palemoon27/dom/bindings/Configuration.py

# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this file,
# You can obtain one at http://mozilla.org/MPL/2.0/.

from WebIDL import IDLInterface, IDLExternalInterface, IDLImplementsStatement
import os
from collections import defaultdict

autogenerated_comment = "/* THIS FILE IS AUTOGENERATED - DO NOT EDIT */\n"


class Configuration:
    """
    Represents global configuration state based on IDL parse data and
    the configuration file.
    """
    def __init__(self, filename, parseData, generatedEvents=[]):

        # Read the configuration file.
        glbl = {}
        execfile(filename, glbl)
        config = glbl['DOMInterfaces']

        # Build descriptors for all the interfaces we have in the parse data.
        # This allows callers to specify a subset of interfaces by filtering
        # |parseData|.
        self.descriptors = []
        self.interfaces = {}
        self.descriptorsByName = {}
        self.optimizedOutDescriptorNames = set()
        self.generatedEvents = generatedEvents
        self.maxProtoChainLength = 0
        for thing in parseData:
            if isinstance(thing, IDLImplementsStatement):
                # Our build system doesn't support dep build involving
                # addition/removal of "implements" statements that appear in a
                # different .webidl file than their LHS interface.  Make sure we
                # don't have any of those.
                #
                # But whitelist a RHS that is LegacyQueryInterface,
                # since people shouldn't be adding any of those.
                if (thing.implementor.filename() != thing.filename() and
                    thing.implementee.identifier.name != "LegacyQueryInterface"):
                    raise TypeError(
                        "The binding build system doesn't really support "
                        "'implements' statements which don't appear in the "
                        "file in which the left-hand side of the statement is "
                        "defined.  Don't do this unless your right-hand side "
                        "is LegacyQueryInterface.\n"
                        "%s\n"
                        "%s" %
                        (thing.location, thing.implementor.location))

            assert not thing.isType()

            if not thing.isInterface():
                continue
            iface = thing
            self.interfaces[iface.identifier.name] = iface
            if iface.identifier.name not in config:
                # Completely skip consequential interfaces with no descriptor
                # if they have no interface object because chances are we
                # don't need to do anything interesting with them.
                if iface.isConsequential() and not iface.hasInterfaceObject():
                    self.optimizedOutDescriptorNames.add(iface.identifier.name)
                    continue
                entry = {}
            else:
                entry = config[iface.identifier.name]
            if not isinstance(entry, list):
                assert isinstance(entry, dict)
                entry = [entry]
            elif len(entry) == 1:
                if entry[0].get("workers", False):
                    # List with only a workers descriptor means we should
                    # infer a mainthread descriptor.  If you want only
                    # workers bindings, don't use a list here.
                    entry.append({})
                else:
                    raise TypeError("Don't use a single-element list for "
                                    "non-worker-only interface " + iface.identifier.name +
                                    " in Bindings.conf")
            elif len(entry) == 2:
                if entry[0].get("workers", False) == entry[1].get("workers", False):
                    raise TypeError("The two entries for interface " + iface.identifier.name +
                                    " in Bindings.conf should not have the same value for 'workers'")
            else:
                raise TypeError("Interface " + iface.identifier.name +
                                " should have no more than two entries in Bindings.conf")
            descs = [Descriptor(self, iface, x) for x in entry]
            self.descriptors.extend(descs)
            # Setting up descriptorsByName while iterating through interfaces
            # means we can get the nativeType of iterable interfaces without
            # having to do multiple loops.
            for d in descs:
                self.descriptorsByName.setdefault(d.interface.identifier.name,
                                                  []).append(d)

        # Keep the descriptor list sorted for determinism.
        self.descriptors.sort(lambda x, y: cmp(x.name, y.name))


        self.descriptorsByFile = {}
        for d in self.descriptors:
            self.descriptorsByFile.setdefault(d.interface.filename(),
                                              []).append(d)

        self.enums = [e for e in parseData if e.isEnum()]

