src/third_party/WebKit/Source/bindings/scripts/v8_attributes.py

   1 # Copyright (C) 2013 Google Inc. All rights reserved.
   2 #
   3 # Redistribution and use in source and binary forms, with or without
   4 # modification, are permitted provided that the following conditions are
   5 # met:
   6 #
   7 #     * Redistributions of source code must retain the above copyright
   8 # notice, this list of conditions and the following disclaimer.
   9 #     * Redistributions in binary form must reproduce the above
  10 # copyright notice, this list of conditions and the following disclaimer
  11 # in the documentation and/or other materials provided with the
  12 # distribution.
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  14 # contributors may be used to endorse or promote products derived from
  15 # this software without specific prior written permission.
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  18 # "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  19 # LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  20 # A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  21 # OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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  25 # THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  26 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  27 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  28
  29 """Generate template values for attributes.
  30
  31 Extends IdlType with property |constructor_type_name|.
  32
  33 Design doc: http://www.chromium.org/developers/design-documents/idl-compiler
  34 """
  35
  36 import idl_types
  37 from idl_types import inherits_interface
  38 from v8_globals import includes, interfaces
  39 import v8_types
  40 import v8_utilities
  41 from v8_utilities import (capitalize, cpp_name, has_extended_attribute,
  42                           has_extended_attribute_value, scoped_name, strip_suffix,
  43                           uncapitalize, extended_attribute_value_as_list)
  44
  45
  46 def attribute_context(interface, attribute):
  47     idl_type = attribute.idl_type
  48     base_idl_type = idl_type.base_type
  49     extended_attributes = attribute.extended_attributes
  50
  51     idl_type.add_includes_for_type()
  52
  53     # [CheckSecurity]
  54     is_check_security_for_node = 'CheckSecurity' in extended_attributes
  55     if is_check_security_for_node:
  56         includes.add('bindings/core/v8/BindingSecurity.h')
  57     # [CustomElementCallbacks], [Reflect]
  58     is_custom_element_callbacks = 'CustomElementCallbacks' in extended_attributes
  59     is_reflect = 'Reflect' in extended_attributes
  60     if is_custom_element_callbacks or is_reflect:
  61         includes.add('core/dom/custom/CustomElementProcessingStack.h')
  62     # [PerWorldBindings]
  63     if 'PerWorldBindings' in extended_attributes:
  64         assert idl_type.is_wrapper_type or 'LogActivity' in extended_attributes, '[PerWorldBindings] should only be used with wrapper types: %s.%s' % (interface.name, attribute.name)
  65     # [TypeChecking]
  66     has_type_checking_unrestricted = (
  67         (has_extended_attribute_value(interface, 'TypeChecking', 'Unrestricted') or
  68          has_extended_attribute_value(attribute, 'TypeChecking', 'Unrestricted')) and
  69          idl_type.name in ('Float', 'Double'))
  70     # [ImplementedInPrivateScript]
  71     is_implemented_in_private_script = 'ImplementedInPrivateScript' in extended_attributes
  72     if is_implemented_in_private_script:
  73         includes.add('bindings/core/v8/PrivateScriptRunner.h')
  74         includes.add('core/frame/LocalFrame.h')
  75         includes.add('platform/ScriptForbiddenScope.h')
  76
  77     # [OnlyExposedToPrivateScript]
  78     is_only_exposed_to_private_script = 'OnlyExposedToPrivateScript' in extended_attributes
  79
  80     if (base_idl_type == 'EventHandler' and
  81         interface.name in ['Window', 'WorkerGlobalScope'] and
  82         attribute.name == 'onerror'):
  83         includes.add('bindings/core/v8/V8ErrorHandler.h')
  84
  85     context = {
  86         'access_control_list': access_control_list(attribute),
  87         'activity_logging_world_list_for_getter': v8_utilities.activity_logging_world_list(attribute, 'Getter'),  # [ActivityLogging]
  88         'activity_logging_world_list_for_setter': v8_utilities.activity_logging_world_list(attribute, 'Setter'),  # [ActivityLogging]
  89         'activity_logging_world_check': v8_utilities.activity_logging_world_check(attribute),  # [ActivityLogging]
  90         'argument_cpp_type': idl_type.cpp_type_args(used_as_rvalue_type=True),
  91         'cached_attribute_validation_method': extended_attributes.get('CachedAttribute'),
  92         'conditional_string': v8_utilities.conditional_string(attribute),
  93         'constructor_type': idl_type.constructor_type_name
  94                             if is_constructor_attribute(attribute) else None,
  95         'cpp_name': cpp_name(attribute),
