llvm_tools: add a nightly revert checker

This CL adds a script that uses our new revert checker bits to send
nightly emails about newly-discovered reverts in LLVM. It should be
directly usable from a crontab.

BUG=chromium:1046988
TEST=unittests; a few dry-run emails

Change-Id: I361d3e214c5d563e71cc4120b76b78e5b3e63f40
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/2165514
Reviewed-by: Tiancong Wang <tcwang@google.com>
Tested-by: George Burgess <gbiv@chromium.org>

1 files changed, 215 insertions, 0 deletions

diff --git a/llvm_tools/nightly_revert_checker.py b/llvm_tools/nightly_revert_checker.py
new file mode 100755
index 00000000..b7b87fad
--- /dev/null
+++ b/llvm_tools/nightly_revert_checker.py
@@ -0,0 +1,215 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+# Copyright 2020 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""Checks for new reverts in LLVM on a nightly basis.
+
+If any reverts are found that were previously unknown, this fires off an email.
+All LLVM SHAs to monitor are autodetected.
+"""
+
+# pylint: disable=cros-logging-import
+
+from __future__ import print_function
+
+import argparse
+import io
+import json
+import logging
+import os
+import pprint
+import sys
+import typing as t
+
+import cros_utils.email_sender as email_sender
+import revert_checker
+
+State = t.Any
+
+# FIXME(gbiv): we probably want to have Android compat here, too. Should be
+# easy to nab their testing version automatically with:
+# git merge-base m/llvm-toolchain aosp/upstream-master
+
+
+def _parse_llvm_ebuild_for_shas(
+    ebuild_file: io.TextIOWrapper) -> t.List[t.Tuple[str]]:
+
+  def parse_ebuild_assignment(line: str) -> str:
+    no_comments = line.split('#')[0]
+    no_assign = no_comments.split('=', 1)[1].strip()
+    assert no_assign.startswith('"') and no_assign.endswith('"'), no_assign
+    return no_assign[1:-1]
+
+  llvm_hash, llvm_next_hash = None, None
+  for line in ebuild_file:
+    if line.startswith('LLVM_HASH='):
+      llvm_hash = parse_ebuild_assignment(line)
+      if llvm_next_hash:
+        break
+    if line.startswith('LLVM_NEXT_HASH'):
+      llvm_next_hash = parse_ebuild_assignment(line)
+      if llvm_hash:
+        break
+  if not llvm_next_hash or not llvm_hash:
+    raise ValueError('Failed to detect SHAs for llvm/llvm_next. Got: '
+                     'llvm=%s; llvm_next=%s' % (llvm_hash, llvm_next_hash))
+  return [('llvm', llvm_hash), ('llvm-next', llvm_next_hash)]
+
+
+def _find_interesting_shas(chromeos_base: str) -> t.List[t.Tuple[str]]:
+  llvm_dir = os.path.join(chromeos_base,
+                          'src/third_party/chromiumos-overlay/sys-devel/llvm')
+  candidate_ebuilds = [
+      os.path.join(llvm_dir, x)
+      for x in os.listdir(llvm_dir)
+      if '_pre' in x and not os.path.islink(os.path.join(llvm_dir, x))
+  ]
+
+  if len(candidate_ebuilds) != 1:
+    raise ValueError('Expected exactly one llvm ebuild candidate; got %s' %
+                     pprint.pformat(candidate_ebuilds))
+
+  with open(candidate_ebuilds[0], encoding='utf-8') as f:
+    return _parse_llvm_ebuild_for_shas(f)
+
+
+_Email = t.NamedTuple('_Email', [
+    ('subject', str),
+    ('body', str),
+])
+
+
+def _generate_revert_email(
+    friendly_name: str, sha: str,
+    new_reverts: t.List[revert_checker.Revert]) -> _Email:
+  email_lines = [
+      'It looks like there may be %s across %s (%s).' % (
+          'a new revert' if len(new_reverts) == 1 else 'new reverts',
+          friendly_name,
+          sha,
+      ),
+      '',
+      'That is:' if len(new_reverts) == 1 else 'These are:',
+  ]
+
+  for revert in sorted(new_reverts, key=lambda r: r.sha):
+    email_lines.append(
+        '\t- %s (appears to revert %s)' % (revert.sha, revert.reverted_sha))
+
+  email_lines.append('')
+  email_lines.append('PTAL and consider reverting them locally.')
