Rework the owner-suggesting algorithm.

tests/owners_unittest.py

Index: tests/owners_unittest.py
diff --git a/tests/owners_unittest.py b/tests/owners_unittest.py
index 34272a1337da077c57ab3ff285f7e219b4ab572b..462386d9a85319a82bdb4ac9095c4b4b0facf781 100755
--- a/tests/owners_unittest.py
+++ b/tests/owners_unittest.py
@@ -58,7 +58,7 @@ 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 +73,8 @@ 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 +207,41 @@ 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 +263,16 @@ 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 +282,96 @@ 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])
+
+
+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()