Add a yapf style to //build/chromeos/ and auto-format all python files.

Format all the things!

Change-Id: I33f02e6e21c4388f381b35e06394fb916bfddddd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1891735
Commit-Queue: Ben Pastene <bpastene@chromium.org>
Reviewed-by: John Budorick <jbudorick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#711845}

build/chromeos/.style.yapf

+[style]
+based_on_style = chromium

build/chromeos/PRESUBMIT.py

 # Copyright (c) 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
-
 """Presubmit script for build/chromeos/.
 
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts for
@@ -11,9 +10,7 @@ details on the presubmit API built into depot_tools.
 
 def CommonChecks(input_api, output_api):
   return input_api.canned_checks.RunPylint(
-      input_api,
-      output_api,
-      pylintrc='pylintrc')
+      input_api, output_api, pylintrc='pylintrc')
 
 
 def CheckChangeOnUpload(input_api, output_api):

build/chromeos/create_test_runner_script.py

@@ -3,7 +3,6 @@
 # Copyright 2018 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
-
 """Creates a script that runs a CrOS VM test by delegating to
 build/chromeos/test_runner.py.
 """
@@ -12,7 +11,6 @@ import argparse
 import os
 import sys
 
-
 SCRIPT_TEMPLATE = """\
 #!/usr/bin/env python
 #
@@ -90,7 +88,8 @@ def main(args):
       vm_test_args.append('--deploy-chrome')
 
   vm_test_args += [
-      '--board', args.board,
+      '--board',
+      args.board,
       '-v',
   ]
   if args.use_vm:
@@ -100,17 +99,18 @@ def main(args):
       ('--cros-cache', RelativizePathToScript(args.cros_cache)),
   ]
   if args.runtime_deps_path:
-    vm_test_path_args.append(
-        ('--runtime-deps-path', RelativizePathToScript(args.runtime_deps_path)))
+    vm_test_path_args.append(('--runtime-deps-path',
+                              RelativizePathToScript(args.runtime_deps_path)))
   if args.output_directory:
-    vm_test_path_args.append(
-        ('--path-to-outdir', RelativizePathToScript(args.output_directory)))
+    vm_test_path_args.append(('--path-to-outdir',
+                              RelativizePathToScript(args.output_directory)))
 
   with open(args.script_output_path, 'w') as script:
-    script.write(SCRIPT_TEMPLATE.format(
-        vm_test_script=run_test_path,
-        vm_test_args=str(vm_test_args),
-        vm_test_path_args=str(vm_test_path_args)))
+    script.write(
+        SCRIPT_TEMPLATE.format(
+            vm_test_script=run_test_path,
+            vm_test_args=str(vm_test_args),
+            vm_test_path_args=str(vm_test_path_args)))
 
   os.chmod(args.script_output_path, 0750)
 

build/chromeos/test_runner.py

@@ -22,8 +22,8 @@ import dateutil.parser  # pylint: disable=import-error
 import jsonlines  # pylint: disable=import-error
 import psutil  # pylint: disable=import-error
 
-CHROMIUM_SRC_PATH = os.path.abspath(os.path.join(
-    os.path.dirname(__file__), '..', '..'))
+CHROMIUM_SRC_PATH = os.path.abspath(
+    os.path.join(os.path.dirname(__file__), '..', '..'))
 
 # Use the android test-runner's gtest results support library for generating
 # output json ourselves.
@@ -36,12 +36,12 @@ sys.path.insert(
     0, os.path.join(CHROMIUM_SRC_PATH, 'tools', 'swarming_client', 'utils'))
 import subprocess42  # pylint: disable=import-error
 
