Dump empty json to output when no shard json file is given.

build/android/pylib/results/presentation/test_results_presentation.py

 #! /usr/bin/env python
 #
 # Copyright 2017 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.
 
 import argparse
 import collections
 import json
 import tempfile
@@ skipping 288 matching lines @@
         test_name, builder_name, build_number,
         time.strftime('%Y_%m_%d_T%H_%M_%S'))
     gsutil_path = os.path.join(BASE_DIR, 'third_party', 'catapult',
                                'third_party', 'gsutil', 'gsutil.py')
     subprocess.check_call([
         sys.executable, gsutil_path, '-h', "Content-Type:%s" % content_type,
         'cp', temp_file.name, 'gs://%s/%s' % (bucket, dest)])
 
   return '%s/%s/%s' % (server_url, bucket, dest)
 
+
 def main():
   parser = argparse.ArgumentParser()
   parser.add_argument('--json-file', help='Path of json file.')
   parser.add_argument('--cs-base-url', help='Base url for code search.',
                       default='http://cs.chromium.org')
   parser.add_argument('--bucket', help='Google storage bucket.', required=True)
   parser.add_argument('--builder-name', help='Builder name.')
   parser.add_argument('--build-number', help='Build number.')
   parser.add_argument('--test-name', help='The name of the test.',
                       required=True)
@@ skipping 21 matching lines @@
            ' --task-summary-json=XXX command.)')
   parser.add_argument(
       'positional', nargs='*',
       help='output.json from shards.')
 
   args = parser.parse_args()
 
   if ((args.build_properties is None) ==
          (args.build_number is None or args.builder_name is None)):
     raise parser.error('Exactly one of build_perperties or '
-                    '(build_number or builder_names) should be given.')
+                       '(build_number or builder_name) should be given.')
 
   if (args.build_number is None) != (args.builder_name is None):
     raise parser.error('args.build_number and args.builder_name '
-                    'has to be be given together'
-                    'or not given at all.')
+                       'has to be be given together'
+                       'or not given at all.')
 
   if (len(args.positional) == 0) == (args.json_file is None):
-    raise parser.error('Exactly one of args.positional and '
-                    'args.json_file should be given.')
+    if args.json_file:

[jbudorick, 2017/04/27 18:40:37]

Given that you're handling the two cases differently, this might be a bit more
readable if we just split it into two conditions at the top level, e.g.

  if len(args.positional) == 0 and args.json_file is None:
    if args.output_json:
      ...
  elif len(args.positional) != 0 and args.json_file:
    raise parser.error(...)

[BigBossZhiling, 2017/04/27 20:41:49]

Done.

+      raise parser.error('Exactly one of args.positional and '
+                         'args.json_file should be given.')
+    else:
+      if args.output_json:
+        with open(args.output_json, 'w') as f:
+          f.write('{}')

[jbudorick, 2017/04/27 18:40:37]

nit: json.dump({}, f)

I know the result is the same, but I think it's a bit more clear.

[BigBossZhiling, 2017/04/27 20:41:49]

Done.

+      return
 
   if args.build_properties:
     build_properties = json.loads(args.build_properties)
     if ((not 'buildnumber' in build_properties) or
         (not 'buildername' in build_properties)):
       raise parser.error('Build number/builder name not specified.')
     build_number = build_properties['buildnumber']
     builder_name = build_properties['buildername']
   elif args.build_number and args.builder_name:
     build_number = args.build_number
@@ skipping 21 matching lines @@
     with open(json_file) as original_json_file:
       json_object = json.load(original_json_file)
       json_object['links'] = {'result_details': result_details_link}
       with open(args.output_json, 'w') as f:
         json.dump(json_object, f)
   else:
     print result_details_link
 
 if __name__ == '__main__':
   sys.exit(main())