        # Figure out what our main-thread and worker dictionaries and callbacks
        # are.
        mainTypes = set()
        for descriptor in ([self.getDescriptor("DummyInterface", workers=False)] +
                           self.getDescriptors(workers=False, isExternal=False, skipGen=False)):
            mainTypes |= set(getFlatTypes(getTypesFromDescriptor(descriptor)))
        (mainCallbacks, mainDictionaries) = findCallbacksAndDictionaries(mainTypes)

        workerTypes = set()
        for descriptor in ([self.getDescriptor("DummyInterfaceWorkers", workers=True)] +
                           self.getDescriptors(workers=True, isExternal=False, skipGen=False)):
            workerTypes |= set(getFlatTypes(getTypesFromDescriptor(descriptor)))
        (workerCallbacks, workerDictionaries) = findCallbacksAndDictionaries(workerTypes)

        self.dictionaries = [d for d in parseData if d.isDictionary()]
        self.callbacks = [c for c in parseData if
                          c.isCallback() and not c.isInterface()]

        # Dictionary mapping from a union type name to a set of filenames where
        # union types with that name are used.
        self.filenamesPerUnion = defaultdict(set)

        # Dictionary mapping from a filename to a list of tuples containing a
        # type and descriptor for the union types used in that file. If a union
        # type is used in multiple files then it will be added to the list
        # for the None key. Note that the list contains a tuple for every use of
        # a union type, so there can be multiple tuples with union types that
        # have the same name.
        self.unionsPerFilename = defaultdict(list)

        for (t, descriptor, _) in getAllTypes(self.descriptors, self.dictionaries, self.callbacks):
            while True:
                if t.isMozMap():
                    t = t.inner
                elif t.unroll() != t:
                    t = t.unroll()
                elif t.isPromise():
                    t = t.promiseInnerType()
                else:
                    break
            if t.isUnion():
                filenamesForUnion = self.filenamesPerUnion[t.name]
                if t.filename() not in filenamesForUnion:
                    if len(filenamesForUnion) == 0:
                        # This is the first file that we found a union with this
                        # name in, record the union as part of the file.
                        uniqueFilenameForUnion = t.filename()
                    else:
                        # We already found a file that contains a union with
                        # this name.
                        if len(filenamesForUnion) == 1:
                            # This is the first time we found a union with this
                            # name in another file.
                            for f in filenamesForUnion:
                                # Filter out unions with this name from the
                                # unions for the file where we previously found
                                # them.
                                unionsForFilename = self.unionsPerFilename[f]
                                unionsForFilename = filter(lambda u: u[0].name != t.name,
                                                           unionsForFilename)
                                if len(unionsForFilename) == 0:
                                    del self.unionsPerFilename[f]
                                else:
                                    self.unionsPerFilename[f] = unionsForFilename
                        # Unions with this name appear in multiple files, record
                        # the filename as None, so that we can detect that.
                        uniqueFilenameForUnion = None
                    self.unionsPerFilename[uniqueFilenameForUnion].append((t, descriptor))
                    filenamesForUnion.add(t.filename())

        def flagWorkerOrMainThread(items, main, worker):
            for item in items:
                if item in main:
                    item.setUserData("mainThread", True)
                if item in worker:
                    item.setUserData("workers", True)
        flagWorkerOrMainThread(self.callbacks, mainCallbacks, workerCallbacks)

    def getInterface(self, ifname):
        return self.interfaces[ifname]

    def getDescriptors(self, **filters):
        """Gets the descriptors that match the given filters."""
        curr = self.descriptors
        # Collect up our filters, because we may have a webIDLFile filter that
        # we always want to apply first.
        tofilter = []
        for key, val in filters.iteritems():
            if key == 'webIDLFile':
                # Special-case this part to make it fast, since most of our
                # getDescriptors calls are conditioned on a webIDLFile.  We may
                # not have this key, in which case we have no descriptors
                # either.
                curr = self.descriptorsByFile.get(val, [])
                continue
            elif key == 'hasInterfaceObject':
                getter = lambda x: (not x.interface.isExternal() and
                                    x.interface.hasInterfaceObject())
            elif key == 'hasInterfacePrototypeObject':
                getter = lambda x: (not x.interface.isExternal() and
                                    x.interface.hasInterfacePrototypeObject())
            elif key == 'hasInterfaceOrInterfacePrototypeObject':
                getter = lambda x: x.hasInterfaceOrInterfacePrototypeObject()
            elif key == 'isCallback':
                getter = lambda x: x.interface.isCallback()
            elif key == 'isExternal':
                getter = lambda x: x.interface.isExternal()
            elif key == 'isJSImplemented':
                getter = lambda x: x.interface.isJSImplemented()
            elif key == 'isNavigatorProperty':
                getter = lambda x: x.interface.getNavigatorProperty() is not None
            elif key == 'isExposedInAnyWorker':
                getter = lambda x: x.interface.isExposedInAnyWorker()
            elif key == 'isExposedInSystemGlobals':
                getter = lambda x: x.interface.isExposedInSystemGlobals()
            elif key == 'isExposedInWindow':
                getter = lambda x: x.interface.isExposedInWindow()
            else:
                # Have to watch out: just closing over "key" is not enough,
                # since we're about to mutate its value
                getter = (lambda attrName: lambda x: getattr(x, attrName))(key)
            tofilter.append((getter, val))
        for f in tofilter:
            curr = filter(lambda x: f[0](x) == f[1], curr)
        return curr