+  return _Email(
+      subject='[revert-checker] new %s discovered across %s' % (
+          'revert' if len(new_reverts) == 1 else 'reverts',
+          friendly_name,
+      ),
+      body='\n'.join(email_lines),
+  )
+
+
+def _send_revert_email(email: _Email) -> None:
+  email_sender.EmailSender().SendX20Email(
+      subject=email.subject,
+      identifier='revert-checker',
+      well_known_recipients=['mage'],
+      direct_recipients=['gbiv@google.com'],
+      text_body=email.body)
+
+
+def _write_state(state_file: str, new_state: State) -> None:
+  try:
+    tmp_file = state_file + '.new'
+    with open(tmp_file, 'w', encoding='utf-8') as f:
+      json.dump(new_state, f, sort_keys=True, indent=2, separators=(',', ': '))
+    os.rename(tmp_file, state_file)
+  except:
+    try:
+      os.remove(tmp_file)
+    except FileNotFoundError:
+      pass
+    raise
+
+
+def _read_state(state_file: str) -> State:
+  try:
+    with open(state_file) as f:
+      return json.load(f)
+  except FileNotFoundError:
+    logging.info('No state file found at %r; starting with an empty slate',
+                 state_file)
+    return {}
+
+
+def main(argv: t.List[str]) -> None:
+  parser = argparse.ArgumentParser(
+      description=__doc__, formatter_class=argparse.RawDescriptionHelpFormatter)
+  parser.add_argument(
+      '--state_file', required=True, help='File to store persistent state in.')
+  parser.add_argument(
+      '--llvm_dir', required=True, help='Up-to-date LLVM directory to use.')
+  parser.add_argument(
+      '--chromeos_dir', required=True, help='Up-to-date CrOS directory to use.')
+  parser.add_argument(
+      '--dry_run',
+      action='store_true',
+      help='Print email contents, rather than sending them.')
+  parser.add_argument('--debug', action='store_true')
+  opts = parser.parse_args(argv)
+
+  logging.basicConfig(
+      format='%(asctime)s: %(levelname)s: %(filename)s:%(lineno)d: %(message)s',
+      level=logging.DEBUG if opts.debug else logging.INFO,
+  )
+
+  state_file = opts.state_file
+  dry_run = opts.dry_run
+
+  state = _read_state(state_file)
+
+  interesting_shas = _find_interesting_shas(opts.chromeos_dir)
+  logging.info('Interesting SHAs were %r', interesting_shas)
+
+  new_state: State = {}
+  revert_emails_to_send: t.List[t.Tuple[str, t.List[revert_checker
+                                                    .Revert]]] = []
+  for friendly_name, sha in interesting_shas:
+    logging.info('Finding reverts across %s (%s)', friendly_name, sha)
+    all_reverts = revert_checker.find_reverts(
+        opts.llvm_dir, sha, root='origin/master')
+    logging.info('Detected the following revert(s) across %s:\n%s',
+                 friendly_name, pprint.pformat(all_reverts))
+
+    new_state[sha] = [r.sha for r in all_reverts]
+
+    if sha not in state:
+      logging.info('SHA %s is new to me', sha)
+      existing_reverts = set()
+    else:
+      existing_reverts = set(state[sha])
+
+    new_reverts = [r for r in all_reverts if r.sha not in existing_reverts]
+    if not new_reverts:
+      logging.info('...All of which have been reported.')
+      continue
+
+    revert_emails_to_send.append(
+        _generate_revert_email(friendly_name, sha, new_reverts))
+
+  # We want to be as free of obvious side-effects as possible in case something
+  # above breaks. Hence, send the email as late as possible.
+  for email in revert_emails_to_send:
+    if dry_run:
+      logging.info('Would send email:\nSubject: %s\nBody:\n%s\n', email.subject,
+                   email.body)
+    else:
+      logging.info('Sending email with subject %r...', email.subject)
+      _send_revert_email(email)
+      logging.info('Email sent.')
+
+  _write_state(state_file, new_state)
+
+
+if __name__ == '__main__':
+  sys.exit(main(sys.argv[1:]))