Implement Service.systemd_properties (#612)

This expose units informations from systemctl show

Also fix archlinux image reference from docker hub

Author: romainx

images/archlinux/Dockerfile

@@ -1,4 +1,4 @@
-FROM archlinux/base
+FROM archlinux/archlinux:base
 
 RUN pacman -Syu --noconfirm --noprogressbar --quiet python openssh iputils procps systemd systemd-sysvcompat && \
     systemctl enable sshd.service

test/test_modules.py

@@ -163,6 +163,17 @@ def test_service(host, name, running, enabled):
     service = host.service(name)
     assert service.is_running == running
     assert service.is_enabled == enabled
+    # check with systemd_properties
+    assert (
+        service.systemd_properties["UnitFileState"] == "enabled"
+        if enabled
+        else "disabled"
+    )
+    assert (
+        service.systemd_properties["ActiveState"] in ["active"]
+        if running
+        else ["failed", "inactive"]
+    )
 
 
 def test_salt(host):

testinfra/modules/service.py

@@ -47,7 +47,7 @@ def is_valid(self):
         """Test if service is valid
 
         This method is only available in the systemd implementation,
-        it will raise NotImplementedError in others implementation
+        it will raise ``NotImplementedError`` in others implementation
         """
         raise NotImplementedError
 
@@ -56,7 +56,27 @@ def is_masked(self):
         """Test if service is masked
 
         This method is only available in the systemd implementation,
-        it will raise NotImplementedError in others implementations
+        it will raise ``NotImplementedError`` in others implementations
+        """
+        raise NotImplementedError
+
+    @cached_property
+    def systemd_properties(self):
+        """Properties of the service (unit).
+
+        Return service properties as a `dict`,
+        empty properties are not returned.
+
+        >>> ntp = host.service("ntp")
+        >>> ntp.systemd_properties["FragmentPath"]
+        '/lib/systemd/system/ntp.service'
+
+        This method is only available in the systemd implementation,
+        it will raise ``NotImplementedError`` in others implementations
+
+        Note: based on `systemctl show`_
+
+        .. _systemctl show: https://man7.org/linux/man-pages/man1/systemctl.1.html
         """
         raise NotImplementedError
 
@@ -159,6 +179,17 @@ def is_masked(self):
         cmd = self.run_test("systemctl is-enabled %s", self.name)
         return cmd.stdout.strip() == "masked"
 
+    @cached_property
+    def systemd_properties(self):
+        out = self.check_output("systemctl show %s", self.name)
+        out_d = {}
+        if out:
+            # maxsplit is required because values can contain `=`
+            out_d = dict(
+                map(lambda pair: pair.split("=", maxsplit=1), out.splitlines())
+            )
+        return out_d
+
 
 class UpstartService(SysvService):
     @property