    def getEnums(self, webIDLFile):
        return filter(lambda e: e.filename() == webIDLFile, self.enums)

    @staticmethod
    def _filterForFileAndWorkers(items, filters):
        """Gets the items that match the given filters."""
        for key, val in filters.iteritems():
            if key == 'webIDLFile':
                items = filter(lambda x: x.filename() == val, items)
            elif key == 'workers':
                if val:
                    items = filter(lambda x: x.getUserData("workers", False), items)
                else:
                    items = filter(lambda x: x.getUserData("mainThread", False), items)
            else:
                assert(0)  # Unknown key
        return items

    def getDictionaries(self, **filters):
        return self._filterForFileAndWorkers(self.dictionaries, filters)

    def getCallbacks(self, **filters):
        return self._filterForFileAndWorkers(self.callbacks, filters)

    def getDescriptor(self, interfaceName, workers):
        """
        Gets the appropriate descriptor for the given interface name
        and the given workers boolean.
        """
        # We may have optimized out this descriptor, but the chances of anyone
        # asking about it are then slim.  Put the check for that _after_ we've
        # done our normal lookups.  But that means we have to do our normal
        # lookups in a way that will not throw if they fail.
        for d in self.descriptorsByName.get(interfaceName, []):
            if d.workers == workers:
                return d

        if workers:
            for d in self.descriptorsByName.get(interfaceName, []):
                return d

        if interfaceName in self.optimizedOutDescriptorNames:
            raise NoSuchDescriptorError(
                "No descriptor for '%s', which is a mixin ([NoInterfaceObject] "
                "and a consequential interface) without an explicit "
                "Bindings.conf annotation." % interfaceName)

        raise NoSuchDescriptorError("For " + interfaceName + " found no matches")

    def getDescriptorProvider(self, workers):
        """
        Gets a descriptor provider that can provide descriptors as needed,
        for the given workers boolean
        """
        return DescriptorProvider(self, workers)


class NoSuchDescriptorError(TypeError):
    def __init__(self, str):
        TypeError.__init__(self, str)


class DescriptorProvider:
    """
    A way of getting descriptors for interface names
    """
    def __init__(self, config, workers):
        self.config = config
        self.workers = workers

    def getDescriptor(self, interfaceName):
        """
        Gets the appropriate descriptor for the given interface name given the
        context of the current descriptor. This selects the appropriate
        implementation for cases like workers.
        """
        return self.config.getDescriptor(interfaceName, self.workers)


def methodReturnsJSObject(method):
    assert method.isMethod()
    if method.returnsPromise():
        return True

    for signature in method.signatures():
        returnType = signature[0]
        if returnType.isObject() or returnType.isSpiderMonkeyInterface():
            return True

    return False


def MemberIsUnforgeable(member, descriptor):
    # Note: "or" and "and" return either their LHS or RHS, not
    # necessarily booleans.  Make sure to return a boolean from this
    # method, because callers will compare its return value to
    # booleans.
    return bool((member.isAttr() or member.isMethod()) and
                not member.isStatic() and
                (member.isUnforgeable() or
                 descriptor.interface.getExtendedAttribute("Unforgeable")))


class Descriptor(DescriptorProvider):
    """
    Represents a single descriptor for an interface. See Bindings.conf.
    """
    def __init__(self, config, interface, desc):
        DescriptorProvider.__init__(self, config, desc.get('workers', False))
        self.interface = interface

        if self.workers:
            assert 'wantsXrays' not in desc
            self.wantsXrays = False
        else:
            self.wantsXrays = desc.get('wantsXrays', True)

