[presubmit] Add check to prevent new metadata in OWNERS files.

Bug: 1113033
Change-Id: I000cd307fea8862b9ef9cab907aafd357ee761bc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2582566
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>
Auto-Submit: Edward Lesmes <ehmaldonado@chromium.org>
Reviewed-by: Josip Sokcevic <sokcevic@google.com>

presubmit_canned_checks.py

@@ -1069,6 +1069,33 @@ def CheckDirMetadataFormat(input_api, output_api, dirmd_bin=None):
       name, cmd, kwargs, output_api.PresubmitError)]
 
 
+def CheckNoNewMetadataInOwners(input_api, output_api):
+  """Check that no metadata is added to OWNERS files."""
+  _METADATA_LINE_RE = input_api.re.compile(
+      r'^#\s*(TEAM|COMPONENT|OS|WPT-NOTIFY)+\s*:\s*\S+$',
+      input_api.re.MULTILINE | input_api.re.IGNORECASE)
+  affected_files = input_api.change.AffectedFiles(
+      include_deletes=False,
+      file_filter=lambda f: input_api.basename(f.LocalPath()) == 'OWNERS')
+
+  errors = []
+  for f in affected_files:
+    for _, line in f.ChangedContents():
+      if _METADATA_LINE_RE.search(line):
+        errors.append(f.AbsoluteLocalPath())
+        break
+
+  if not errors:
+    return []
+
+  return [output_api.PresubmitError(
+      'New metadata was added to the following OWNERS files, but should '
+      'have been added to DIR_METADATA files instead:\n' +
+      '\n'.join(errors) + '\n' +
+      'See https://source.chromium.org/chromium/infra/infra/+/HEAD:'
+      'go/src/infra/tools/dirmd/proto/dir_metadata.proto for details.')]
+
+
 def CheckOwnersDirMetadataExclusive(input_api, output_api):
   """Check that metadata in OWNERS files and DIR_METADATA files are mutually
   exclusive.

tests/presubmit_unittest.py

@@ -2572,11 +2572,14 @@ the current line as well!
     change.AffectedFiles = lambda *a, **kw: (
         presubmit.Change.AffectedFiles(change, *a, **kw))
     change._affected_files = []
-    for path, (action, _) in files.items():
+    for path, (action, contents) in files.items():
       affected_file = mock.MagicMock(presubmit.GitAffectedFile)
       affected_file.AbsoluteLocalPath.return_value = path
       affected_file.LocalPath.return_value = path
       affected_file.Action.return_value = action
+      affected_file.ChangedContents.return_value = [
+         (1, contents or ''),
+      ]
       change._affected_files.append(affected_file)
 
     input_api = self.MockInputApi(None, False)
@@ -2608,6 +2611,26 @@ the current line as well!
     self.assertEqual(1, len(commands))
     self.assertEqual(expected_cmd, commands[0].cmd)
 
+  def testCheckNoNewMetadataInOwners(self):
+    input_api = self.GetInputApiWithFiles({
+        'no-new-metadata/OWNERS': ('M', '# WARNING: Blah'),
+        'added-no-new-metadata/OWNERS': ('A', '# WARNING: Bleh'),
+        'deleted/OWNERS': ('D', None),
+    })
+    self.assertEqual(
+        [],
+        presubmit_canned_checks.CheckNoNewMetadataInOwners(
+            input_api, presubmit.OutputApi))
+
+  def testCheckNoNewMetadataInOwnersFails(self):
+    input_api = self.GetInputApiWithFiles({
+        'new-metadata/OWNERS': ('M', '# CoMpOnEnT: Monorail>Component'),
+    })
+    results = presubmit_canned_checks.CheckNoNewMetadataInOwners(
+        input_api, presubmit.OutputApi)
+    self.assertEqual(1, len(results))
+    self.assertIsInstance(results[0], presubmit.OutputApi.PresubmitError)
+
   def testCheckOwnersDirMetadataExclusiveWorks(self):
     input_api = self.GetInputApiWithFiles({
         'only-owners/OWNERS': ('M', '# COMPONENT: Monorail>Component'),