Generate a static struct from fieldtrial_testing_config

tools/variations/fieldtrial_to_struct.py

Index: tools/variations/fieldtrial_to_struct.py
diff --git a/tools/variations/fieldtrial_to_struct.py b/tools/variations/fieldtrial_to_struct.py
new file mode 100644
index 0000000000000000000000000000000000000000..7e134ab49f050fcbd3efccadc6756b055f8eaaf1
--- /dev/null
+++ b/tools/variations/fieldtrial_to_struct.py
@@ -0,0 +1,89 @@
+#!/usr/bin/env python
+# Copyright 2015 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 json
+import os.path
+import sys
+import optparse
+_script_path = os.path.realpath(__file__)
+
+sys.path.insert(0, os.path.normpath(_script_path + "/../../json_comment_eater"))
+try:
+  import json_comment_eater
+finally:
+  sys.path.pop(0)
+
+sys.path.insert(0, os.path.normpath(_script_path + "/../../json_to_struct"))
+try:
+  import json_to_struct
+finally:
+  sys.path.pop(0)
+
+def _Load(filename):
+  """Loads a JSON file into a Python object and return this object.
+  """
+  with open(filename, 'r') as handle:
+    result = json.loads(json_comment_eater.Nom(handle.read()))
+  return result
+
+def _LoadFieldTrialConfig(filename):
+  """Loads a field trial config JSON and converts it into a format that can be
+  used by json_to_struct.
+  """
+  element = {'groups': []}
+  with open(filename, 'r') as handle:
+    config = json.loads(json_comment_eater.Nom(handle.read()))
+    for study in config:
+      group_data = config[study][0]
+      group = {
+        'study': study,
+        'group_name': group_data['group_name']
+      }
+      params_data = group_data.get('params')
+      if (params_data):
+        params = []
+        for param in params_data:
+          params.append({'key': param, 'value': params_data[param]})
+        group['params'] = params
+      element['groups'].append(group)
+  return {'elements': {'kFieldTrialConfig': element}}
+
+if __name__ == '__main__':
+  parser = optparse.OptionParser(
+      description='Generates an C++ array of struct from a JSON description.',
+      usage='usage: %prog [option] -s schema description')
+  parser.add_option('-b', '--destbase',
+      help='base directory of generated files.')
+  parser.add_option('-d', '--destdir',
+      help='directory to output generated files, relative to destbase.')
+  parser.add_option('-n', '--namespace',
+      help='C++ namespace for generated files. e.g search_providers.')
+  parser.add_option('-s', '--schema', help='path to the schema file, '
+      'mandatory.')
+  parser.add_option('-o', '--output', help='output filename, '
+      'mandatory.')
+  (opts, args) = parser.parse_args()
+
+  if not opts.schema:
+    parser.error('You must specify a --schema.')
+
+  description_filename = os.path.normpath(args[0])
+  root, ext = os.path.splitext(description_filename)
+  shortroot = opts.output
+  if opts.destdir:
+    output_root = os.path.join(os.path.normpath(opts.destdir), shortroot)
+  else:
+    output_root = shortroot
+
+  if opts.destbase:
+    basepath = os.path.normpath(opts.destbase)
+  else:
+    basepath = ''
+
+  schema = _Load(opts.schema)
+  description = _LoadFieldTrialConfig(description_filename)
+  json_to_struct.GenerateStruct(

[Alexei Svitkine (slow), 2015/07/08 16:54:54]

Can you add some tests for this implementation? I'd like to see mock inputs +
tests for expected C++ output.

[danduong, 2015/07/09 00:12:54]

I added a unittest for the most interesting part of the code (conversion of
fieldtrial_testing_config into a description format). My thought is that most of
the machinery is already covered by the other unit tests.

[Alexei Svitkine (slow), 2015/07/09 16:55:32]

I think it's worth having a test with an expectation for the resulting C++ code.
This way, we know exactly what's being generated and won't be bitten by changes
to the underlying machinery that may break us silently.

+      basepath, output_root, opts.namespace, schema, description,
+      description_filename, opts.schema)