        # Read the desc, and fill in the relevant defaults.
        ifaceName = self.interface.identifier.name
        # For generated iterator interfaces for other iterable interfaces, we
        # just use IterableIterator as the native type, templated on the
        # nativeType of the iterable interface. That way we can have a
        # templated implementation for all the duplicated iterator
        # functionality.
        if self.interface.isIteratorInterface():
            itrName = self.interface.iterableInterface.identifier.name
            itrDesc = self.getDescriptor(itrName)
            nativeTypeDefault = iteratorNativeType(itrDesc)

        elif self.interface.isExternal():
            assert not self.workers
            nativeTypeDefault = "nsIDOM" + ifaceName
        elif self.interface.isCallback():
            nativeTypeDefault = "mozilla::dom::" + ifaceName
        else:
            if self.workers:
                nativeTypeDefault = "mozilla::dom::workers::" + ifaceName
            else:
                nativeTypeDefault = "mozilla::dom::" + ifaceName

        self.nativeType = desc.get('nativeType', nativeTypeDefault)
        # Now create a version of nativeType that doesn't have extra
        # mozilla::dom:: at the beginning.
        prettyNativeType = self.nativeType.split("::")
        if prettyNativeType[0] == "mozilla":
            prettyNativeType.pop(0)
            if prettyNativeType[0] == "dom":
                prettyNativeType.pop(0)
        self.prettyNativeType = "::".join(prettyNativeType)

        self.jsImplParent = desc.get('jsImplParent', self.nativeType)

        # Do something sane for JSObject
        if self.nativeType == "JSObject":
            headerDefault = "js/TypeDecls.h"
        elif self.interface.isCallback() or self.interface.isJSImplemented():
            # A copy of CGHeaders.getDeclarationFilename; we can't
            # import it here, sadly.
            # Use our local version of the header, not the exported one, so that
            # test bindings, which don't export, will work correctly.
            basename = os.path.basename(self.interface.filename())
            headerDefault = basename.replace('.webidl', 'Binding.h')
        else:
            if self.workers:
                headerDefault = "mozilla/dom/workers/bindings/%s.h" % ifaceName
            elif not self.interface.isExternal() and self.interface.getExtendedAttribute("HeaderFile"):
                headerDefault = self.interface.getExtendedAttribute("HeaderFile")[0]
            elif self.interface.isIteratorInterface():
                headerDefault = "mozilla/dom/IterableIterator.h"
            else:
                headerDefault = self.nativeType
                headerDefault = headerDefault.replace("::", "/") + ".h"
        self.headerFile = desc.get('headerFile', headerDefault)
        self.headerIsDefault = self.headerFile == headerDefault
        if self.jsImplParent == self.nativeType:
            self.jsImplParentHeader = self.headerFile
        else:
            self.jsImplParentHeader = self.jsImplParent.replace("::", "/") + ".h"

        self.skipGen = desc.get('skipGen', False)

        self.notflattened = desc.get('notflattened', False)
        self.register = desc.get('register', True)

        self.hasXPConnectImpls = desc.get('hasXPConnectImpls', False)

        # If we're concrete, we need to crawl our ancestor interfaces and mark
        # them as having a concrete descendant.
        self.concrete = (not self.interface.isExternal() and
                         not self.interface.isCallback() and
                         desc.get('concrete', True))
        self.hasUnforgeableMembers = (self.concrete and
                                      any(MemberIsUnforgeable(m, self) for m in
                                          self.interface.members))
        self.operations = {
            'IndexedGetter': None,
            'IndexedSetter': None,
            'IndexedCreator': None,
            'IndexedDeleter': None,
            'NamedGetter': None,
            'NamedSetter': None,
            'NamedCreator': None,
            'NamedDeleter': None,
            'Stringifier': None,
            'LegacyCaller': None,
            'Jsonifier': None
            }

