Try again to land the improved owners algorithm.

Initially landed in r173784, reverted in r173808

R=maruel@chromium.org
BUG=76727


Review URL: https://chromiumcodereview.appspot.com/11645009

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@173979 0039d316-1c4b-4281-b951-d872f2087c98

owners.py

@@ -49,6 +49,7 @@ Examples for all of these combinations can be found in tests/owners_unittest.py.
 """
 
 import collections
+import random
 import re
 
 
@@ -252,60 +253,60 @@ class Database(object):
           ('%s is not a "set" directive, "*", '
            'or an email address: "%s"' % (line_type, directive)))
 
-
   def _covering_set_of_owners_for(self, files):
-    # Get the set of directories from the files.
-    dirs = set()
-    for f in files:
-      dirs.add(self._enclosing_dir_with_owners(f))
-
-
-    owned_dirs = {}
-    dir_owners = {}
-
+    dirs_remaining = set(self._enclosing_dir_with_owners(f) for f in files)
+    all_possible_owners = self._all_possible_owners(dirs_remaining)
+    suggested_owners = set()
+    while dirs_remaining:
+      owner = self.lowest_cost_owner(all_possible_owners, dirs_remaining)
+      suggested_owners.add(owner)
+      for dirname, _ in all_possible_owners[owner]:
+        dirs_remaining.remove(dirname)
+    return suggested_owners
+
+  def _all_possible_owners(self, dirs):
+    """Returns a list of (potential owner, distance-from-dir) tuples; a
+    distance of 1 is the lowest/closest possible distance (which makes the
+    subsequent math easier)."""
+    all_possible_owners = {}
     for current_dir in dirs:
-      # Get the list of owners for each directory.
-      current_owners = set()
       dirname = current_dir
-      while dirname in self.owners_for:
-        current_owners |= self.owners_for[dirname]
+      distance = 1
+      while True:
+        for owner in self.owners_for.get(dirname, []):
+          all_possible_owners.setdefault(owner, [])
+          # It's possible the same owner might match a directory from
+          # multiple files, and we only want the closest entry.
+          if not any(current_dir == el[0] for el in all_possible_owners[owner]):
+            all_possible_owners[owner].append((current_dir, distance))
         if self._stop_looking(dirname):
           break
-        prev_parent = dirname
         dirname = self.os_path.dirname(dirname)
-        if prev_parent == dirname:
-          break
-
-      # Map each directory to a list of its owners.
-      dir_owners[current_dir] = current_owners
-
-      # Add the directory to the list of each owner.
-      for owner in current_owners:
-        owned_dirs.setdefault(owner, set()).add(current_dir)
-
-    final_owners = set()
-    while dirs:
-      # Find the owner that has the most directories.
-      max_count = 0
-      max_owner = None
-      owner_count = {}
-      for dirname in dirs:
-        for owner in dir_owners[dirname]:
-          count = owner_count.get(owner, 0) + 1
-          owner_count[owner] = count
-          if count >= max_count:
-            max_owner = owner
-            max_count = count
-
-      # If no more directories have OWNERS, we're done.
-      if not max_owner:
-        break
-
-      final_owners.add(max_owner)
-
-      # Remove all directories owned by the current owner from the remaining
-      # list.
-      for dirname in owned_dirs[max_owner]:
-        dirs.discard(dirname)
-
-    return final_owners
+        distance += 1
+    return all_possible_owners
+
+  @staticmethod
+  def lowest_cost_owner(all_possible_owners, dirs):
+    # We want to minimize both the number of reviewers and the distance
+    # from the files/dirs needing reviews. The "pow(X, 1.75)" below is
+    # an arbitrarily-selected scaling factor that seems to work well - it
+    # will select one reviewer in the parent directory over three reviewers
+    # in subdirs, but not one reviewer over just two.
+    total_costs_by_owner = {}
+    for owner in all_possible_owners:
+      total_distance = 0
+      num_directories_owned = 0
+      for dirname, distance in all_possible_owners[owner]:
+        if dirname in dirs:
+          total_distance += distance
+          num_directories_owned += 1
+        if num_directories_owned:
+          total_costs_by_owner[owner] = (total_distance /
+                                         pow(num_directories_owned, 1.75))
+
+    # Return the lowest cost owner. In the case of a tie, pick one randomly.
+    lowest_cost = min(total_costs_by_owner.itervalues())
+    lowest_cost_owners = filter(
+      lambda owner: total_costs_by_owner[owner] == lowest_cost,
+      total_costs_by_owner)
+    return random.Random().choice(lowest_cost_owners)

tests/owners_unittest.py

@@ -40,6 +40,8 @@ def test_repo():
     '/OWNERS': owners_file(owners.EVERYONE),
     '/base/vlog.h': '',
     '/chrome/OWNERS': owners_file(ben, brett),
+    '/chrome/browser/OWNERS': owners_file(brett),
+    '/chrome/browser/defaults.h': '',
     '/chrome/gpu/OWNERS': owners_file(ken),
     '/chrome/gpu/gpu_channel.h': '',
     '/chrome/renderer/OWNERS': owners_file(peter),
@@ -58,7 +60,7 @@ def test_repo():
   })
 
