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1# Copyright 2018 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.
4
5"""Helpers for processing conditionally enabled features in a mojom."""
6
7from . import ast
8from ..error import Error
9
10class EnableIfError(Error):
11  """ Class for errors from ."""
12
13  def __init__(self, filename, message, lineno=None):
14    Error.__init__(self, filename, message, lineno=lineno, addenda=None)
15
16def _IsEnabled(definition, enabled_features):
17  """Returns true if a definition is enabled.
18
19  A definition is enabled if it has no EnableIf attribute, or if the value of
20  the EnableIf attribute is in enabled_features.
21  """
22  if not hasattr(definition, "attribute_list"):
23    return True
24  if not definition.attribute_list:
25    return True
26
27  already_defined = False
28  for a in definition.attribute_list:
29    if a.key == 'EnableIf':
30      if already_defined:
31        raise EnableIfError(definition.filename,
32          "EnableIf attribute may only be defined once per field.",
33          definition.lineno)
34      already_defined = True
35
36  for attribute in definition.attribute_list:
37    if attribute.key == 'EnableIf' and attribute.value not in enabled_features:
38      return False
39  return True
40
41
42def _FilterDisabledFromNodeList(node_list, enabled_features):
43  if not node_list:
44    return
45  assert isinstance(node_list, ast.NodeListBase)
46  node_list.items = [
47      item for item in node_list.items if _IsEnabled(item, enabled_features)
48  ]
49  for item in node_list.items:
50    _FilterDefinition(item, enabled_features)
51
52
53def _FilterDefinition(definition, enabled_features):
54  """Filters definitions with a body."""
55  if isinstance(definition, ast.Enum):
56    _FilterDisabledFromNodeList(definition.enum_value_list, enabled_features)
57  elif isinstance(definition, ast.Interface):
58    _FilterDisabledFromNodeList(definition.body, enabled_features)
59  elif isinstance(definition, ast.Method):
60    _FilterDisabledFromNodeList(definition.parameter_list, enabled_features)
61    _FilterDisabledFromNodeList(definition.response_parameter_list,
62                                enabled_features)
63  elif isinstance(definition, ast.Struct):
64    _FilterDisabledFromNodeList(definition.body, enabled_features)
65  elif isinstance(definition, ast.Union):
66    _FilterDisabledFromNodeList(definition.body, enabled_features)
67
68
69def RemoveDisabledDefinitions(mojom, enabled_features):
70  """Removes conditionally disabled definitions from a Mojom node."""
71  mojom.import_list = ast.ImportList([
72    imported_file for imported_file in mojom.import_list
73      if _IsEnabled(imported_file, enabled_features)
74  ])
75  mojom.definition_list = [
76      definition for definition in mojom.definition_list
77          if _IsEnabled(definition, enabled_features)
78  ]
79  for definition in mojom.definition_list:
80    _FilterDefinition(definition, enabled_features)
81