        # Stringifiers and jsonifiers need to be set up whether an interface is
        # concrete or not, because they're actually prototype methods and hence
        # can apply to instances of descendant interfaces.  Legacy callers and
        # named/indexed operations only need to be set up on concrete
        # interfaces, since they affect the JSClass we end up using, not the
        # prototype object.
        def addOperation(operation, m):
            if not self.operations[operation]:
                self.operations[operation] = m

        # Since stringifiers go on the prototype, we only need to worry
        # about our own stringifier, not those of our ancestor interfaces.
        if not self.interface.isExternal():
            for m in self.interface.members:
                if m.isMethod() and m.isStringifier():
                    addOperation('Stringifier', m)
                if m.isMethod() and m.isJsonifier():
                    addOperation('Jsonifier', m)

        if self.concrete:
            self.proxy = False
            iface = self.interface
            for m in iface.members:
                # Don't worry about inheriting legacycallers either: in
                # practice these are on most-derived prototypes.
                if m.isMethod() and m.isLegacycaller():
                    if not m.isIdentifierLess():
                        raise TypeError("We don't support legacycaller with "
                                        "identifier.\n%s" % m.location)
                    if len(m.signatures()) != 1:
                        raise TypeError("We don't support overloaded "
                                        "legacycaller.\n%s" % m.location)
                    addOperation('LegacyCaller', m)
            while iface:
                for m in iface.members:
                    if not m.isMethod():
                        continue

                    def addIndexedOrNamedOperation(operation, m):
                        if m.isIndexed():
                            operation = 'Indexed' + operation
                        else:
                            assert m.isNamed()
                            operation = 'Named' + operation
                        addOperation(operation, m)

                    if m.isGetter():
                        addIndexedOrNamedOperation('Getter', m)
                    if m.isSetter():
                        addIndexedOrNamedOperation('Setter', m)
                    if m.isCreator():
                        addIndexedOrNamedOperation('Creator', m)
                    if m.isDeleter():
                        addIndexedOrNamedOperation('Deleter', m)
                    if m.isLegacycaller() and iface != self.interface:
                        raise TypeError("We don't support legacycaller on "
                                        "non-leaf interface %s.\n%s" %
                                        (iface, iface.location))

                iface.setUserData('hasConcreteDescendant', True)
                iface = iface.parent

            self.proxy = (self.supportsIndexedProperties() or
                          (self.supportsNamedProperties() and
                           not self.hasNamedPropertiesObject))

            if self.proxy:
                if (not self.operations['IndexedGetter'] and
                    (self.operations['IndexedSetter'] or
                     self.operations['IndexedDeleter'] or
                     self.operations['IndexedCreator'])):
                    raise SyntaxError("%s supports indexed properties but does "
                                      "not have an indexed getter.\n%s" %
                                      (self.interface, self.interface.location))
                if (not self.operations['NamedGetter'] and
                    (self.operations['NamedSetter'] or
                     self.operations['NamedDeleter'] or
                     self.operations['NamedCreator'])):
                    raise SyntaxError("%s supports named properties but does "
                                      "not have a named getter.\n%s" %
                                      (self.interface, self.interface.location))
                iface = self.interface
                while iface:
                    iface.setUserData('hasProxyDescendant', True)
                    iface = iface.parent

        if desc.get('wantsQI', None) is not None:
            self._wantsQI = desc.get('wantsQI', None)
        self.wrapperCache = (not self.interface.isCallback() and
                             not self.interface.isIteratorInterface() and
                             desc.get('wrapperCache', True))

        def make_name(name):
            return name + "_workers" if self.workers else name
        self.name = make_name(interface.identifier.name)

        # self.extendedAttributes is a dict of dicts, keyed on
        # all/getterOnly/setterOnly and then on member name. Values are an
        # array of extended attributes.
        self.extendedAttributes = {'all': {}, 'getterOnly': {}, 'setterOnly': {}}

        def addExtendedAttribute(attribute, config):
            def add(key, members, attribute):
                for member in members:
                    self.extendedAttributes[key].setdefault(member, []).append(attribute)

            if isinstance(config, dict):
                for key in ['all', 'getterOnly', 'setterOnly']:
                    add(key, config.get(key, []), attribute)
            elif isinstance(config, list):
                add('all', config, attribute)
            else:
                assert isinstance(config, str)
                if config == '*':
                    iface = self.interface
                    while iface:
                        add('all', map(lambda m: m.name, iface.members), attribute)
                        iface = iface.parent
                else:
                    add('all', [config], attribute)

