Add a GetCodeOwnersClient method.

GetCodeOwnersClient will return a GerritClient instance
if code-owners is enabled for the host, and will fall
back to DepotToolsClient otherwise.

Change-Id: I303147f36cb28ae3a40649fee020e6ea459b2c73
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2676989
Reviewed-by: Gavin Mak <gavinmak@google.com>
Reviewed-by: Josip Sokcevic <sokcevic@google.com>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>

gerrit_util.py

@@ -771,6 +771,13 @@ def SetCommitMessage(host, change, description, notify='ALL'):
         'in change %s' % change)
 
 
+def IsCodeOwnersEnabled(host):
+  """Check if the code-owners plugin is enabled for the host."""
+  path = 'config/server/capabilities'
+  capabilities = ReadHttpJsonResponse(CreateHttpConn(host, path))
+  return 'code-owners-checkCodeOwner' in capabilities
+
+
 def GetOwnersForFile(host, project, branch, path, limit=100,
                      o_params=('DETAILS',)):
   """Gets information about owners attached to a file."""

owners_client.py

@@ -213,3 +213,13 @@ class GerritClient(OwnersClient):
     data = gerrit_util.GetOwnersForFile(
         self._host, self._project, self._branch, path)
     return [d['account']['email'] for d in data['code_owners']]
+
+
+def GetCodeOwnersClient(root, host, project, branch):
+  """Get a new OwnersClient.
+
+  Defaults to GerritClient, and falls back to DepotToolsClient if code-owners
+  plugin is not available."""
+  if gerrit_util.IsCodeOwnersEnabled(host):
+    return GerritClient(host, project, branch)
+  return DepotToolsClient(root, branch)

tests/owners_client_test.py

@@ -48,7 +48,6 @@ def _get_owners():
   }
 
 
-
 class DepotToolsClientTest(unittest.TestCase):
   def setUp(self):
     self.repo = filesystem_mock.MockFileSystem(files={
@@ -264,5 +263,23 @@ class OwnersClientTest(unittest.TestCase):
             ['bar/everyone/foo.txt', 'bar/everyone/bar.txt', 'bar/foo/']))
 
 
+class GetCodeOwnersClientTest(unittest.TestCase):
+  def setUp(self):
+    mock.patch('gerrit_util.IsCodeOwnersEnabled').start()
+    self.addCleanup(mock.patch.stopall)
+
+  def testGetCodeOwnersClient_GerritClient(self):
+    gerrit_util.IsCodeOwnersEnabled.return_value = True
+    self.assertIsInstance(
+        owners_client.GetCodeOwnersClient('root', 'host', 'project', 'branch'),
+        owners_client.GerritClient)
+
+  def testGetCodeOwnersClient_DepotToolsClient(self):
+    gerrit_util.IsCodeOwnersEnabled.return_value = False
+    self.assertIsInstance(
+        owners_client.GetCodeOwnersClient('root', 'host', 'project', 'branch'),
+        owners_client.DepotToolsClient)
+
+
 if __name__ == '__main__':
   unittest.main()