 
-class OwnersDatabaseTest(unittest.TestCase):
+class _BaseTestCase(unittest.TestCase):
   def setUp(self):
     self.repo = test_repo()
     self.files = self.repo.files
@@ -73,6 +75,8 @@ class OwnersDatabaseTest(unittest.TestCase):
     glob = glob or self.glob
     return owners.Database(root, fopen, os_path, glob)
 
+
+class OwnersDatabaseTest(_BaseTestCase):
   def test_constructor(self):
     self.assertNotEquals(self.db(), None)
 
@@ -205,16 +209,41 @@ class OwnersDatabaseTest(unittest.TestCase):
     self.assertRaises(owners.SyntaxErrorInOwnersFile,
         self.db().directories_not_covered_by, ['DEPS'], [brett])
 
-  def assert_reviewers_for(self, files, expected_reviewers):
+  def assert_syntax_error(self, owners_file_contents):
+    db = self.db()
+    self.files['/foo/OWNERS'] = owners_file_contents
+    self.files['/foo/DEPS'] = ''
+    try:
+      db.reviewers_for(['foo/DEPS'])
+      self.fail()  # pragma: no cover
+    except owners.SyntaxErrorInOwnersFile, e:
+      self.assertTrue(str(e).startswith('/foo/OWNERS:1'))
+
+  def test_syntax_error__unknown_token(self):
+    self.assert_syntax_error('{}\n')
+
+  def test_syntax_error__unknown_set(self):
+    self.assert_syntax_error('set myfatherisbillgates\n')
+
+  def test_syntax_error__bad_email(self):
+    self.assert_syntax_error('ben\n')
+
+
+class ReviewersForTest(_BaseTestCase):
+  def assert_reviewers_for(self, files, *potential_suggested_reviewers):
     db = self.db()
-    self.assertEquals(db.reviewers_for(set(files)), set(expected_reviewers))
+    suggested_reviewers = db.reviewers_for(set(files))
+    self.assertTrue(suggested_reviewers in
+        [set(suggestion) for suggestion in potential_suggested_reviewers])
 
   def test_reviewers_for__basic_functionality(self):
     self.assert_reviewers_for(['chrome/gpu/gpu_channel.h'],
-                             [brett])
+                              [ken])
 
   def test_reviewers_for__set_noparent_works(self):
-    self.assert_reviewers_for(['content/content.gyp'], [darin])
+    self.assert_reviewers_for(['content/content.gyp'],
+                              [john],
+                              [darin])
 
   def test_reviewers_for__valid_inputs(self):
     db = self.db()
@@ -236,15 +265,16 @@ class OwnersDatabaseTest(unittest.TestCase):
     self.assert_reviewers_for([
         'chrome/gpu/gpu_channel.h',
         'content/baz/froboz.h',
-        'chrome/renderer/gpu/gpu_channel_host.h'], [brett])
+        'chrome/renderer/gpu/gpu_channel_host.h'],
+        [brett])
 
   def test_reviewers_for__two_owners(self):
     self.assert_reviewers_for([
         'chrome/gpu/gpu_channel.h',
         'content/content.gyp',
         'content/baz/froboz.h',
-        'content/views/pie.h'
-        ], [john, brett])
+        'content/views/pie.h'],
+        [ken, john])
 
   def test_reviewers_for__all_files(self):
     self.assert_reviewers_for([
@@ -254,32 +284,100 @@ class OwnersDatabaseTest(unittest.TestCase):
         'content/content.gyp',
         'content/bar/foo.cc',
         'content/baz/froboz.h',
-        'content/views/pie.h'], [john, brett])
+        'content/views/pie.h'],
+        [peter, ken, john])
 