  96         'cpp_type': idl_type.cpp_type,
  97         'cpp_type_initializer': idl_type.cpp_type_initializer,
  98         'deprecate_as': v8_utilities.deprecate_as(attribute),  # [DeprecateAs]
  99         'enum_validation_expression': idl_type.enum_validation_expression,
 100         'exposed_test': v8_utilities.exposed(attribute, interface),  # [Exposed]
 101         'has_custom_getter': has_custom_getter(attribute),
 102         'has_custom_setter': has_custom_setter(attribute),
 103         'has_type_checking_unrestricted': has_type_checking_unrestricted,
 104         'idl_type': str(idl_type),  # need trailing [] on array for Dictionary::ConversionContext::setConversionType
 105         'is_call_with_execution_context': v8_utilities.has_extended_attribute_value(attribute, 'CallWith', 'ExecutionContext'),
 106         'is_call_with_script_state': v8_utilities.has_extended_attribute_value(attribute, 'CallWith', 'ScriptState'),
 107         'is_check_security_for_node': is_check_security_for_node,
 108         'is_custom_element_callbacks': is_custom_element_callbacks,
 109         'is_expose_js_accessors': 'ExposeJSAccessors' in extended_attributes,
 110         'is_getter_raises_exception':  # [RaisesException]
 111             'RaisesException' in extended_attributes and
 112             extended_attributes['RaisesException'] in (None, 'Getter'),
 113         'is_implemented_in_private_script': is_implemented_in_private_script,
 114         'is_initialized_by_event_constructor':
 115             'InitializedByEventConstructor' in extended_attributes,
 116         'is_keep_alive_for_gc': is_keep_alive_for_gc(interface, attribute),
 117         'is_nullable': idl_type.is_nullable,
 118         'is_explicit_nullable': idl_type.is_explicit_nullable,
 119         'is_partial_interface_member':
 120             'PartialInterfaceImplementedAs' in extended_attributes,
 121         'is_per_world_bindings': 'PerWorldBindings' in extended_attributes,
 122         'is_read_only': attribute.is_read_only,
 123         'is_reflect': is_reflect,
 124         'is_replaceable': 'Replaceable' in attribute.extended_attributes,
 125         'is_static': attribute.is_static,
 126         'is_url': 'URL' in extended_attributes,
 127         'is_unforgeable': 'Unforgeable' in extended_attributes,
 128         'measure_as': v8_utilities.measure_as(attribute),  # [MeasureAs]
 129         'name': attribute.name,
 130         'only_exposed_to_private_script': is_only_exposed_to_private_script,
 131         'per_context_enabled_function': v8_utilities.per_context_enabled_function_name(attribute),  # [PerContextEnabled]
 132         'private_script_v8_value_to_local_cpp_value': idl_type.v8_value_to_local_cpp_value(
 133             extended_attributes, 'v8Value', 'cppValue', isolate='scriptState->isolate()', used_in_private_script=True),
 134         'property_attributes': property_attributes(attribute),
 135         'put_forwards': 'PutForwards' in extended_attributes,
 136         'reflect_empty': extended_attributes.get('ReflectEmpty'),
 137         'reflect_invalid': extended_attributes.get('ReflectInvalid', ''),
 138         'reflect_missing': extended_attributes.get('ReflectMissing'),
 139         'reflect_only': extended_attribute_value_as_list(attribute, 'ReflectOnly'),
 140         'runtime_enabled_function': v8_utilities.runtime_enabled_function_name(attribute),  # [RuntimeEnabled]
 141         'setter_callback': setter_callback_name(interface, attribute),
 142         'should_be_exposed_to_script': not (is_implemented_in_private_script and is_only_exposed_to_private_script),
 143         'world_suffixes': ['', 'ForMainWorld']
 144                           if 'PerWorldBindings' in extended_attributes
 145                           else [''],  # [PerWorldBindings]
 146     }
 147
 148     if is_constructor_attribute(attribute):
 149         constructor_getter_context(interface, attribute, context)
 150         return context
 151     if not has_custom_getter(attribute):
 152         getter_context(interface, attribute, context)
 153     if (not has_custom_setter(attribute) and
 154         (not attribute.is_read_only or 'PutForwards' in extended_attributes)):
 155         setter_context(interface, attribute, context)
 156
 157     return context
 158
 159
 160 ################################################################################
 161 # Getter
 162 ################################################################################
 163
 164 def getter_context(interface, attribute, context):
 165     idl_type = attribute.idl_type
 166     base_idl_type = idl_type.base_type
 167     extended_attributes = attribute.extended_attributes
 168
 169     cpp_value = getter_expression(interface, attribute, context)
 170     # Normally we can inline the function call into the return statement to
 171     # avoid the overhead of using a Ref<> temporary, but for some cases
 172     # (nullable types, EventHandler, [CachedAttribute], or if there are
 173     # exceptions), we need to use a local variable.
