
+      return strprintf(buf, "%s is undecided\n", pkg.FullName().c_str()), buf;
+   if (decision && solver[Var(pkg)].decision != Decision::MUST)
+      return strprintf(buf, "%s is not actually marked for install\n", pkg.FullName().c_str()), buf;
+   if (not decision && solver[Var(pkg)].decision == Decision::MUST)
+      return strprintf(buf, "%s is actually marked for install\n", pkg.FullName().c_str()), buf;
+   return solver.LongWhyStr(Var(pkg), decision, solver[Var(pkg)].reason, "", seen);
+}
diff --git a/apt-pkg/solver3.h b/apt-pkg/solver3.h
index 6810df426..43f6ec3a7 100644
--- a/apt-pkg/solver3.h
+++ b/apt-pkg/solver3.h
@@ -316,6 +316,9 @@ class Solver
     * \param seen A set of seen objects such that the output does not repeat itself (not for safety, it is acyclic)
     */
    std::string LongWhyStr(Var var, bool decision, const Clause *rclause, std::string prefix, std::unordered_set<Var> &seen) const;
+
+   // \brief Temporary internal API with external linkage for the `apt why` and `apt why-not` commands.
+   APT_PUBLIC static std::string InternalCliWhy(pkgDepCache &depcache, pkgCache::PkgIterator Pkg, bool decision);
 };
 
 }; // namespace APT