        if self.interface.isJSImplemented():
            addExtendedAttribute('implicitJSContext', ['constructor'])
        else:
            for attribute in ['implicitJSContext']:
                addExtendedAttribute(attribute, desc.get(attribute, {}))

        self._binaryNames = desc.get('binaryNames', {})
        self._binaryNames.setdefault('__legacycaller', 'LegacyCall')
        self._binaryNames.setdefault('__stringifier', 'Stringify')

        if not self.interface.isExternal():
            self.anypermissions = dict()
            self.allpermissions = dict()

            # Adds a permission list to this descriptor and returns the index to use.
            def addPermissions(ifaceOrMember, attribute):
                if attribute == "CheckAllPermissions":
                    permissions = self.allpermissions
                else:
                    permissions = self.anypermissions

                checkPermissions = ifaceOrMember.getExtendedAttribute(attribute)
                if checkPermissions is None:
                    return None

                # It's a list of whitespace-separated strings
                assert(len(checkPermissions) is 1)
                assert(checkPermissions[0] is not None)
                checkPermissions = checkPermissions[0]
                permissionsList = checkPermissions.split()
                if len(permissionsList) == 0:
                    raise TypeError("Need at least one permission name for %s" % attribute)

                permissionsList = tuple(sorted(set(permissionsList)))
                return permissions.setdefault(permissionsList, len(permissions))

            self.checkAnyPermissionsIndex = addPermissions(self.interface, "CheckAnyPermissions")
            self.checkAnyPermissionsIndicesForMembers = dict()
            self.checkAllPermissionsIndex = addPermissions(self.interface, "CheckAllPermissions")
            self.checkAllPermissionsIndicesForMembers = dict()
            for m in self.interface.members:
                permissionsIndex = addPermissions(m, "CheckAnyPermissions")
                if permissionsIndex is not None:
                    self.checkAnyPermissionsIndicesForMembers[m.identifier.name] = permissionsIndex
                allpermissionsIndex = addPermissions(m, "CheckAllPermissions")
                if allpermissionsIndex is not None:
                    self.checkAllPermissionsIndicesForMembers[m.identifier.name] = allpermissionsIndex

            def isTestInterface(iface):
                return (iface.identifier.name in ["TestInterface",
                                                  "TestJSImplInterface",
                                                  "TestRenamedInterface"])

            self.featureDetectibleThings = set()
            if not isTestInterface(self.interface):
                if (self.interface.getExtendedAttribute("CheckAnyPermissions") or
                    self.interface.getExtendedAttribute("CheckAllPermissions") or
                    self.interface.getExtendedAttribute("AvailableIn") == "PrivilegedApps"):
                    if self.interface.getNavigatorProperty():
                        self.featureDetectibleThings.add("Navigator.%s" % self.interface.getNavigatorProperty())
                    else:
                        iface = self.interface.identifier.name
                        self.featureDetectibleThings.add(iface)
                        for m in self.interface.members:
                            self.featureDetectibleThings.add("%s.%s" % (iface, m.identifier.name))

                for m in self.interface.members:
                    if (m.getExtendedAttribute("CheckAnyPermissions") or
                        m.getExtendedAttribute("CheckAllPermissions") or
                        m.getExtendedAttribute("AvailableIn") == "PrivilegedApps"):
                        self.featureDetectibleThings.add("%s.%s" % (self.interface.identifier.name, m.identifier.name))

            for member in self.interface.members:
                if not member.isAttr() and not member.isMethod():
                    continue
                binaryName = member.getExtendedAttribute("BinaryName")
                if binaryName:
                    assert isinstance(binaryName, list)
                    assert len(binaryName) == 1
                    self._binaryNames.setdefault(member.identifier.name,
                                                 binaryName[0])

        # Build the prototype chain.
        self.prototypeChain = []
        parent = interface
        while parent:
            self.prototypeChain.insert(0, parent.identifier.name)
            parent = parent.parent
        config.maxProtoChainLength = max(config.maxProtoChainLength,
                                         len(self.prototypeChain))

    def binaryNameFor(self, name):
        return self._binaryNames.get(name, name)