 174     # FIXME: check if compilers are smart enough to inline this, and if so,
 175     # always use a local variable (for readability and CG simplicity).
 176     release = False
 177     if 'ImplementedInPrivateScript' in extended_attributes:
 178         if (not idl_type.is_wrapper_type and
 179             not idl_type.is_basic_type and
 180             not idl_type.is_enum):
 181             raise Exception('Private scripts supports only primitive types and DOM wrappers.')
 182
 183         context['cpp_value_original'] = cpp_value
 184         cpp_value = 'result'
 185         # EventHandler has special handling
 186         if base_idl_type != 'EventHandler':
 187             release = idl_type.release
 188     elif (idl_type.is_explicit_nullable or
 189         base_idl_type == 'EventHandler' or
 190         'CachedAttribute' in extended_attributes or
 191         'ReflectOnly' in extended_attributes or
 192         context['is_keep_alive_for_gc'] or
 193         context['is_getter_raises_exception']):
 194         context['cpp_value_original'] = cpp_value
 195         cpp_value = 'cppValue'
 196         # EventHandler has special handling
 197         if base_idl_type != 'EventHandler':
 198             release = idl_type.release
 199
 200     def v8_set_return_value_statement(for_main_world=False):
 201         if context['is_keep_alive_for_gc']:
 202             return 'v8SetReturnValue(info, wrapper)'
 203         return idl_type.v8_set_return_value(cpp_value, extended_attributes=extended_attributes, script_wrappable='impl', release=release, for_main_world=for_main_world)
 204
 205     context.update({
 206         'cpp_value': cpp_value,
 207         'cpp_value_to_v8_value': idl_type.cpp_value_to_v8_value(
 208             cpp_value=cpp_value, creation_context='info.Holder()',
 209             extended_attributes=extended_attributes),
 210         'v8_set_return_value_for_main_world': v8_set_return_value_statement(for_main_world=True),
 211         'v8_set_return_value': v8_set_return_value_statement(),
 212     })
 213
 214
 215 def getter_expression(interface, attribute, context):
 216     arguments = []
 217     this_getter_base_name = getter_base_name(interface, attribute, arguments)
 218     getter_name = scoped_name(interface, attribute, this_getter_base_name)
 219
 220     if 'ImplementedInPrivateScript' in attribute.extended_attributes:
 221         arguments.append('toFrameIfNotDetached(info.GetIsolate()->GetCurrentContext())')
 222         arguments.append('impl')
 223         arguments.append('&result')
 224     arguments.extend(v8_utilities.call_with_arguments(
 225         attribute.extended_attributes.get('CallWith')))
 226     # Members of IDL partial interface definitions are implemented in C++ as
 227     # static member functions, which for instance members (non-static members)
 228     # take *impl as their first argument
 229     if ('PartialInterfaceImplementedAs' in attribute.extended_attributes and
 230         not 'ImplementedInPrivateScript' in attribute.extended_attributes and
 231         not attribute.is_static):
 232         arguments.append('*impl')
 233     if attribute.idl_type.is_explicit_nullable:
 234         arguments.append('isNull')
 235     if context['is_getter_raises_exception']:
 236         arguments.append('exceptionState')
 237     return '%s(%s)' % (getter_name, ', '.join(arguments))
 238
 239
 240 CONTENT_ATTRIBUTE_GETTER_NAMES = {
 241     'boolean': 'fastHasAttribute',
 242     'long': 'getIntegralAttribute',
 243     'unsigned long': 'getUnsignedIntegralAttribute',
 244 }
 245
 246
 247 def getter_base_name(interface, attribute, arguments):
 248     extended_attributes = attribute.extended_attributes
 249
 250     if 'ImplementedInPrivateScript' in extended_attributes:
 251         return '%sAttributeGetter' % uncapitalize(cpp_name(attribute))
 252
 253     if 'Reflect' not in extended_attributes:
 254         return uncapitalize(cpp_name(attribute))
 255
 256     content_attribute_name = extended_attributes['Reflect'] or attribute.name.lower()
 257     if content_attribute_name in ['class', 'id', 'name']:
 258         # Special-case for performance optimization.
