* apt-pkg/packagemanager.cc:

  - do not try to a void a breaks if the broken package pre-depends
    on the breaker, but let dpkg auto-deconfigure it

apt-pkg/packagemanager.cc

@@ -680,7 +680,6 @@ bool pkgPackageManager::SmartUnPack(PkgIterator Pkg, bool const Immediate, int c
 	 {
 	    VerIterator Ver(Cache,*I);
 	    PkgIterator BrokenPkg = Ver.ParentPkg();
-	    VerIterator InstallVer(Cache,Cache[BrokenPkg].InstallVer);
 	    if (BrokenPkg.CurrentVer() != Ver)
 	    {
 	       if (Debug)
@@ -695,20 +694,49 @@ bool pkgPackageManager::SmartUnPack(PkgIterator Pkg, bool const Immediate, int c
 		  // This dependancy has already been dealt with by another SmartUnPack on Pkg
 		  break;
 	       } else {
-		  // Found a break, so unpack the package,
+		  // Found a break, so see if we can unpack the package to avoid it
 		  // but do not set loop if another SmartUnPack already deals with it
-		  if (Debug)
+		  VerIterator InstallVer(Cache,Cache[BrokenPkg].InstallVer);
+		  bool circle = false;
+		  for (pkgCache::DepIterator D = InstallVer.DependsList(); D.end() == false; ++D)
+		  {
+		     if (D->Type != pkgCache::Dep::PreDepends)
+			continue;
+		     SPtrArray<Version *> VL = D.AllTargets();
+		     for (Version **I = VL; *I != 0; ++I)
+		     {
+			VerIterator V(Cache,*I);
+			PkgIterator P = V.ParentPkg();
+			// we are checking for installation as an easy 'protection' against or-groups and (unchosen) providers
+			if (P->CurrentVer == 0 || P != Pkg || (P.CurrentVer() != V && Cache[P].InstallVer != V))
+			   continue;
+			circle = true;
+			break;
+		     }
+		     if (circle == true)
+			break;
+		  }
+		  if (circle == true)
+		  {
+		     if (Debug)
+		        cout << OutputInDepth(Depth) << "  Avoiding " << End << " avoided as " << BrokenPkg.FullName() << " has a pre-depends on " << Pkg.FullName() << std::endl;
+		     continue;
+		  }
+		  else
 		  {
-		     cout << OutputInDepth(Depth) << "  Unpacking " << BrokenPkg.Name() << " to avoid " << End;
-		     if (PkgLoop == true)
-			cout << " (Looping)";
-		     cout << std::endl;
+		     if (Debug)
+		     {
+			cout << OutputInDepth(Depth) << "  Unpacking " << BrokenPkg.FullName() << " to avoid " << End;
+			if (PkgLoop == true)
+			   cout << " (Looping)";
+			cout << std::endl;
+		     }
+		     if (PkgLoop == false)
+			List->Flag(Pkg,pkgOrderList::Loop);
+		     SmartUnPack(BrokenPkg, false, Depth + 1);
+		     if (PkgLoop == false)
+			List->RmFlag(Pkg,pkgOrderList::Loop);
 		  }
-		  if (PkgLoop == false)
-		     List->Flag(Pkg,pkgOrderList::Loop);
-		  SmartUnPack(BrokenPkg, false, Depth + 1);
-		  if (PkgLoop == false)
-		     List->RmFlag(Pkg,pkgOrderList::Loop);
 	       }
 	    } else {
 	       // Check if a package needs to be removed

debian/changelog

@@ -40,6 +40,9 @@ apt (0.8.16~exp13) UNRELEASED; urgency=low
       e.g. in a Depends line and are now requested for removal
   * cmdline/apt-cache.cc:
     - correct --pre-depends option by using dash consistently (LP: #940837)
+  * apt-pkg/packagemanager.cc:
+    - do not try to a void a breaks if the broken package pre-depends
+      on the breaker, but let dpkg auto-deconfigure it
 
   [ Steve Langasek ]
   * cmdline/apt-get.cc:
@@ -62,7 +65,7 @@ apt (0.8.16~exp13) UNRELEASED; urgency=low
   * apt-pkg/contrib/fileutl.h:
     - fix compat with FileFd::OpenDescriptor() in ReadOnlyGzip mode
 
- -- David Kalnischkies <kalnischkies@gmail.com>  Sat, 25 Feb 2012 19:43:04 +0100
+ -- David Kalnischkies <kalnischkies@gmail.com>  Sat, 03 Mar 2012 11:03:58 +0100
 
 apt (0.8.16~exp12) experimental; urgency=low
 

test/integration/skip-avoid-avoiding-breaks-predepends

@@ -0,0 +1,21 @@
+#!/bin/sh
+set -e
+
+TESTDIR=$(readlink -f $(dirname $0))
+. $TESTDIR/framework
+setupenvironment
+configarchitecture 'native'
+
+insertinstalledpackage 'looping' 'native' '1'
+insertinstalledpackage 'loop1' 'native' '1' 'Depends: loop2 (= 1)'
+insertinstalledpackage 'loop2' 'native' '1' 'Depends: loop1 (= 1)'
+
+buildsimplenativepackage 'looping' 'native' '1.15.7.2' 'stable' 'Breaks: loop2 (<= 1)'
+buildsimplenativepackage 'loop1' 'native' '2' 'stable' 'Depends: loop2 (= 2)'
+buildsimplenativepackage 'loop2' 'native' '2' 'stable' 'Depends: loop1 (= 2)
+Pre-Depends: looping (>= 1.15)'
+
+setupaptarchive
+
+aptget dist-upgrade -y -o Debug::pkgOrderList=1 #-qq 2>&1 > /dev/null
+testdpkginstalled looping loop1 loop2