    @property
    def prototypeNameChain(self):
        return map(lambda p: self.getDescriptor(p).name, self.prototypeChain)

    @property
    def parentPrototypeName(self):
        if len(self.prototypeChain) == 1:
            return None
        return self.getDescriptor(self.prototypeChain[-2]).name

    def hasInterfaceOrInterfacePrototypeObject(self):

        # Forward-declared interfaces don't need either interface object or
        # interface prototype object as they're going to use QI (on main thread)
        # or be passed as a JSObject (on worker threads).
        if self.interface.isExternal():
            return False

        return self.interface.hasInterfaceObject() or self.interface.hasInterfacePrototypeObject()

    @property
    def hasNamedPropertiesObject(self):
        if self.interface.isExternal():
            return False

        return self.isGlobal() and self.supportsNamedProperties()

    def getExtendedAttributes(self, member, getter=False, setter=False):
        def ensureValidThrowsExtendedAttribute(attr):
            assert(attr is None or attr is True or len(attr) == 1)
            if (attr is not None and attr is not True and
                'Workers' not in attr and 'MainThread' not in attr):
                raise TypeError("Unknown value for 'Throws': " + attr[0])

        def maybeAppendInfallibleToAttrs(attrs, throws):
            ensureValidThrowsExtendedAttribute(throws)
            if (throws is None or
                (throws is not True and
                 ('Workers' not in throws or not self.workers) and
                 ('MainThread' not in throws or self.workers))):
                attrs.append("infallible")

        name = member.identifier.name
        throws = self.interface.isJSImplemented() or member.getExtendedAttribute("Throws")
        if member.isMethod():
            # JSObject-returning [NewObject] methods must be fallible,
            # since they have to (fallibly) allocate the new JSObject.
            if (member.getExtendedAttribute("NewObject") and
                methodReturnsJSObject(member)):
                throws = True
            attrs = self.extendedAttributes['all'].get(name, [])
            maybeAppendInfallibleToAttrs(attrs, throws)
            return attrs

        assert member.isAttr()
        assert bool(getter) != bool(setter)
        key = 'getterOnly' if getter else 'setterOnly'
        attrs = self.extendedAttributes['all'].get(name, []) + self.extendedAttributes[key].get(name, [])
        if throws is None:
            throwsAttr = "GetterThrows" if getter else "SetterThrows"
            throws = member.getExtendedAttribute(throwsAttr)
        maybeAppendInfallibleToAttrs(attrs, throws)
        return attrs

    def supportsIndexedProperties(self):
        return self.operations['IndexedGetter'] is not None

    def supportsNamedProperties(self):
        return self.operations['NamedGetter'] is not None

    def needsConstructHookHolder(self):
        assert self.interface.hasInterfaceObject()
        return False

    def needsHeaderInclude(self):
        """
        An interface doesn't need a header file if it is not concrete, not
        pref-controlled, has no prototype object, has no static methods or
        attributes and has no parent.  The parent matters because we assert
        things about refcounting that depend on the actual underlying type if we
        have a parent.

        """
        return (self.interface.isExternal() or self.concrete or
                self.interface.hasInterfacePrototypeObject() or
                any((m.isAttr() or m.isMethod()) and m.isStatic() for m in self.interface.members) or
                self.interface.parent)

    def hasThreadChecks(self):
        return ((self.isExposedConditionally() and
                 not self.interface.isExposedInWindow()) or
                self.interface.isExposedInSomeButNotAllWorkers())

    def isExposedConditionally(self):
        return (self.interface.isExposedConditionally() or
                self.interface.isExposedInSomeButNotAllWorkers())

    def needsXrayResolveHooks(self):
        """
        Generally, any interface with NeedResolve needs Xray
        resolveOwnProperty and enumerateOwnProperties hooks.  But for
        the special case of plugin-loading elements, we do NOT want
        those, because we don't want to instantiate plug-ins simply
        due to chrome touching them and that's all those hooks do on
        those elements.  So we special-case those here.
        """
        return (self.interface.getExtendedAttribute("NeedResolve") and
                self.interface.identifier.name not in ["HTMLObjectElement",
                                                       "HTMLEmbedElement",
                                                       "HTMLAppletElement"])

    def needsSpecialGenericOps(self):
        """
        Returns true if this descriptor requires generic ops other than
        GenericBindingMethod/GenericBindingGetter/GenericBindingSetter.

