Step over empty sections in TagFiles with comments

Implementing a parser with recursion isn't the best idea, but in
practice we should get away with it for the time being to avoid
needless codechurn.

Closes: #920317 #921037

3 files changed, 76 insertions, 2 deletions

diff --git a/apt-pkg/tagfile.cc b/apt-pkg/tagfile.cc
index 98001afd1..1e7f2867c 100644
--- a/apt-pkg/tagfile.cc
+++ b/apt-pkg/tagfile.cc
@@ -250,8 +250,12 @@ bool pkgTagFile::Step(pkgTagSection &Tag)
       d->chunks.erase(d->chunks.begin(), first);
    }
 
-   Tag.Trim();
-   return true;
+   if ((d->Flags & pkgTagFile::SUPPORT_COMMENTS) == 0 || Tag.Count() != 0)
+   {
+      Tag.Trim();
+      return true;
+   }
+   return Step(Tag);
 }
 									/*}}}*/
 // TagFile::Fill - Top up the buffer					/*{{{*/
diff --git a/test/integration/test-apt-sources-deb822 b/test/integration/test-apt-sources-deb822
index fdf26fe97..8ffe0abe6 100755
--- a/test/integration/test-apt-sources-deb822
+++ b/test/integration/test-apt-sources-deb822
@@ -14,6 +14,8 @@ BASE='# some comment
 # that contains a : as well
 #Types: meep
 
+# a free-standing comment appears
+
 Types: deb
 #Types: deb-src
 URIs: http://ftp.debian.org/debian
@@ -291,3 +293,69 @@ testsuccessequal --nomsg "'http://ftp.debian.org/debian/dists/stable/InRelease'
 'http://ftp.debian.org/debian2/dists/sid/non-free/binary-powerpc/Packages.xz' ftp.debian.org_debian2_dists_sid_non-free_binary-powerpc_Packages 0 
 'http://ftp.debian.org/debian2/dists/sid/non-free/binary-all/Packages.xz' ftp.debian.org_debian2_dists_sid_non-free_binary-all_Packages 0 
 'http://ftp.debian.org/debian2/dists/sid/non-free/i18n/Translation-en.xz' ftp.debian.org_debian2_dists_sid_non-free_i18n_Translation-en 0 " aptget update --print-uris
+
+EXPECTEDUK="'http://ftp.uk.debian.org/debian/dists/stretch/InRelease' ftp.uk.debian.org_debian_dists_stretch_InRelease 0 
+'http://ftp.uk.debian.org/debian/dists/stretch/main/source/Sources.xz' ftp.uk.debian.org_debian_dists_stretch_main_source_Sources 0 
+'http://ftp.uk.debian.org/debian/dists/stretch/contrib/source/Sources.xz' ftp.uk.debian.org_debian_dists_stretch_contrib_source_Sources 0 
+'http://ftp.uk.debian.org/debian/dists/stretch/non-free/source/Sources.xz' ftp.uk.debian.org_debian_dists_stretch_non-free_source_Sources 0 
+'http://ftp.uk.debian.org/debian/dists/stretch/main/binary-i386/Packages.xz' ftp.uk.debian.org_debian_dists_stretch_main_binary-i386_Packages 0 
+'http://ftp.uk.debian.org/debian/dists/stretch/main/binary-all/Packages.xz' ftp.uk.debian.org_debian_dists_stretch_main_binary-all_Packages 0 
+'http://ftp.uk.debian.org/debian/dists/stretch/main/i18n/Translation-en.xz' ftp.uk.debian.org_debian_dists_stretch_main_i18n_Translation-en 0 
+'http://ftp.uk.debian.org/debian/dists/stretch/contrib/binary-i386/Packages.xz' ftp.uk.debian.org_debian_dists_stretch_contrib_binary-i386_Packages 0 
+'http://ftp.uk.debian.org/debian/dists/stretch/contrib/binary-all/Packages.xz' ftp.uk.debian.org_debian_dists_stretch_contrib_binary-all_Packages 0 
+'http://ftp.uk.debian.org/debian/dists/stretch/contrib/i18n/Translation-en.xz' ftp.uk.debian.org_debian_dists_stretch_contrib_i18n_Translation-en 0 
+'http://ftp.uk.debian.org/debian/dists/stretch/non-free/binary-i386/Packages.xz' ftp.uk.debian.org_debian_dists_stretch_non-free_binary-i386_Packages 0 
+'http://ftp.uk.debian.org/debian/dists/stretch/non-free/binary-all/Packages.xz' ftp.uk.debian.org_debian_dists_stretch_non-free_binary-all_Packages 0 
+'http://ftp.uk.debian.org/debian/dists/stretch/non-free/i18n/Translation-en.xz' ftp.uk.debian.org_debian_dists_stretch_non-free_i18n_Translation-en 0 "
+
+msgcleantest 'Test deb822 sources.list file comments' 'top'
+cat > $SOURCES <<EOF
+#NOTE: Most preferred source listed first!
+
+
+#=== NEW MULTI-LINE FORMAT ===============
+Types:          deb deb-src
+URIs:http://ftp.uk.debian.org/debian/
+Suites:         stretch
+Components:     main contrib non-free
+EOF
+testsuccessequal --nomsg "$EXPECTEDUK" aptget update --print-uris
+
+msgcleantest 'Test deb822 sources.list file comments' 'bottom'
+cat > $SOURCES <<EOF
+Types:          deb deb-src
+URIs:http://ftp.uk.debian.org/debian/
+Suites:         stretch
+Components:     main contrib non-free
+#=== NEW MULTI-LINE FORMAT ===============
+
+
+#NOTE: Most preferred source listed first!
+EOF
+testsuccessequal --nomsg "$EXPECTEDUK" aptget update --print-uris
+
+msgcleantest 'Test deb822 sources.list file comments' 'both'
+cat > $SOURCES <<EOF
+#=== NEW MULTI-LINE FORMAT ===============
+
+
+#NOTE: Most preferred source listed first!
+Types:          deb deb-src
+URIs:http://ftp.uk.debian.org/debian/
+Suites:         stretch
+Components:     main contrib non-free
+#=== NEW MULTI-LINE FORMAT ===============
+
+
+#NOTE: Most preferred source listed first!
+EOF
+testsuccessequal --nomsg "$EXPECTEDUK" aptget update --print-uris
+
+
+msgcleantest 'Test deb822 sources.list file comments' 'empty'
+cat > $SOURCES <<EOF
+#=== NEW MULTI-LINE FORMAT ===============
+
+
+EOF
+testempty aptget update --print-uris
diff --git a/test/libapt/tagfile_test.cc b/test/libapt/tagfile_test.cc
index f455a8dcc..8823ff781 100644
--- a/test/libapt/tagfile_test.cc
+++ b/test/libapt/tagfile_test.cc
@@ -232,6 +232,8 @@ TEST(TagFileTest, Comments)
    FileFd fd;
    createTemporaryFile("commentfile", fd, NULL, "# Leading comments should be ignored.\n"
 "\n"
+"# A wild second comment appears!\n"
+"\n"
 "Source: foo\n"
 "#Package: foo\n"
 "Section: bar\n"