 259         return 'get%sAttribute' % content_attribute_name.capitalize()
 260
 261     arguments.append(scoped_content_attribute_name(interface, attribute))
 262
 263     base_idl_type = attribute.idl_type.base_type
 264     if base_idl_type in CONTENT_ATTRIBUTE_GETTER_NAMES:
 265         return CONTENT_ATTRIBUTE_GETTER_NAMES[base_idl_type]
 266     if 'URL' in attribute.extended_attributes:
 267         return 'getURLAttribute'
 268     return 'fastGetAttribute'
 269
 270
 271 def is_keep_alive_for_gc(interface, attribute):
 272     idl_type = attribute.idl_type
 273     base_idl_type = idl_type.base_type
 274     extended_attributes = attribute.extended_attributes
 275     return (
 276         # For readonly attributes, for performance reasons we keep the attribute
 277         # wrapper alive while the owner wrapper is alive, because the attribute
 278         # never changes.
 279         (attribute.is_read_only and
 280          idl_type.is_wrapper_type and
 281          # There are some exceptions, however:
 282          not(
 283              # Node lifetime is managed by object grouping.
 284              inherits_interface(interface.name, 'Node') or
 285              inherits_interface(base_idl_type, 'Node') or
 286              # A self-reference is unnecessary.
 287              attribute.name == 'self' or
 288              # FIXME: Remove these hard-coded hacks.
 289              base_idl_type in ['EventTarget', 'Window'] or
 290              base_idl_type.startswith(('HTML', 'SVG')))))
 291
 292
 293 ################################################################################
 294 # Setter
 295 ################################################################################
 296
 297 def setter_context(interface, attribute, context):
 298     if 'PutForwards' in attribute.extended_attributes:
 299         # Use target interface and attribute in place of original interface and
 300         # attribute from this point onwards.
 301         target_interface_name = attribute.idl_type.base_type
 302         target_attribute_name = attribute.extended_attributes['PutForwards']
 303         interface = interfaces[target_interface_name]
 304         try:
 305             attribute = next(candidate
 306                              for candidate in interface.attributes
 307                              if candidate.name == target_attribute_name)
 308         except StopIteration:
 309             raise Exception('[PutForward] target not found:\n'
 310                             'Attribute "%s" is not present in interface "%s"' %
 311                             (target_attribute_name, target_interface_name))
 312
 313     extended_attributes = attribute.extended_attributes
 314     idl_type = attribute.idl_type
 315
 316     # [RaisesException], [RaisesException=Setter]
 317     is_setter_raises_exception = (
 318         'RaisesException' in extended_attributes and
 319         extended_attributes['RaisesException'] in [None, 'Setter'])
 320     # [TypeChecking=Interface]
 321     has_type_checking_interface = (
 322         (has_extended_attribute_value(interface, 'TypeChecking', 'Interface') or
 323          has_extended_attribute_value(attribute, 'TypeChecking', 'Interface')) and
 324         idl_type.is_wrapper_type)
 325
 326     context.update({
 327         'has_setter_exception_state':
 328             is_setter_raises_exception or has_type_checking_interface or
 329             context['has_type_checking_unrestricted'] or
 330             idl_type.v8_conversion_needs_exception_state,
 331         'has_type_checking_interface': has_type_checking_interface,
 332         'is_setter_call_with_execution_context': v8_utilities.has_extended_attribute_value(
 333             attribute, 'SetterCallWith', 'ExecutionContext'),
 334         'is_setter_raises_exception': is_setter_raises_exception,
 335         'private_script_cpp_value_to_v8_value': idl_type.cpp_value_to_v8_value(
 336             'cppValue', isolate='scriptState->isolate()',
 337             creation_context='scriptState->context()->Global()'),
 338         'v8_value_to_local_cpp_value': idl_type.v8_value_to_local_cpp_value(
 339             extended_attributes, 'v8Value', 'cppValue'),
 340     })
 341
 342     # setter_expression() depends on context values we set above.