-DEFAULT_CROS_CACHE = os.path.abspath(os.path.join(
-    CHROMIUM_SRC_PATH, 'build', 'cros_cache'))
-CHROMITE_PATH = os.path.abspath(os.path.join(
-    CHROMIUM_SRC_PATH, 'third_party', 'chromite'))
-CROS_RUN_TEST_PATH = os.path.abspath(os.path.join(
-    CHROMITE_PATH, 'bin', 'cros_run_test'))
+DEFAULT_CROS_CACHE = os.path.abspath(
+    os.path.join(CHROMIUM_SRC_PATH, 'build', 'cros_cache'))
+CHROMITE_PATH = os.path.abspath(
+    os.path.join(CHROMIUM_SRC_PATH, 'third_party', 'chromite'))
+CROS_RUN_TEST_PATH = os.path.abspath(
+    os.path.join(CHROMITE_PATH, 'bin', 'cros_run_test'))
 
 # GN target that corresponds to the cros browser sanity test.
 SANITY_TEST_TARGET = 'cros_browser_sanity_test'
@@ -68,15 +68,15 @@ class RemoteTest(object):
   # This is a basic shell script that can be appended to in order to invoke the
   # test on the device.
   BASIC_SHELL_SCRIPT = [
-    '#!/bin/sh',
-
-    # /home and /tmp are mounted with "noexec" in the device, but some of our
-    # tools and tests use those dirs as a workspace (eg: vpython downloads
-    # python binaries to ~/.vpython-root and /tmp/vpython_bootstrap).
-    # /usr/local/tmp doesn't have this restriction, so change the location of
-    # the home and temp dirs for the duration of the test.
-    'export HOME=/usr/local/tmp',
-    'export TMPDIR=/usr/local/tmp',
+      '#!/bin/sh',
+
+      # /home and /tmp are mounted with "noexec" in the device, but some of our
+      # tools and tests use those dirs as a workspace (eg: vpython downloads
+      # python binaries to ~/.vpython-root and /tmp/vpython_bootstrap).
+      # /usr/local/tmp doesn't have this restriction, so change the location of
+      # the home and temp dirs for the duration of the test.
+      'export HOME=/usr/local/tmp',
+      'export TMPDIR=/usr/local/tmp',
   ]
 
   def __init__(self, args, unknown_args):
@@ -96,15 +96,18 @@ class RemoteTest(object):
 
     self._test_cmd = [
         CROS_RUN_TEST_PATH,
-        '--board', args.board,
-        '--cache-dir', args.cros_cache,
+        '--board',
+        args.board,
+        '--cache-dir',
+        args.cros_cache,
     ]
     if args.use_vm:
       self._test_cmd += [
           '--start',
           # Don't persist any filesystem changes after the VM shutsdown.
           '--copy-on-write',
-          '--device', 'localhost'
+          '--device',
+          'localhost'
       ]
     else:
       self._test_cmd += [
@@ -127,9 +130,7 @@ class RemoteTest(object):
       self._llvm_profile_var = '/tmp/profraw/%s' % llvm_profile_file
 
       # This should make the vm test runner exfil the profiling data.
-      self._test_cmd += [
-          '--results-src', '/tmp/profraw'
-      ]
+      self._test_cmd += ['--results-src', '/tmp/profraw']
 
     self._test_env = setup_env()
 
@@ -146,7 +147,8 @@ class RemoteTest(object):
     # set cwd.
     self._test_cmd += [
         '--remote-cmd',
-        '--cwd', os.path.relpath(self._path_to_outdir, CHROMIUM_SRC_PATH),
+        '--cwd',
+        os.path.relpath(self._path_to_outdir, CHROMIUM_SRC_PATH),
     ]
     logging.info('Running the following command on the device:')
     logging.info('\n' + '\n'.join(script_contents))
@@ -162,10 +164,10 @@ class RemoteTest(object):
     # and gets timeout-killed by swarming. See also:
     # https://chromium.googlesource.com/infra/luci/luci-py/+/master/appengine/swarming/doc/Bot.md#graceful-termination_aka-the-sigterm-and-sigkill-dance
     test_proc = None
+
     def _kill_child_procs(trapped_signal, _):
-      logging.warning(
-          'Received signal %d. Killing child processes of test.',
-          trapped_signal)
+      logging.warning('Received signal %d. Killing child processes of test.',
+                      trapped_signal)
       if not test_proc or not test_proc.pid:
         # This shouldn't happen?
         logging.error('Test process not running.')
@@ -176,12 +178,14 @@ class RemoteTest(object):
 
     signal.signal(signal.SIGTERM, _kill_child_procs)
 
