[Telemetry] discover.DiscoverClasses() does not add inheritted classes.

If a PageAction inherits another PageAction class, then DiscoverClasses() 
might mess up the map from simple module name to class object name. See 
bug for more details.

BUG=281568

Review URL: https://chromiumcodereview.appspot.com/23602015

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@220649 0039d316-1c4b-4281-b951-d872f2087c98

tools/telemetry/telemetry/core/discover.py

@@ -50,6 +50,8 @@ def DiscoverClasses(start_dir, top_level_dir, base_class, pattern='*',
                     index_by_class_name=False):
   """Discover all classes in |start_dir| which subclass |base_class|.
 
+  Base classes that contain subclasses are ignored by default.
+
   Args:
     start_dir: The directory to recursively search.
     top_level_dir: The top level of the package, for importing.
@@ -66,7 +68,8 @@ def DiscoverClasses(start_dir, top_level_dir, base_class, pattern='*',
   for module in modules:
     for _, obj in inspect.getmembers(module):
       if (inspect.isclass(obj) and obj is not base_class and
-          issubclass(obj, base_class)):
+          issubclass(obj, base_class) and obj.__module__ == module.__name__
+          and len(obj.__subclasses__()) == 0):
         if index_by_class_name:
           key_name = camel_case.ToUnderscore(obj.__name__)
         else:

tools/telemetry/telemetry/core/discover_unittest.py

@@ -14,11 +14,10 @@ class DiscoverTest(unittest.TestCase):
     base_class = Exception
     classes = discover.DiscoverClasses(start_dir, base_dir, base_class)
     self.assertTrue(len(classes) > 0)
-
-    found_dummy_exception = False
     for c in classes.values():
-      if c.__name__ == 'DummyException':
-        found_dummy_exception = True
       self.assertTrue(issubclass(c, Exception))
 
-    self.assertTrue(found_dummy_exception)
+    # discover_dummyclass is a base class and should not show up.
+    self.assertFalse('discover_dummyclass' in classes)
+    self.assertEqual(classes['another_discover_dummyclass'].__name__,
+                     'AnotherDummyException')

tools/telemetry/unittest_data/discoverable_classes/another_discover_dummyclass.py

+# Copyright 2013 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""Another dummy exception subclasses used by core/discover.py's unit tests."""
+
+# Import class instead of module explicitly so that inspect.getmembers() returns
+# two Exception subclasses in this current file.
+# Suppress complaints about unable to import class.  The directory path is
+# added at runtime by telemetry test runner.
+#pylint: disable=F0401
+from discoverable_classes.discover_dummyclass import DummyException
+
+
+class AnotherDummyException(DummyException):
+  pass