 343     context['cpp_setter'] = setter_expression(interface, attribute, context)
 344
 345
 346 def setter_expression(interface, attribute, context):
 347     extended_attributes = attribute.extended_attributes
 348     arguments = v8_utilities.call_with_arguments(
 349         extended_attributes.get('SetterCallWith') or
 350         extended_attributes.get('CallWith'))
 351
 352     this_setter_base_name = setter_base_name(interface, attribute, arguments)
 353     setter_name = scoped_name(interface, attribute, this_setter_base_name)
 354
 355     # Members of IDL partial interface definitions are implemented in C++ as
 356     # static member functions, which for instance members (non-static members)
 357     # take *impl as their first argument
 358     if ('PartialInterfaceImplementedAs' in extended_attributes and
 359         not 'ImplementedInPrivateScript' in extended_attributes and
 360         not attribute.is_static):
 361         arguments.append('*impl')
 362     idl_type = attribute.idl_type
 363     if 'ImplementedInPrivateScript' in extended_attributes:
 364         arguments.append('toFrameIfNotDetached(info.GetIsolate()->GetCurrentContext())')
 365         arguments.append('impl')
 366         arguments.append('cppValue')
 367     elif idl_type.base_type == 'EventHandler':
 368         getter_name = scoped_name(interface, attribute, cpp_name(attribute))
 369         context['event_handler_getter_expression'] = '%s(%s)' % (
 370             getter_name, ', '.join(arguments))
 371         if (interface.name in ['Window', 'WorkerGlobalScope'] and
 372             attribute.name == 'onerror'):
 373             includes.add('bindings/core/v8/V8ErrorHandler.h')
 374             arguments.append('V8EventListenerList::findOrCreateWrapper<V8ErrorHandler>(v8Value, true, ScriptState::current(info.GetIsolate()))')
 375         else:
 376             arguments.append('V8EventListenerList::getEventListener(ScriptState::current(info.GetIsolate()), v8Value, true, ListenerFindOrCreate)')
 377     elif idl_type.is_interface_type:
 378         # FIXME: should be able to eliminate WTF::getPtr in most or all cases
 379         arguments.append('WTF::getPtr(cppValue)')
 380     else:
 381         arguments.append('cppValue')
 382     if context['is_setter_raises_exception']:
 383         arguments.append('exceptionState')
 384
 385     return '%s(%s)' % (setter_name, ', '.join(arguments))
 386
 387
 388 CONTENT_ATTRIBUTE_SETTER_NAMES = {
 389     'boolean': 'setBooleanAttribute',
 390     'long': 'setIntegralAttribute',
 391     'unsigned long': 'setUnsignedIntegralAttribute',
 392 }
 393
 394
 395 def setter_base_name(interface, attribute, arguments):
 396     if 'ImplementedInPrivateScript' in attribute.extended_attributes:
 397         return '%sAttributeSetter' % uncapitalize(cpp_name(attribute))
 398
 399     if 'Reflect' not in attribute.extended_attributes:
 400         return 'set%s' % capitalize(cpp_name(attribute))
 401     arguments.append(scoped_content_attribute_name(interface, attribute))
 402
 403     base_idl_type = attribute.idl_type.base_type
 404     if base_idl_type in CONTENT_ATTRIBUTE_SETTER_NAMES:
 405         return CONTENT_ATTRIBUTE_SETTER_NAMES[base_idl_type]
 406     return 'setAttribute'
 407
 408
 409 def scoped_content_attribute_name(interface, attribute):
 410     content_attribute_name = attribute.extended_attributes['Reflect'] or attribute.name.lower()
 411     if interface.name.startswith('SVG'):
 412         # SVG's xmlbase/xmlspace/xmllang need special behavior, i.e.