-    for i in xrange(self._retries+1):
+    for i in xrange(self._retries + 1):
       logging.info('########################################')
       logging.info('Test attempt #%d', i)
       logging.info('########################################')
       test_proc = subprocess42.Popen(
-          self._test_cmd, stdout=sys.stdout, stderr=sys.stderr,
+          self._test_cmd,
+          stdout=sys.stdout,
+          stderr=sys.stderr,
           env=self._test_env)
       try:
         test_proc.wait(timeout=self._timeout)
@@ -214,8 +218,9 @@ class RemoteTest(object):
     # only one test (suite_name), and will either be a PASS or FAIL depending on
     # return_code.
     if self._test_launcher_summary_output:
-      result = (base_test_result.ResultType.FAIL if return_code else
-                    base_test_result.ResultType.PASS)
+      result = (
+          base_test_result.ResultType.FAIL
+          if return_code else base_test_result.ResultType.PASS)
       suite_result = base_test_result.BaseTestResult(self.suite_name, result)
       run_results = base_test_result.TestRunResults()
       run_results.AddResult(suite_result)
@@ -245,17 +250,17 @@ class TastTest(RemoteTest):
 
   def build_test_command(self):
     if '--gtest_filter=%s' % self.suite_name in self._additional_args:
-      logging.info(
-          'GTest filtering not supported for tast tests. The '
-          '--gtest_filter arg will be ignored.')
+      logging.info('GTest filtering not supported for tast tests. The '
+                   '--gtest_filter arg will be ignored.')
       self._additional_args.remove('--gtest_filter=%s' % self.suite_name)
     if any(arg.startswith('--gtest_repeat') for arg in self._additional_args):
       logging.info(
           '--gtest_repeat not supported for tast tests. The arg will be '
           'ignored.')
       self._additional_args = [
-          arg for arg in self._additional_args if not arg.startswith(
-              '--gtest_repeat')]
+          arg for arg in self._additional_args
+          if not arg.startswith('--gtest_repeat')
+      ]
 
     if self._additional_args:
       logging.error(
@@ -265,7 +270,8 @@ class TastTest(RemoteTest):
     self._test_cmd += [
         '--deploy',
         '--mount',
-        '--build-dir', os.path.relpath(self._path_to_outdir, CHROMIUM_SRC_PATH),
+        '--build-dir',
+        os.path.relpath(self._path_to_outdir, CHROMIUM_SRC_PATH),
     ]
 
     # Coverage tests require some special pre-test setup, so use an
@@ -276,8 +282,8 @@ class TastTest(RemoteTest):
       # test.
       device_test_script_contents = self.BASIC_SHELL_SCRIPT[:]
       device_test_script_contents += [
-          'echo "LLVM_PROFILE_FILE=%s" >> /etc/chrome_dev.conf' % (
-              self._llvm_profile_var)
+          'echo "LLVM_PROFILE_FILE=%s" >> /etc/chrome_dev.conf' %
+          (self._llvm_profile_var)
       ]
 
       local_test_runner_cmd = ['local_test_runner', '-waituntilready']
@@ -295,8 +301,8 @@ class TastTest(RemoteTest):
           device_test_script_contents)
 
       self._test_cmd += [
-          '--files', os.path.relpath(self._on_device_script),
-          '--',
+          '--files',
+          os.path.relpath(self._on_device_script), '--',
           './' + os.path.relpath(self._on_device_script, self._path_to_outdir)
       ]
     else:
@@ -306,7 +312,8 @@ class TastTest(RemoteTest):
       # Capture tast's results in the logs dir as well.
       if self._logs_dir:
         self._test_cmd += [
-            '--results-dir', self._logs_dir,
+            '--results-dir',
+            self._logs_dir,
         ]
       if self._conditional:
         # Don't use pipes.quote() here. Something funky happens with the arg
@@ -327,8 +334,8 @@ class TastTest(RemoteTest):
     tast_results_path = os.path.join(self._logs_dir, 'streamed_results.jsonl')
     if not os.path.exists(tast_results_path):
       logging.error(
-         'Tast results not found at %s. Falling back to generic result '
-         'reporting.', tast_results_path)
+          'Tast results not found at %s. Falling back to generic result '
+          'reporting.', tast_results_path)
       return super(TastTest, self).post_run(return_code)
 