   def test_reviewers_for__per_file_owners_file(self):
     self.files['/content/baz/OWNERS'] = owners_file(lines=[
         'per-file ugly.*=tom@example.com'])
-    self.assert_reviewers_for(['content/baz/OWNERS'], [darin])
-
-  def assert_syntax_error(self, owners_file_contents):
-    db = self.db()
-    self.files['/foo/OWNERS'] = owners_file_contents
-    self.files['/foo/DEPS'] = ''
-    try:
-      db.reviewers_for(['foo/DEPS'])
-      self.fail()  # pragma: no cover
-    except owners.SyntaxErrorInOwnersFile, e:
-      self.assertTrue(str(e).startswith('/foo/OWNERS:1'))
-
-  def test_syntax_error__unknown_token(self):
-    self.assert_syntax_error('{}\n')
-
-  def test_syntax_error__unknown_set(self):
-    self.assert_syntax_error('set myfatherisbillgates\n')
-
-  def test_syntax_error__bad_email(self):
-    self.assert_syntax_error('ben\n')
+    self.assert_reviewers_for(['content/baz/OWNERS'],
+                              [john],
+                              [darin])
 
+  def test_reviewers_for__per_file(self):
+    self.files['/content/baz/OWNERS'] = owners_file(lines=[
+        'per-file ugly.*=tom@example.com'])
+    self.assert_reviewers_for(['content/baz/ugly.cc'],
+                              [tom])
+
+  def test_reviewers_for__two_nested_dirs(self):
+    # The same owner is listed in two directories (one above the other)
+    self.assert_reviewers_for(['chrome/browser/defaults.h'],
+                              [brett])
+
+class LowestCostOwnersTest(_BaseTestCase):
+  # Keep the data in the test_lowest_cost_owner* methods as consistent with
+  # test_repo() where possible to minimize confusion.
+
+  def check(self, possible_owners, dirs, *possible_lowest_cost_owners):
+    suggested_owner = owners.Database.lowest_cost_owner(possible_owners, dirs)
+    self.assertTrue(suggested_owner in possible_lowest_cost_owners)
+
+  def test_one_dir_with_owner(self):
+    # brett is the only immediate owner for stuff in baz; john is also
+    # an owner, but further removed. We should always get brett.
+    self.check({brett: [('content/baz', 1)],
+                john:  [('content/baz', 2)]},
+               ['content/baz'],
+               brett)
+
+    # john and darin are owners for content; the suggestion could be either.
+  def test_one_dir_with_two_owners(self):
+    self.check({john:  [('content', 1)],
+                darin: [('content', 1)]},
+               ['content'],
+               john, darin)
+
+  def test_one_dir_with_two_owners_in_parent(self):
+    # As long as the distance is the same, it shouldn't matter (brett isn't
+    # listed in this case).
+    self.check({john:  [('content/baz', 2)],
+                darin: [('content/baz', 2)]},
+               ['content/baz'],
+               john, darin)
+
+  def test_two_dirs_two_owners(self):
+    # If they both match both dirs, they should be treated equally.
+    self.check({john:  [('content/baz', 2), ('content/bar', 2)],
+                darin: [('content/baz', 2), ('content/bar', 2)]},
+               ['content/baz', 'content/bar'],
+               john, darin)
+
+    # Here brett is better since he's closer for one of the two dirs.
+    self.check({brett: [('content/baz', 1), ('content/views', 1)],
+                darin: [('content/baz', 2), ('content/views', 1)]},
+               ['content/baz', 'content/views'],
+               brett)
+
+  def test_hierarchy(self):
+    # the choices in these tests are more arbitrary value judgements;
+    # also, here we drift away from test_repo() to cover more cases.
+
+    # Here ben isn't picked, even though he can review both; we prefer
+    # closer reviewers.
+    self.check({ben: [('chrome/gpu', 2), ('chrome/renderer', 2)],
+                ken: [('chrome/gpu', 1)],
+                peter: [('chrome/renderer', 1)]},
+               ['chrome/gpu', 'chrome/renderer'],
+               ken, peter)
+
+    # Here we always pick ben since he can review either dir as well as
+    # the others but can review both (giving us fewer total reviewers).
+    self.check({ben: [('chrome/gpu', 1), ('chrome/renderer', 1)],
+                ken: [('chrome/gpu', 1)],
+                peter: [('chrome/renderer', 1)]},
+               ['chrome/gpu', 'chrome/renderer'],
+               ben)
+
+    # However, three reviewers is too many, so ben gets this one.
+    self.check({ben: [('chrome/gpu', 2), ('chrome/renderer', 2),
+                      ('chrome/browser', 2)],
+                ken: [('chrome/gpu', 1)],
+                peter: [('chrome/renderer', 1)],
+                brett: [('chrome/browser', 1)]},
+               ['chrome/gpu', 'chrome/renderer',
+                'chrome/browser'],
+               ben)
 
 if __name__ == '__main__':
   unittest.main()