 413         # it is in XMLNames namespace and the generated attribute has no xml prefix.
 414         if attribute.name.startswith('xml'):
 415             namespace = 'XMLNames'
 416             content_attribute_name = content_attribute_name[3:]
 417         else:
 418             namespace = 'SVGNames'
 419     else:
 420         namespace = 'HTMLNames'
 421     includes.add('core/%s.h' % namespace)
 422     return '%s::%sAttr' % (namespace, content_attribute_name)
 423
 424
 425 ################################################################################
 426 # Attribute configuration
 427 ################################################################################
 428
 429 # [Replaceable]
 430 def setter_callback_name(interface, attribute):
 431     cpp_class_name = cpp_name(interface)
 432     extended_attributes = attribute.extended_attributes
 433     if (('Replaceable' in extended_attributes and
 434          'PutForwards' not in extended_attributes) or
 435         is_constructor_attribute(attribute)):
 436         return '{0}V8Internal::{0}ForceSetAttributeOnThisCallback'.format(cpp_class_name)
 437     if attribute.is_read_only and 'PutForwards' not in extended_attributes:
 438         return '0'
 439     return '%sV8Internal::%sAttributeSetterCallback' % (cpp_class_name, attribute.name)
 440
 441
 442 # [DoNotCheckSecurity], [Unforgeable]
 443 def access_control_list(attribute):
 444     extended_attributes = attribute.extended_attributes
 445     access_control = []
 446     if 'DoNotCheckSecurity' in extended_attributes:
 447         do_not_check_security = extended_attributes['DoNotCheckSecurity']
 448         if do_not_check_security == 'Setter':
 449             access_control.append('v8::ALL_CAN_WRITE')
 450         else:
 451             access_control.append('v8::ALL_CAN_READ')
 452             if (not attribute.is_read_only or
 453                 'Replaceable' in extended_attributes):
 454                 access_control.append('v8::ALL_CAN_WRITE')
 455     if 'Unforgeable' in extended_attributes:
 456         access_control.append('v8::PROHIBITS_OVERWRITING')
 457     return access_control or ['v8::DEFAULT']
 458
 459
 460 # [NotEnumerable], [Unforgeable]
 461 def property_attributes(attribute):
 462     extended_attributes = attribute.extended_attributes
 463     property_attributes_list = []
 464     if ('NotEnumerable' in extended_attributes or
 465         is_constructor_attribute(attribute)):
 466         property_attributes_list.append('v8::DontEnum')
 467     if 'Unforgeable' in extended_attributes:
 468         property_attributes_list.append('v8::DontDelete')
 469     return property_attributes_list or ['v8::None']
 470
 471
 472 # [Custom], [Custom=Getter]
 473 def has_custom_getter(attribute):
 474     extended_attributes = attribute.extended_attributes
 475     return ('Custom' in extended_attributes and
 476             extended_attributes['Custom'] in [None, 'Getter'])
 477
 478
 479 # [Custom], [Custom=Setter]
 480 def has_custom_setter(attribute):
 481     extended_attributes = attribute.extended_attributes
 482     return (not attribute.is_read_only and
 483             'Custom' in extended_attributes and
 484             extended_attributes['Custom'] in [None, 'Setter'])
 485
 486
 487 ################################################################################
 488 # Constructors
 489 ################################################################################
 490
 491 idl_types.IdlType.constructor_type_name = property(
 492     # FIXME: replace this with a [ConstructorAttribute] extended attribute
 493     lambda self: strip_suffix(self.base_type, 'Constructor'))
 494
 495
 496 def is_constructor_attribute(attribute):
 497     # FIXME: replace this with [ConstructorAttribute] extended attribute
 498     return attribute.idl_type.name.endswith('Constructor')
 499
 500
 501 def constructor_getter_context(interface, attribute, context):
 502     context['needs_constructor_getter_callback'] = context['measure_as'] or context['deprecate_as']