     # See the link below for the format of the results:
@@ -357,8 +364,8 @@ class TastTest(RemoteTest):
         for err in errors:
           error_log += err['stack'].encode('utf-8') + '\n'
       error_log += (
-           "\nIf you're unsure why this test failed, consult the steps "
-           'outlined in\n%s\n' % TAST_DEBUG_DOC)
+          "\nIf you're unsure why this test failed, consult the steps "
+          'outlined in\n%s\n' % TAST_DEBUG_DOC)
       base_result = base_test_result.BaseTestResult(
           test['name'], result, duration=duration_ms, log=error_log)
       suite_results.AddResult(base_result)
@@ -377,7 +384,6 @@ class TastTest(RemoteTest):
     return 0
 
 
-
 class GTestTest(RemoteTest):
 
   # The following list corresponds to paths that should not be copied over to
@@ -431,35 +437,34 @@ class GTestTest(RemoteTest):
         result_dir = '.'
       device_result_file = '/tmp/%s' % result_file
       self._test_cmd += [
-          '--results-src', device_result_file,
-          '--results-dest-dir', result_dir,
+          '--results-src',
+          device_result_file,
+          '--results-dest-dir',
+          result_dir,
       ]
 
     # Build the shell script that will be used on the device to invoke the test.
     device_test_script_contents = self.BASIC_SHELL_SCRIPT[:]
     if self._llvm_profile_var:
       device_test_script_contents += [
-          'export LLVM_PROFILE_FILE=%s'% self._llvm_profile_var,
+          'export LLVM_PROFILE_FILE=%s' % self._llvm_profile_var,
       ]
 
     if self._vpython_dir:
       vpython_spec_path = os.path.relpath(
-          os.path.join(CHROMIUM_SRC_PATH, '.vpython'),
-          self._path_to_outdir)
+          os.path.join(CHROMIUM_SRC_PATH, '.vpython'), self._path_to_outdir)
       # Initialize the vpython cache. This can take 10-20s, and some tests
       # can't afford to wait that long on the first invocation.
       device_test_script_contents.extend([
           'export PATH=$PATH:$PWD/%s' % (self._vpython_dir),
-          'vpython -vpython-spec %s -vpython-tool install' % (
-              vpython_spec_path),
+          'vpython -vpython-spec %s -vpython-tool install' %
+          (vpython_spec_path),
       ])
 
-    test_invocation = (
-        'LD_LIBRARY_PATH=./ ./%s --test-launcher-shard-index=%d '
-        '--test-launcher-total-shards=%d' % (
-            self._test_exe, self._test_launcher_shard_index,
-            self._test_launcher_total_shards)
-    )
+    test_invocation = ('LD_LIBRARY_PATH=./ ./%s --test-launcher-shard-index=%d '
+                       '--test-launcher-total-shards=%d' %
+                       (self._test_exe, self._test_launcher_shard_index,
+                        self._test_launcher_total_shards))
     if self._test_launcher_summary_output:
       test_invocation += ' --test-launcher-summary-output=%s' % (
           device_result_file)
@@ -496,8 +501,8 @@ class GTestTest(RemoteTest):
       # relative to src dir, so fix the path up a bit.
       runtime_files.append(
           os.path.relpath(
-              os.path.abspath(os.path.join(self._path_to_outdir,
-                                           self._vpython_dir)),
+              os.path.abspath(
+                  os.path.join(self._path_to_outdir, self._vpython_dir)),
               CHROMIUM_SRC_PATH))
       # TODO(bpastene): Add the vpython spec to the test's runtime deps instead
       # of handling it here.
@@ -547,17 +552,17 @@ class BrowserSanityTest(RemoteTest):
 
