Add Archlinux support

This commit adds archlinux support to bindep. It uses the pacman
package manager's query interface to determine if the packages are
installed.

Change-Id: Idf69042b9072a2943f14ae9469cd42a252cc6b82

bindep/depends.py

@@ -205,6 +205,9 @@ class Depends(object):
         elif distro in ["gentoo"]:
             atoms.add("emerge")
             self.platform = Emerge()
+        elif distro in ["arch"]:
+            atoms.add("pacman")
+            self.platform = Pacman()
         return ["platform:%s" % (atom,) for atom in sorted(atoms)]
 
 
@@ -294,6 +297,27 @@ class Emerge(Platform):
         return elements[0]
 
 
+class Pacman(Platform):
+    """pacman specific implementation.
+
+    This shells out to pacman
+    """
+
+    def get_pkg_version(self, pkg_name):
+        try:
+            output = subprocess.check_output(
+                ['pacman', '-Q', pkg_name],
+                stderr=subprocess.STDOUT)
+        except subprocess.CalledProcessError as e:
+            if e.returncode == 1 and e.output.endswith('was not found'):
+                return None
+            raise
+        # output looks like
+        # version
+        elements = output.strip().split(' ')
+        return elements[1]
+
+
 def _eval_diff(operator, diff):
     """Return the boolean result for operator given diff.
 

bindep/tests/test_depends.py

@@ -31,6 +31,7 @@ from bindep.depends import _eval
 from bindep.depends import Depends
 from bindep.depends import Dpkg
 from bindep.depends import Emerge
+from bindep.depends import Pacman
 from bindep.depends import Rpm
 
 
@@ -145,6 +146,13 @@ class TestDepends(TestCase):
                 depends.platform_profiles(), Contains("platform:dpkg"))
             self.assertIsInstance(depends.platform, Dpkg)
 
+    def test_arch_implies_pacman(self):
+        with self._mock_lsb("Arch"):
+            depends = Depends("")
+            self.assertThat(
+                depends.platform_profiles(), Contains("platform:pacman"))
+            self.assertIsInstance(depends.platform, Pacman)
+
     def test_finds_profiles(self):
         depends = Depends(dedent("""\
             foo
@@ -411,6 +419,36 @@ class TestEmerge(TestCase):
             stderr=subprocess.STDOUT)
 
 
+class TestPacman(TestCase):
+
+    def test_unknown_package(self):
+        platform = Pacman()
+
+        def _side_effect_raise(*args, **kwargs):
+            raise subprocess.CalledProcessError(
+                1, [], "error: package 'foo' was not found")
+
+        mock_checkoutput = self.useFixture(
+            fixtures.MockPatchObject(subprocess, "check_output")).mock
+        mock_checkoutput.side_effect = _side_effect_raise
+
+        self.assertEqual(None, platform.get_pkg_version("foo"))
+        mock_checkoutput.assert_called_once_with(
+            ['pacman', '-Q', 'foo'],
+            stderr=subprocess.STDOUT)
+        self.assertEqual(None, platform.get_pkg_version("foo"))
+
+    def test_installed_version(self):
+        platform = Pacman()
+        mock_checkoutput = self.useFixture(
+            fixtures.MockPatchObject(subprocess, "check_output")).mock
+        mock_checkoutput.return_value = 'foo 4.0.0-2'
+        self.assertEqual("4.0.0-2", platform.get_pkg_version("foo"))
+        mock_checkoutput.assert_called_once_with(
+            ['pacman', '-Q', 'foo'],
+            stderr=subprocess.STDOUT)
+
+
 class TestRpm(TestCase):
 
     # NOTE: test_not_installed is not implemented as rpm seems to only be aware