Optimize presubmit --all with --no_diffs option

Some of the expensive checks when running presubmit --all, such as
CheckStableMojomChanges (~300 s) and CheckAddedDepsHaveTargetApprovals
(~200 s) only look at diffs and are therefore guaranteed to be NOPs when
running presubmit --all or --files=. Passing along the no_diffs state
lets these expensive checks be skipped, thus allowing for faster
iteration times.

Initial testing suggests that (with some supporting changes in the
Chromium repo) this reduces "presubmit --all" times by about ten
minutes, or a bit more than 10%, and additional improvements may be
possible.

Special handling for the no-diffs case also offers a simple way to avoid
presubmit failures that happen whenever all files are flagged as being
changed.

Finally, and perhaps most importantly for having a presubmit --all bot,
when --no_diffs is passed we can treat errors like "Issue wasn't
uploaded" and "Add a description to the CL" as messages, thus making it
possible to have zero presubmit errors when run on origin/main.

Bug: 1320937, 1322936
Change-Id: I0d09dd4aae8fdaa48c8b2f89337441cf96dcff72
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3628368
Commit-Queue: Bruce Dawson <brucedawson@chromium.org>
Reviewed-by: Gavin Mak <gavinmak@google.com>

git_cl.py

@@ -1362,6 +1362,8 @@ class Changelist(object):
     if files:
       args.extend(files.split(';'))
       args.append('--source_controlled_only')
+    if files or all_files:
+      args.append('--no_diffs')
 
     if resultdb and not realm:
       # TODO (crbug.com/1113463): store realm somewhere and look it up so

presubmit_canned_checks.py

@@ -111,7 +111,7 @@ def CheckChangeHasDescription(input_api, output_api):
   """Checks the CL description is not empty."""
   text = input_api.change.DescriptionText()
   if text.strip() == '':
-    if input_api.is_committing:
+    if input_api.is_committing and not input_api.no_diffs:
       return [output_api.PresubmitError('Add a description to the CL.')]
 
     return [output_api.PresubmitNotifyResult('Add a description to the CL.')]
@@ -121,8 +121,11 @@ def CheckChangeHasDescription(input_api, output_api):
 def CheckChangeWasUploaded(input_api, output_api):
   """Checks that the issue was uploaded before committing."""
   if input_api.is_committing and not input_api.change.issue:
-    return [output_api.PresubmitError(
-      'Issue wasn\'t uploaded. Please upload first.')]
+    message = 'Issue wasn\'t uploaded. Please upload first.'
+    if input_api.no_diffs:
+      # Make this just a message with presubmit --all and --files
+      return [output_api.PresubmitNotifyResult(message)]
+    return [output_api.PresubmitError(message)]
   return []
 
 
@@ -326,6 +329,9 @@ def CheckGenderNeutral(input_api, output_api, source_file_filter=None):
   """Checks that there are no gendered pronouns in any of the text files to be
   submitted.
   """
+  if input_api.no_diffs:
+    return []
+
   gendered_re = input_api.re.compile(
       r'(^|\s|\(|\[)([Hh]e|[Hh]is|[Hh]ers?|[Hh]im|[Ss]he|[Gg]uys?)\\b')
 
@@ -419,6 +425,8 @@ def _FindNewViolationsOfRule(callable_rule,
   Returns:
     A list of the newly-introduced violations reported by the rule.
   """
+  if input_api.no_diffs:
+    return []
   return _FindNewViolationsOfRuleForList(
       callable_rule, _GenerateAffectedFileExtList(
           input_api, source_file_filter), error_formatter)
@@ -475,6 +483,8 @@ def CheckLongLines(input_api, output_api, maxlen, source_file_filter=None):
   """Checks that there aren't any lines longer than maxlen characters in any of
   the text files to be submitted.
   """
+  if input_api.no_diffs:
+    return []
   maxlens = {
       'java': 100,
       # This is specifically for Android's handwritten makefiles (Android.mk).
@@ -1165,6 +1175,9 @@ def CheckDirMetadataFormat(input_api, output_api, dirmd_bin=None):
 
 def CheckNoNewMetadataInOwners(input_api, output_api):
   """Check that no metadata is added to OWNERS files."""
+  if input_api.no_diffs:
+    return []
+
   _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)
@@ -1938,6 +1951,8 @@ def CheckInclusiveLanguage(input_api, output_api,
   # chromium/src.
   if input_api.change.RepositoryRoot() != input_api.PresubmitLocalPath():
     return []
+  if input_api.no_diffs:
+    return []
 
   warnings = []
   errors = []

presubmit_support.py

@@ -590,7 +590,8 @@ class InputApi(object):
   )
 
   def __init__(self, change, presubmit_path, is_committing,
-      verbose, gerrit_obj, dry_run=None, thread_pool=None, parallel=False):
+      verbose, gerrit_obj, dry_run=None, thread_pool=None, parallel=False,
+      no_diffs=False):
     """Builds an InputApi object.
 