   def build_test_command(self):
     if '--gtest_filter=%s' % SANITY_TEST_TARGET in self._additional_args:
-      logging.info(
-          'GTest filtering not supported for the sanity test. The '
-          '--gtest_filter arg will be ignored.')
+      logging.info('GTest filtering not supported for the sanity test. The '
+                   '--gtest_filter arg will be ignored.')
       self._additional_args.remove('--gtest_filter=%s' % SANITY_TEST_TARGET)
     if any(arg.startswith('--gtest_repeat') for arg in self._additional_args):
       logging.info(
           '--gtest_repeat not supported for sanity test. The arg will be '
           'ignored.')
       self._additional_args = [
-          arg for arg in self._additional_args if not arg.startswith(
-              '--gtest_repeat')]
+          arg for arg in self._additional_args
+          if not arg.startswith('--gtest_repeat')
+      ]
 
     if self._additional_args:
       logging.error(
@@ -572,8 +577,8 @@ class BrowserSanityTest(RemoteTest):
     device_test_script_contents = self.BASIC_SHELL_SCRIPT[:]
     if self._llvm_profile_var:
       device_test_script_contents += [
-          'echo "LLVM_PROFILE_FILE=%s" >> /etc/chrome_dev.conf' % (
-              self._llvm_profile_var)
+          'echo "LLVM_PROFILE_FILE=%s" >> /etc/chrome_dev.conf' %
+          (self._llvm_profile_var)
       ]
 
     # vm_sanity.py is the sanity test, which is baked into the device image.
@@ -583,12 +588,14 @@ class BrowserSanityTest(RemoteTest):
         device_test_script_contents)
 
     self._test_cmd += [
-        '--files', os.path.relpath(self._on_device_script),
+        '--files',
+        os.path.relpath(self._on_device_script),
         # The sanity test smoke-checks the system browser, so deploy our
         # locally-built chrome to the device before testing.
         '--deploy',
         '--mount',
-        '--build-dir', os.path.relpath(self._path_to_outdir, CHROMIUM_SRC_PATH),
+        '--build-dir',
+        os.path.relpath(self._path_to_outdir, CHROMIUM_SRC_PATH),
         '--',
         './' + os.path.relpath(self._on_device_script, self._path_to_outdir)
     ]
@@ -621,23 +628,26 @@ def host_cmd(args, unknown_args):
     raise TestFormatError('Must specify command to run on the host.')
   elif unknown_args:
     raise TestFormatError(
-        'Args "%s" unsupported. Is your host command correctly formatted?' % (
-            ' '.join(unknown_args)))
+        'Args "%s" unsupported. Is your host command correctly formatted?' %
+        (' '.join(unknown_args)))
   elif args.deploy_chrome and not args.path_to_outdir:
     raise TestFormatError(
         '--path-to-outdir must be specified if --deploy-chrome is passed.')
 
   cros_run_test_cmd = [
       CROS_RUN_TEST_PATH,
-      '--board', args.board,
-      '--cache-dir', args.cros_cache,
+      '--board',
+      args.board,
+      '--cache-dir',
+      args.cros_cache,
   ]
   if args.use_vm:
     cros_run_test_cmd += [
         '--start',
         # Don't persist any filesystem changes after the VM shutsdown.
         '--copy-on-write',
-        '--device', 'localhost',
+        '--device',
+        'localhost',
     ]
   else:
     cros_run_test_cmd += [
@@ -658,7 +668,8 @@ def host_cmd(args, unknown_args):
         # Mounting the browser gives it enough disk space to not need stripping.
         '--mount',
         '--nostrip',
-        '--build-dir', os.path.abspath(args.path_to_outdir),
+        '--build-dir',
+        os.path.abspath(args.path_to_outdir),
     ]
 
