get dpkg lock in build-dep if cache was invalid again

Regression introduced in a249b3e6fd798935a02b769149c9791a6fa6ef16, which
in the case of an invalid cache would build the first part unlocked and
later pick up the (still unlocked) cache for further processing, so the
system got never locked and apt would end up complaining about being
unable to release the lock at shutdown.

The far more common case of having a valid cache worked as expected and
hence covered up the problem – especially as tests who would have
noticed it are simulations only, which do not lock.

Closes: 814139
Reported-By: Balint Reczey <balint@balintreczey.hu>
Reported-By: Helmut Grohne <helmut@subdivi.de> on IRC

apt-pkg/cachefile.cc

@@ -238,6 +238,7 @@ bool pkgCacheFile::AddIndexFile(pkgIndexFile * const File)		/*{{{*/
       ExternOwner = false;
       Map = NULL;
    }
+   _system->UnLock(true);
    return true;
 }
 									/*}}}*/

apt-private/private-source.cc

@@ -73,8 +73,6 @@ static pkgSrcRecords::Parser *FindSrc(const char *Name,
 			       pkgSrcRecords &SrcRecs,std::string &Src,
 			       CacheFile &Cache)
 {
-   if (Cache.BuildCaches(false) == false)
-      return nullptr;
    std::string VerTag, UserRequestedVerTag;
    std::string ArchTag = "";
    std::string RelTag = _config->Find("APT::Default-Release");
@@ -321,12 +319,11 @@ bool DoSource(CommandLine &CmdL)
       return _error->Error(_("Must specify at least one package to fetch source for"));
 
    CacheFile Cache;
-   // Read the source list
-   if (Cache.BuildSourceList() == false)
+   if (Cache.BuildCaches(false) == false)
       return false;
-   pkgSourceList *List = Cache.GetSourceList();
 
    // Create the text record parsers
+   pkgSourceList * const List = Cache.GetSourceList();
    pkgSrcRecords SrcRecs(*List);
    if (_error->PendingError() == true)
       return false;
@@ -725,8 +722,11 @@ bool DoBuildDep(CommandLine &CmdL)
 	       VolatileCmdL.size());
    }
 
+   bool const WantLock = _config->FindB("APT::Get::Print-URIs", false) == false;
    if (CmdL.FileList[1] != 0)
    {
+      if (Cache.BuildCaches(WantLock) == false)
+	 return false;
       // Create the text record parsers
       pkgSrcRecords SrcRecs(*List);
       if (_error->PendingError() == true)
@@ -747,7 +747,6 @@ bool DoBuildDep(CommandLine &CmdL)
 
    Cache.AddIndexFile(new debStringPackageIndex(buildDepsPkgFile.str()));
 
-   bool WantLock = _config->FindB("APT::Get::Print-URIs", false) == false;
    if (Cache.Open(WantLock) == false)
       return false;
    pkgProblemResolver Fix(Cache.GetDepCache());

test/integration/test-bug-814139-pickup-of-different-cache-states

@@ -0,0 +1,58 @@
+#!/bin/sh
+set -e
+
+TESTDIR="$(readlink -f "$(dirname "$0")")"
+. "$TESTDIR/framework"
+
+setupenvironment
+configarchitecture 'amd64'
+
+insertinstalledpackage 'build-essential' 'amd64' '1'
+
+buildsimplenativepackage 'foo' 'all' '1' 'stable' 'Build-Depends: bar'
+buildsimplenativepackage 'bar' 'all' '1' 'stable'
+
+setupaptarchive
+
+cp rootdir/var/lib/dpkg/status status.backup
+
+testrun() {
+	cp status.backup rootdir/var/lib/dpkg/status
+	cleanup
+	testdpkgnotinstalled 'bar'
+	testsuccess aptget build-dep foo -y
+	testdpkginstalled 'bar'
+	cleanup
+	testsuccess aptget source foo
+	testsuccess test -s foo_1.tar.xz -a -s foo_1.dsc
+	rm foo_1.tar.xz foo_1.dsc
+	testsuccess test -d foo-1
+	rm -rf foo-1
+	cleanup
+	testsuccess aptget install foo -y
+}
+
+msgmsg 'Caches fully up-to-date'
+cleanup() {
+	rm -f rootdir/var/cache/apt/*.bin
+	testsuccess aptcache gencaches
+}
+testrun
+
+msgmsg 'pkgcache.bin is missing'
+cleanup() {
+	rm -f rootdir/var/cache/apt/*.bin
+	testsuccess aptcache gencaches
+	rm rootdir/var/cache/apt/pkgcache.bin
+}
+testrun
+
+msgmsg 'Caches are not writeable'
+rm rootdir/var/cache/apt/*.bin
+addtrap 'prefix' 'chmod 755 rootdir/var/cache/apt;'
+chmod 555 rootdir/var/cache/apt
+testsuccess aptcache gencaches
+cleanup() {
+	testfilestats "${TMPWORKINGDIRECTORY}/rootdir/var/cache/apt" '%a' '=' '555'
+}
+testrun