Dpkg::Deps: Fix implications evaluation to use arch qualifiers

When evaluating implications, it's important to take into account the
arch qualifier otherwise the dependency simplification code might strip
dependencies that cannot be stripped without altering the meaning
of the dependency.

Sponsored-by: Linaro Limited

scripts/Dpkg/Deps.pm

@@ -125,6 +125,29 @@ sub _arch_is_superset {
     return 1;
 }
 
+# Dpkg::Deps::_arch_qualifier_allows_implication($p, $q)
+#
+# Returns true if the arch qualifier $p and $q are compatible with the
+# implication $p -> $q, false otherwise. $p/$q can be
+# undef/"any"/"native" or an architecture string.
+
+sub _arch_qualifier_allows_implication {
+    my ($p, $q) = @_;
+    if (defined $p and $p eq "any") {
+	return 1 if defined $q and $q eq "any";
+	return 0;
+    } elsif (defined $p and $p eq "native") {
+	return 1 if defined $q and ($q eq "any" or $q eq "native");
+	return 0;
+    } elsif (defined $p) {
+	return 1 if defined $q and ($p eq $q or $q eq "any");
+	return 0;
+    } else {
+	return 0 if defined $q and $q ne "any" and $q ne "native";
+	return 1;
+    }
+}
+
 =item deps_eval_implication($rel_p, $v_p, $rel_q, $v_q)
 
 ($rel_p, $v_p) and ($rel_q, $v_q) express two dependencies as (relation,
@@ -598,6 +621,11 @@ sub implies {
 	# o, otherwise we can't conclude anything.
 	return undef unless Dpkg::Deps::_arch_is_superset($self->{arches}, $o->{arches});
 
+	# The arch qualifier must not forbid an implication
+	return undef unless
+	    Dpkg::Deps::_arch_qualifier_allows_implication($self->{archqual},
+	                                                   $o->{archqual});
+
 	# If o has no version clause, then our dependency is stronger
 	return 1 if not defined $o->{relation};
 	# If o has a version clause, we must also have one, otherwise there

scripts/t/400_Dpkg_Deps.t

@@ -13,7 +13,7 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-use Test::More tests => 18;
+use Test::More tests => 20;
 
 use strict;
 use warnings;
@@ -41,6 +41,14 @@ my $dep_or2 = deps_parse("x|y|a|b|c (<= 0.5)|c (>=1.5)|d|e");
 is($dep_or1->implies($dep_or2), 1, "Implication between OR 1/2");
 is($dep_or2->implies($dep_or1), undef, "Implication between OR 2/2");
 
+my $dep_ma_any = deps_parse("libcairo2:any");
+my $dep_ma_native = deps_parse("libcairo2");
+#my $dep_ma_native2 = deps_parse("libcairo2:native");
+is($dep_ma_native->implies($dep_ma_any), 1, "foo -> foo:any");
+#is($dep_ma_native2->implies($dep_ma_any), 1, "foo:native -> foo:any");
+is($dep_ma_any->implies($dep_ma_native), undef, "foo:any !-> foo");
+#is($dep_ma_any->implies($dep_ma_native2), undef, "foo:any !-> foo:native");
+
 my $field_arch = "libc6 (>= 2.5) [!alpha !hurd-i386], libc6.1 [alpha], libc0.1 [hurd-i386]";
 my $dep_i386 = deps_parse($field_arch, reduce_arch => 1, host_arch => 'i386');
 my $dep_alpha = deps_parse($field_arch, reduce_arch => 1, host_arch => 'alpha');