   cros_run_test_cmd += [
@@ -697,36 +708,47 @@ def add_common_args(*parsers):
     parser.add_argument(
         '--board', type=str, required=True, help='Type of CrOS device.')
     parser.add_argument(
-        '--cros-cache', type=str, default=DEFAULT_CROS_CACHE,
+        '--cros-cache',
+        type=str,
+        default=DEFAULT_CROS_CACHE,
         help='Path to cros cache.')
     parser.add_argument(
-        '--path-to-outdir', type=str, required=True,
+        '--path-to-outdir',
+        type=str,
+        required=True,
         help='Path to output directory, all of whose contents will be '
-             'deployed to the device.')
+        'deployed to the device.')
     parser.add_argument(
-        '--runtime-deps-path', type=str,
+        '--runtime-deps-path',
+        type=str,
         help='Runtime data dependency file from GN.')
     parser.add_argument(
-        '--vpython-dir', type=str,
+        '--vpython-dir',
+        type=str,
         help='Location on host of a directory containing a vpython binary to '
-             'deploy to the device before the test starts. The location of '
-             'this dir will be added onto PATH in the device. WARNING: The '
-             'arch of the device might not match the arch of the host, so '
-             'avoid using "${platform}" when downloading vpython via CIPD.')
+        'deploy to the device before the test starts. The location of '
+        'this dir will be added onto PATH in the device. WARNING: The '
+        'arch of the device might not match the arch of the host, so '
+        'avoid using "${platform}" when downloading vpython via CIPD.')
     # TODO(bpastene): Switch all uses of "--vm-logs-dir" to "--logs-dir".
     parser.add_argument(
-        '--vm-logs-dir', '--logs-dir', type=str, dest='logs_dir',
+        '--vm-logs-dir',
+        '--logs-dir',
+        type=str,
+        dest='logs_dir',
         help='Will copy everything under /var/log/ from the device after the '
-             'test into the specified dir.')
+        'test into the specified dir.')
 
     vm_or_device_group = parser.add_mutually_exclusive_group()
     vm_or_device_group.add_argument(
-        '--use-vm', action='store_true',
+        '--use-vm',
+        action='store_true',
         help='Will run the test in the VM instead of a device.')
     vm_or_device_group.add_argument(
-        '--device', type=str,
+        '--device',
+        type=str,
         help='Hostname (or IP) of device to run the test on. This arg is not '
-             'required if --use-vm is set.')
+        'required if --use-vm is set.')
 
 
 def main():
@@ -736,46 +758,52 @@ def main():
   host_cmd_parser = subparsers.add_parser(
       'host-cmd',
       help='Runs a host-side test. Pass the host-side command to run after '
-           '"--". If --use-vm is passed, hostname and port for the device '
-           'will be 127.0.0.1:9222.')
+      '"--". If --use-vm is passed, hostname and port for the device '
+      'will be 127.0.0.1:9222.')
   host_cmd_parser.set_defaults(func=host_cmd)
   host_cmd_parser.add_argument(
-      '--deploy-chrome', action='store_true',
+      '--deploy-chrome',
+      action='store_true',
       help='Will deploy a locally built Chrome binary to the device before '
-           'running the host-cmd.')
+      'running the host-cmd.')
   host_cmd_parser.add_argument('cmd', nargs=argparse.REMAINDER)
   # GTest args.
   # TODO(bpastene): Rename 'vm-test' arg to 'gtest'.
   gtest_parser = subparsers.add_parser(
-      'vm-test',
-      help='Runs a device-side gtest.')
+      'vm-test', help='Runs a device-side gtest.')
   gtest_parser.set_defaults(func=device_test)
   gtest_parser.add_argument(
-      '--test-exe', type=str, required=True,
+      '--test-exe',
+      type=str,
+      required=True,
       help='Path to test executable to run inside the device. If the value is '
-           '%s, the sanity test that ships with the device image runs instead. '
-           'This test smokes-check the system browser (eg: loads a simple '
-           'webpage, executes some javascript), so a fully-built Chrome binary '
-           'that can get deployed to the device is expected to be available in '
-           'the out-dir.' % SANITY_TEST_TARGET)
+      '%s, the sanity test that ships with the device image runs instead. '
+      'This test smokes-check the system browser (eg: loads a simple '
+      'webpage, executes some javascript), so a fully-built Chrome binary '
+      'that can get deployed to the device is expected to be available in '
+      'the out-dir.' % SANITY_TEST_TARGET)
 