        In practice we need to do this if our this value might be an XPConnect
        object or if we need to coerce null/undefined to the global.
        """
        return self.hasXPConnectImpls or self.interface.isOnGlobalProtoChain()

    def isGlobal(self):
        """
        Returns true if this is the primary interface for a global object
        of some sort.
        """
        return (self.interface.getExtendedAttribute("Global") or
                self.interface.getExtendedAttribute("PrimaryGlobal"))


# Some utility methods
def getTypesFromDescriptor(descriptor):
    """
    Get all argument and return types for all members of the descriptor
    """
    members = [m for m in descriptor.interface.members]
    if descriptor.interface.ctor():
        members.append(descriptor.interface.ctor())
    members.extend(descriptor.interface.namedConstructors)
    signatures = [s for m in members if m.isMethod() for s in m.signatures()]
    types = []
    for s in signatures:
        assert len(s) == 2
        (returnType, arguments) = s
        types.append(returnType)
        types.extend(a.type for a in arguments)

    types.extend(a.type for a in members if a.isAttr())
    return types


def getFlatTypes(types):
    retval = set()
    for type in types:
        type = type.unroll()
        if type.isUnion():
            retval |= set(type.flatMemberTypes)
        else:
            retval.add(type)
    return retval


def getTypesFromDictionary(dictionary):
    """
    Get all member types for this dictionary
    """
    types = []
    curDict = dictionary
    while curDict:
        types.extend([m.type for m in curDict.members])
        curDict = curDict.parent
    return types


def getTypesFromCallback(callback):
    """
    Get the types this callback depends on: its return type and the
    types of its arguments.
    """
    sig = callback.signatures()[0]
    types = [sig[0]]  # Return type
    types.extend(arg.type for arg in sig[1])  # Arguments
    return types


def findCallbacksAndDictionaries(inputTypes):
    """
    Ensure that all callbacks and dictionaries reachable from types end up in
    the returned callbacks and dictionaries sets.

    Note that we assume that our initial invocation already includes all types
    reachable via descriptors in "types", so we only have to deal with things
    that are themeselves reachable via callbacks and dictionaries.
    """
    def doFindCallbacksAndDictionaries(types, callbacks, dictionaries):
        unhandledTypes = set()
        for type in types:
            if type.isCallback() and type.callback not in callbacks:
                unhandledTypes |= getFlatTypes(getTypesFromCallback(type.callback))
                callbacks.add(type.callback)
            elif type.isDictionary() and type.inner not in dictionaries:
                d = type.inner
                unhandledTypes |= getFlatTypes(getTypesFromDictionary(d))
                while d:
                    dictionaries.add(d)
                    d = d.parent
        if len(unhandledTypes) != 0:
            doFindCallbacksAndDictionaries(unhandledTypes, callbacks, dictionaries)

    retCallbacks = set()
    retDictionaries = set()
    doFindCallbacksAndDictionaries(inputTypes, retCallbacks, retDictionaries)
    return (retCallbacks, retDictionaries)


def getAllTypes(descriptors, dictionaries, callbacks):
    """
    Generate all the types we're dealing with.  For each type, a tuple
    containing type, descriptor, dictionary is yielded.  The
    descriptor and dictionary can be None if the type does not come
    from a descriptor or dictionary; they will never both be non-None.
    """
    for d in descriptors:
        if d.interface.isExternal():
            continue
        for t in getTypesFromDescriptor(d):
            yield (t, d, None)
    for dictionary in dictionaries:
        for t in getTypesFromDictionary(dictionary):
            yield (t, None, dictionary)
    for callback in callbacks:
        for t in getTypesFromCallback(callback):
            yield (t, None, None)

def iteratorNativeType(descriptor):
    assert descriptor.interface.isIterable()
    iterableDecl = descriptor.interface.maplikeOrSetlikeOrIterable
    if iterableDecl.valueType is None:
        iterClass = "OneTypeIterableIterator"
    else:
        iterClass = "TwoTypeIterableIterator"
    return "mozilla::dom::%s<%s>" % (iterClass, descriptor.nativeType)