Allow parsing an empty Provides linemain

If dpkg-gencontrol was involved in the creation of a package we will not
usually encounter empty or otherwise useless fields, but apparently not
everyone is using it.

It isn't recommended to have these empty lines, but it isn't too hard to
ignore for Provides as we did for dependencies already and apt-ftparchive
can be convinced to produce empty files (if you feed it such a package)
as well, so lets be nice and provide users with a more accepting parser.

Closes: #1069874

3 files changed, 64 insertions, 3 deletions

diff --git a/apt-pkg/deb/deblistparser.cc b/apt-pkg/deb/deblistparser.cc
index 071189b04..9177d54f4 100644
--- a/apt-pkg/deb/deblistparser.cc
+++ b/apt-pkg/deb/deblistparser.cc
@@ -887,7 +887,7 @@ bool debListParser::ParseProvides(pkgCache::VerIterator &Ver)
    bool const barbarianArch = not APT::Configuration::checkArchitecture(Arch);
    const char *Start;
    const char *Stop;
-   if (Section.Find(pkgTagSection::Key::Provides,Start,Stop) == true)
+   if (Section.Find(pkgTagSection::Key::Provides,Start,Stop) && Start != Stop)
    {
       StringView Package;
       StringView Version;
diff --git a/test/integration/framework b/test/integration/framework
index de280cb8d..98fd7710a 100644
--- a/test/integration/framework
+++ b/test/integration/framework
@@ -882,8 +882,12 @@ buildsimplenativepackage() {
                     cp -ar "$FILE_TREE" "${BUILDDIR}/debian/tmp"
                 fi
 
-		(cd "${BUILDDIR}"; dpkg-gencontrol -DArchitecture=$arch)
-		(cd "${BUILDDIR}/debian/tmp"; md5sum $(find usr/ -type f) > DEBIAN/md5sums)
+		if [ ! -e "${BUILDDIR}/debian/tmp/DEBIAN/control" ]; then
+			(cd "${BUILDDIR}"; dpkg-gencontrol -DArchitecture=$arch)
+		fi
+		if [ ! -e "${BUILDDIR}/debian/tmp/DEBIAN/md5sums" ]; then
+			(cd "${BUILDDIR}/debian/tmp"; md5sum $(find usr/ -type f) > DEBIAN/md5sums)
+		fi
 		local LOG="${BUILDDIR}/../${NAME}_${VERSION}_${arch}.dpkg-deb.log"
 		# ensure the right permissions as dpkg-deb insists
 		chmod 755 "${BUILDDIR}/debian/tmp/DEBIAN"
diff --git a/test/integration/test-bug-1069874-working-with-not-normalized-packages b/test/integration/test-bug-1069874-working-with-not-normalized-packages
new file mode 100755
index 000000000..d45acee67
--- /dev/null
+++ b/test/integration/test-bug-1069874-working-with-not-normalized-packages
@@ -0,0 +1,57 @@
+#!/bin/sh
+set -e
+
+TESTDIR="$(readlink -f "$(dirname "$0")")"
+. "$TESTDIR/framework"
+setupenvironment
+configarchitecture 'amd64'
+
+WORKDIR="${TMPWORKINGDIRECTORY}/badcontrol"
+mkdir -p "${WORKDIR}/DEBIAN"
+cat > "${WORKDIR}/DEBIAN/control" << EOF
+Package: perccli
+Version: 007.2616.0000.0000
+Section: perccli
+Priority: optional
+Architecture: all
+Depends: 
+Pre-Depends: 
+Recommends: 
+Suggests: 
+Installed-Size: 7000
+Maintainer: Jane Doe <foo@example.org>
+Conflicts: 
+Replaces: 
+Provides: 
+Description: Not a real package
+EOF
+buildsimplenativepackage 'perccli' 'all' '007.2616.0000.0000' 'stable' '' '' '' '' "${WORKDIR}/DEBIAN"
+cp -a "${WORKDIR}/DEBIAN/control" aptarchive/Packages
+rm -rf "$WORKDIR"
+
+setupaptarchive --no-update
+echo "deb [trusted=yes] file:${TMPWORKINGDIRECTORY}/aptarchive ./" > rootdir/etc/apt/sources.list.d/00badcontrol.list
+testsuccess apt update
+
+# uses the flat Packages file which includes the line ending spaces
+testsuccess aptcache show perccli
+cp -a rootdir/tmp/testsuccess.output perccli.show
+testsuccessequal '4' grep -c '^\(\(Pre-\|\)Depends\|Provides\|Replaces\): \+$' perccli.show
+
+testdpkgnotinstalled perccli
+testsuccess apt install perccli
+testdpkginstalled perccli
+
+testsuccess apt policy perccli
+cp -a rootdir/tmp/testsuccess.output perccli.policy
+testsuccessequal '3' grep -c '7\.2616\.' perccli.policy
+
+# apt-ftparchive outputs empty fields, but not the space ending
+testsuccess rm rootdir/var/lib/apt/lists/*_._Packages
+testsuccess aptcache show perccli/now
+cp -a rootdir/tmp/testsuccess.output perccli.show
+testsuccessequal '4' grep -c '^\(\(Pre-\|\)Depends\|Provides\|Replaces\):$' perccli.show
+
+testsuccess apt policy perccli
+cp -a rootdir/tmp/testsuccess.output perccli.policy
+testsuccessequal '3' grep -c '7\.2616\.' perccli.policy