   # GTest args. Some are passed down to the test binary in the device. Others
   # are parsed here since they might need tweaking or special handling.
   gtest_parser.add_argument(
-      '--test-launcher-summary-output', type=str,
+      '--test-launcher-summary-output',
+      type=str,
       help='When set, will pass the same option down to the test and retrieve '
-           'its result file at the specified location.')
+      'its result file at the specified location.')
   # Shard args are parsed here since we might also specify them via env vars.
   gtest_parser.add_argument(
       '--test-launcher-shard-index',
-      type=int, default=os.environ.get('GTEST_SHARD_INDEX', 0),
+      type=int,
+      default=os.environ.get('GTEST_SHARD_INDEX', 0),
       help='Index of the external shard to run.')
   gtest_parser.add_argument(
       '--test-launcher-total-shards',
-      type=int, default=os.environ.get('GTEST_TOTAL_SHARDS', 1),
+      type=int,
+      default=os.environ.get('GTEST_TOTAL_SHARDS', 1),
       help='Total number of external shards.')
   gtest_parser.add_argument(
-      '--stop-ui', action='store_true',
+      '--stop-ui',
+      action='store_true',
       help='Will stop the UI service in the device before running the test.')
 
   # Tast test args.
@@ -783,23 +811,33 @@ def main():
   tast_test_parser = subparsers.add_parser(
       'tast',
       help='Runs a device-side set of Tast tests. For more details, see: '
-           'https://chromium.googlesource.com/chromiumos/platform/tast/+/master/docs/running_tests.md')
+      'https://chromium.googlesource.com/chromiumos/platform/tast/+/master/docs/running_tests.md'
+  )
   tast_test_parser.set_defaults(func=device_test)
   tast_test_parser.add_argument(
-      '--suite-name', type=str, required=True,
+      '--suite-name',
+      type=str,
+      required=True,
       help='Name to apply to the set of Tast tests to run. This has no effect '
-           'on what is executed, but is used mainly for test results reporting '
-           'and tracking (eg: flakiness dashboard).')
+      'on what is executed, but is used mainly for test results reporting '
+      'and tracking (eg: flakiness dashboard).')
   tast_test_parser.add_argument(
-      '--test-launcher-summary-output', type=str,
+      '--test-launcher-summary-output',
+      type=str,
       help='Generates a simple GTest-style JSON result file for the test run.')
   # TODO(bpastene): Change all uses of "--conditional" to use "--attr-expr".
   tast_test_parser.add_argument(
-      '--conditional', '--attr-expr', type=str, dest='conditional',
+      '--conditional',
+      '--attr-expr',
+      type=str,
+      dest='conditional',
       help='A boolean expression whose matching tests will run '
-           '(eg: ("dep:chrome")).')
+      '(eg: ("dep:chrome")).')
   tast_test_parser.add_argument(
-      '--test', '-t', action='append', dest='tests',
+      '--test',
+      '-t',
+      action='append',
+      dest='tests',
       help='A Tast test to run in the device (eg: "ui.ChromeLogin").')
 
   add_common_args(gtest_parser, tast_test_parser, host_cmd_parser)
@@ -815,8 +853,8 @@ def main():
     try:
       socket.getaddrinfo(LAB_DUT_HOSTNAME, None)
     except socket.gaierror:
-      logging.error(
-          'The default DUT hostname of %s is unreachable.', LAB_DUT_HOSTNAME)
+      logging.error('The default DUT hostname of %s is unreachable.',
+                    LAB_DUT_HOSTNAME)
       return 1
   if args.use_vm:
     if not os.path.exists('/dev/kvm'):