1 # Copyright 2013 The Chromium Authors. All rights reserved.
2 # Use of this source code is governed by a BSD-style license that can be
3 # found in the LICENSE file.
6 Utility functions for working with the Feature abstraction. Features are grouped
7 into a dictionary by name. Each Feature is guaranteed to have the following two
9 name - a string, the name of the feature
10 platform - a list containing 'apps' or 'extensions', both, or neither.
12 A Feature may have other keys from a _features.json file as well. Features with
13 a whitelist are ignored as they are only useful to specific apps or extensions.
18 from branch_utility import BranchUtility
21 def _GetPlatformsForExtensionTypes(extension_types):
23 if extension_types == 'all' or 'platform_app' in extension_types:
24 platforms.append('apps')
25 if extension_types == 'all' or 'extension' in extension_types:
26 platforms.append('extensions')
30 def Parse(features_json):
31 '''Process JSON from a _features.json file, standardizing it into a dictionary
36 def ignore_feature(name, value):
37 '''Returns true if this feature should be ignored. Features are ignored if
38 they are only available to whitelisted apps or component extensions/apps, as
39 in these cases the APIs are not available to public developers.
41 Private APIs are also unavailable to public developers, but logic elsewhere
42 makes sure they are not listed. So they shouldn't be ignored via this
45 if name.endswith('Private'):
47 return value.get('location') == 'component' or 'whitelist' in value
49 for name, rawvalue in features_json.iteritems():
50 # Some feature names correspond to a list, typically because they're
51 # whitelisted in stable for certain extensions and available in dev for
52 # everybody else. Force a list down to a single feature by attempting to
53 # remove the entries that don't affect the typical usage of an API.
54 if isinstance(rawvalue, list):
55 available_values = [subvalue for subvalue in rawvalue
56 if not ignore_feature(name, subvalue)]
57 if not available_values:
60 if len(available_values) == 1:
61 value = available_values[0]
63 # Multiple available values probably implies different feature
64 # configurations for apps vs extensions. Currently, this is 'commands'.
65 # To get the ball rolling, add a hack to combine the extension types.
66 # See http://crbug.com/316194.
67 extension_types = set()
68 for available_value in available_values:
69 extension_types.update(available_value.get('extension_types', ()))
71 # For the base value, select the one with the most recent availability.
72 channel_names = BranchUtility.GetAllChannelNames()
73 available_values.sort(
74 key=lambda v: channel_names.index(v.get('channel', 'stable')))
76 # Note: copy() is enough because only a single toplevel key is modified.
77 value = copy(available_values[0])
78 value['extension_types'] = list(extension_types)
82 if ignore_feature(name, value):
85 # Now we transform 'extension_types' into the more useful 'platforms'.
87 # But first, note that 'platforms' has a double meaning. In the docserver
88 # model (what we're in the process of generating) it means 'apps' vs
89 # 'extensions'. In the JSON features as read from Chrome it means 'win' vs
90 # 'mac'. Ignore the latter.
91 value.pop('platforms', None)
92 extension_types = value.pop('extension_types', None)
95 if extension_types is not None:
96 platforms = _GetPlatformsForExtensionTypes(extension_types)
100 'platforms': platforms,
102 features[name].update(value)
107 def Filtered(features, platform):
108 '''Create a new Features dictionary from |features| that contains only items
109 relevant to |platform|. Feature values are unmodified; callers should
110 deepcopy() if they need to modify them.
112 return dict((name, feature) for name, feature in features.iteritems()
113 if platform in feature['platforms'])
116 def MergedWith(features, other):
117 '''Merge |features| with an additional dictionary to create a new features
118 dictionary. If a feature is common to both |features| and |other|, then it is
119 merged using the standard dictionary update instead of being overwritten.
120 Returns the new Features dictionary.
122 for key, value in other.iteritems():
124 features[key].update(value)
126 features[key] = value
128 # Ensure the Feature schema is enforced for all added items.
129 if not 'name' in features[key]:
130 features[key]['name'] = key
131 if not 'platforms' in features[key]:
132 features[key]['platforms'] = []