     Args:
@@ -601,6 +602,8 @@ class InputApi(object):
       dry_run: if true, some Checks will be skipped.
       parallel: if true, all tests reported via input_api.RunTests for all
                 PRESUBMIT files will be run in parallel.
+      no_diffs: if true, implies that --files or --all was specified so some
+                checks can be skipped, and some errors will be messages.
     """
     # Version number of the presubmit_support script.
     self.version = [int(x) for x in __version__.split('.')]
@@ -608,6 +611,7 @@ class InputApi(object):
     self.is_committing = is_committing
     self.gerrit = gerrit_obj
     self.dry_run = dry_run
+    self.no_diffs = no_diffs
 
     self.parallel = parallel
     self.thread_pool = thread_pool or ThreadPool()
@@ -1493,7 +1497,8 @@ def DoPostUploadExecuter(change, gerrit_obj, verbose, use_python3=False):
 
 class PresubmitExecuter(object):
   def __init__(self, change, committing, verbose, gerrit_obj, dry_run=None,
-               thread_pool=None, parallel=False, use_python3=False):
+               thread_pool=None, parallel=False, use_python3=False,
+               no_diffs=False):
     """
     Args:
       change: The Change object.
@@ -1504,6 +1509,8 @@ class PresubmitExecuter(object):
                 PRESUBMIT files will be run in parallel.
       use_python3: if true, will use python3 instead of python2 by default
                 if USE_PYTHON3 is not specified.
+      no_diffs: if true, implies that --files or --all was specified so some
+                checks can be skipped, and some errors will be messages.
     """
     self.change = change
     self.committing = committing
@@ -1514,6 +1521,7 @@ class PresubmitExecuter(object):
     self.thread_pool = thread_pool
     self.parallel = parallel
     self.use_python3 = use_python3
+    self.no_diffs = no_diffs
 
   def ExecPresubmitScript(self, script_text, presubmit_path):
     """Executes a single presubmit script.
@@ -1537,7 +1545,7 @@ class PresubmitExecuter(object):
     input_api = InputApi(self.change, presubmit_path, self.committing,
                          self.verbose, gerrit_obj=self.gerrit,
                          dry_run=self.dry_run, thread_pool=self.thread_pool,
-                         parallel=self.parallel)
+                         parallel=self.parallel, no_diffs=self.no_diffs)
     output_api = OutputApi(self.committing)
     context = {}
 
@@ -1671,7 +1679,8 @@ def DoPresubmitChecks(change,
                       dry_run=None,
                       parallel=False,
                       json_output=None,
-                      use_python3=False):
+                      use_python3=False,
+                      no_diffs=False):
   """Runs all presubmit checks that apply to the files in the change.
 
   This finds all PRESUBMIT.py files in directories enclosing the files in the
@@ -1694,6 +1703,8 @@ def DoPresubmitChecks(change,
               PRESUBMIT files will be run in parallel.
     use_python3: if true, default to using Python3 for presubmit checks
                  rather than Python2.
+    no_diffs: if true, implies that --files or --all was specified so some
+              checks can be skipped, and some errors will be messages.
   Return:
     1 if presubmit checks failed or 0 otherwise.
   """
@@ -1718,7 +1729,8 @@ def DoPresubmitChecks(change,
     results = []
     thread_pool = ThreadPool()
     executer = PresubmitExecuter(change, committing, verbose, gerrit_obj,
-                                 dry_run, thread_pool, parallel, use_python3)
+                                 dry_run, thread_pool, parallel, use_python3,
+                                 no_diffs)
     skipped_count = 0;
     if default_presubmit:
       if verbose:
@@ -1989,6 +2001,7 @@ def main(argv=None):
                       help='Write presubmit errors to json output.')
   parser.add_argument('--all_files', action='store_true',
                       help='Mark all files under source control as modified.')
+
   parser.add_argument('files', nargs='*',
                       help='List of files to be marked as modified when '
                       'executing presubmit or post-upload hooks. fnmatch '
@@ -1997,6 +2010,8 @@ def main(argv=None):
                       help='Constrain \'files\' to those in source control.')
   parser.add_argument('--use-python3', action='store_true',
                       help='Use python3 for presubmit checks by default')
+  parser.add_argument('--no_diffs', action='store_true',
+                      help='Assume that all "modified" files have no diffs.')
   options = parser.parse_args(argv)
 
   log_level = logging.ERROR
@@ -2028,7 +2043,8 @@ def main(argv=None):
           options.dry_run,
           options.parallel,
           options.json_output,
-          options.use_python3)
+          options.use_python3,
+          options.no_diffs)
   except PresubmitFailure as e:
     import utils
     print(e, file=sys.stderr)

tests/git_cl_test.py

@@ -3109,6 +3109,7 @@ class ChangelistTest(unittest.TestCase):
         '--may_prompt',
         '--parallel',
         '--all_files',
+        '--no_diffs',
         '--json_output', '/tmp/fake-temp2',
         '--description_file', '/tmp/fake-temp1',
     ])
@@ -3127,6 +3128,7 @@ class ChangelistTest(unittest.TestCase):
         '--may_prompt',
         '--parallel',
         '--all_files',
+        '--no_diffs',
         '--json_output', '/tmp/fake-temp4',
         '--description_file', '/tmp/fake-temp3',
     ])

tests/presubmit_unittest.py

@@ -1791,6 +1791,7 @@ class CannedChecksUnittest(PresubmitTestsBase):
     input_api.subprocess.CalledProcessError = fake_CalledProcessError
     input_api.verbose = False
     input_api.is_windows = False
+    input_api.no_diffs = False
 
     input_api.change = change
     input_api.is_committing = committing